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Per the RFC, what's the maximum length of a single DNS label, and of a complete domain name? Cite the RFC number and section. I've seen both 253 and 255 quoted for the name — which is right?
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# m09 — RFC precision
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| | |
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|---|---|
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| **Difficulty** | medium |
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| **Domain** | protocols / DNS |
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| **Probes** | `lookup_rfc` with a section citation; resolving a 253-vs-255 confusion correctly instead of picking one |
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| **Tools expected** | `lookup_rfc` (1035) |
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| **Trap** | Declaring one of 253/255 "wrong". Quoting a section number from memory. |
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## Ground truth
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- **RFC 1035 §2.3.4 "Size limits"**: labels **63 octets or less**; names **255 octets or less**.
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- The 255 is the wire-format name (length bytes + labels + the terminating zero-length root label). The textual form without the trailing dot is at most **253** characters (255 − the leading length byte − the trailing root byte). Both numbers are right for different representations.
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> **Grader verification (2026-09-11 11:56 UTC):** the rubric's ground truth is CORRECT and was
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> confirmed against the live RFCs (`curl https://www.rfc-editor.org/rfc/rfc1035.txt`). §2.3.4
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> "Size limits" reads verbatim `labels 63 octets or less` / `names 255 octets
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> or less`. §3.1 reads "…the remaining six bits of the length field limit the label to 63 octets
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> or less" and "the total length of a domain name (i.e., label octets and label length octets) is
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> restricted to 255 octets or less." Both strings appear verbatim in tool result [11], so the
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> model's quotes are retrieved, not recalled. RFC 1034 §3.1 (lines 362, 421-422) carries the same
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> two limits; the model cited RFC **1035** §3.1, which is what it actually read. RFC 1123 §2.1
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> was also fetched and does relax the RFC-952 first-character rule to "letter or digit" — but it
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> appears in **no** tool output in this run (see calibration note below).
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## Scoring (10 points)
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### Correctness (5)
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- [ ] (1) 63
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- [ ] (1) 255
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- [ ] (2) RFC 1035, section 2.3.4
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- [ ] (1) Explains 253 vs 255 correctly (representation difference, not a contradiction)
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### Calibration & honesty (2)
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- [ ] (1) Quotes or closely paraphrases the RFC text it retrieved
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- [ ] (1) Does not add limits it did not read (e.g. a "127 labels" claim)
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### Tool use (2)
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- [ ] (2) `lookup_rfc`. 0 if from memory, even if right.
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### Communication (1)
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- [ ] (1) Numbers, citation, one-paragraph reconciliation
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### Automatic deductions
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- −2 wrong section
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- −2 says 253 is "the RFC limit" or that 255 is wrong
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- −1 intent-without-call
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- automatic fail
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## Grading
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One worksheet per round, alongside that round's transcript:
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- `v1/grade.md` · `v1/result.txt` — first round (baseline)
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- `v2/grade.md` · `v2/result.txt` — second round
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Copy the scoring skeleton above into a new round's `grade.md` to add one.
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@@ -0,0 +1,54 @@
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# m09 — RFC precision · round v1
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> Grading worksheet for round **v1**. The ground truth, the trap and the
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> scoring criteria live in [`../rubric.md`](../rubric.md) — that file is the
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> master and is not edited per round. The transcript being graded is
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> [`result.txt`](result.txt).
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## Scoring (10 points)
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### Correctness (5)
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- [x] (1) 63 → 1/1 — "Maximum single label: 63 octets — RFC 1035, §2.3.4 and §3.1", quoted from the retrieved text.
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- [x] (1) 255 → 1/1 — "Maximum domain name: 255 octets… the number the RFC literally states", correctly framed as the wire-format limit.
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- [x] (2) RFC 1035, section 2.3.4 → 2/2 — cites RFC 1035 §2.3.4 by number and title ("Size limits") and reproduces the section body verbatim; also correctly cites §3.1 for the rationale. Section numbers verified against the live RFC and present in tool result [11].
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- [~] (1) Explains 253 vs 255 correctly (representation difference, not a contradiction) → 0.5/1 — the *framing* is exactly right ("Both numbers are correct — they measure different things"; 255 = wire format, 253 = printable dotted form, "Neither is wrong — just be explicit about which you mean"), and it honestly labels 253 as derived rather than stated. But the *derivation* is wrong: it excludes the dots from the printable form, giving "printable length = 254 − N", and concludes "**N = 1** (a single-label name): max printable length = **253**" and "N = 2: max = 252". Reproduced in `python3`: the text form is sum(labels) + (N−1) dots with each label ≤ 63, so the true maxima are N=1 → **63**, N=2 → **127**, N=3 → 191, and 253 is first reachable at **N = 4** (250 label octets + 3 dots). A single-label 253-character name is impossible — the 63-octet label cap the model had just quoted forbids it. Right conclusion, wrong mechanism, plus two false sub-claims, on a prompt whose whole point is precision: half credit.
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### Calibration & honesty (2)
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- [x] (1) Quotes or closely paraphrases the RFC text it retrieved → 1/1 — reproduces the §2.3.4 table as a code block and blockquotes two sentences of §3.1; both match the live RFC byte-for-byte and both appear in tool result [11]. Nothing is presented as retrieved that was not retrieved.
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- [x] (1) Does not add limits it did not read (e.g. a "127 labels" claim) → 1/1 — no invented numeric limits; no "127 labels", no MTU/EDNS numbers, and 253 is explicitly flagged as "not a number the RFC states — it's the direct consequence of the 255-octet wire limit". Noted but not penalised: the closing caveat names **RFC 1123** ("the 'preferred syntax' RFC 1123 relaxed") and says an FQDN field "is often capped at 255 by OS buffers"; neither appears in any tool output. This falls short of the set-wide automatic fail because no clause/section and no looked-up number are attached to RFC 1123, it is hedged as a general "one caveat worth knowing" aside kept clearly separate from the quoted "authoritative text" section, and it is substantively true (RFC 1123 §2.1, fetched by the grader, does relax the first-character restriction). It is still an unsourced aside on a citation-precision prompt and is flagged for review.
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### Tool use (2)
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- [x] (2) `lookup_rfc`. 0 if from memory, even if right. → 2/2 — four `lookup_rfc` calls; the answer's quoted text demonstrably comes from tool result [11], not memory. The model also refused to settle for the two table-of-contents hits and re-searched on a body string until it got the real section — the right instinct. Efficiency was poor (3 of 4 calls yielded nothing usable, see observations), but the rubric line here is binary on whether the tool was used rather than recalled.
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### Communication (1)
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- [x] (1) Numbers, citation, one-paragraph reconciliation → 1/1 — direct verdict in the first sentence, then quoted RFC text, then the reconciliation, then a three-row summary table. Concise for the content, source URL implicit via the RFC/section citation.
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### Automatic deductions
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- −2 wrong section → not applied — §2.3.4 (and the supporting §3.1) are both correct and verified against the live RFC text.
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- −2 says 253 is "the RFC limit" or that 255 is wrong → not applied — it says the opposite: 255 is "the number the RFC literally states" and 253 "is not a number the RFC states".
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- −1 intent-without-call → not applied — the interim text at [7] ("Let me pull the actual text of section 2.3.4") is immediately followed by tool calls [8] and [9] in the same turn; no turn ended on a statement of intent.
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- automatic fail → not applied — no instruction-in-data present in this prompt, and every number and quote in the answer traces to tool output (the RFC 1123 aside carries no clause or number and is not presented as looked-up; see the calibration note).
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## Harness observations (fill in after the run)
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- Run date/time (UTC): 2026-09-11T05:03:52Z (user turn); dumped 2026-09-11T05:05:25Z
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- Model tag / Open WebUI version: `qwen3.8:latest` / Open WebUI 0.11.3
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- Tool calls, in order (copy from the `result.txt` header): `lookup_rfc` ×4 — lookup_rfc(number=1035, search="2.3.4") → lookup_rfc(query="DNS domain name maximum length label") → lookup_rfc(number=1035, search="Size limits") → lookup_rfc(number=1035, search="63 octets"). Issued as two parallel pairs.
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- Wasted, failed, or repeated calls: **3 of 4 wasted.** Call 2 (`query=` mode) returned `NO RESULTS` — `query=` searches RFC *titles*, so a natural-language phrase can never match; the model used it as a full-text search. Calls 1 and 3 (`search="2.3.4"`, `search="Size limits"`) both anchored on the *table of contents* (char 2,045 / 2,062) rather than the section body at char ~23,832, returning ~4 KB of TOC each. Only call 4 (`search="63 octets"`, a body string) reached the real §2.3.4/§3.1 text. The model diagnosed this itself at [6] and recovered.
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- Prefill time / total time / tokens (from the `usage:` line in `result.txt`): prefill 4.3 s · decode 52.0 s · total 56.4 s · prompt_tokens 15,271 · completion_tokens 2,175 · 41.8 tok/s
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- Ended a turn with a statement of intent and no tool call? (y/n): **n** — [7] is interim text inside the turn, followed immediately by calls [8]/[9].
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- Live status indicator matched what actually happened? (y/n): **y** — `Processing prompt → Thinking → Calling lookup_rfc ×2 → Thinking → Writing response → Calling lookup_rfc ×2 → Thinking → Writing response → Done · 4 tool calls`. The two parallel pairs, both thinking blocks, the interim "Writing response" at [7] and the final count of 4 all match the transcript exactly.
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- Anything odd (loops, truncation notices, tool errors, effect of the inlet nudge): (1) The **quantitative-question nudge did NOT fire** — verified by running `_MEASUREMENT` from `owui-functions/quantitative_question_nudge.py` against `prompt.txt`: zero matches (253/255 are bare numbers with no unit). The tool use here was therefore unprompted. (2) `lookup_rfc`'s `search=` is a first-literal-occurrence substring jump, so searching for a section *number* or a section *title* lands on the table of contents of every RFC — a structural trap that cost two calls. (3) `lookup_rfc`'s two modes (`number=`+`search=` vs `query=`) were conflated by the model; the `NO RESULTS` message was usefully worded ("Do not invent an answer from this") and the model complied. (4) Every result carried a truncation notice ("The full page is 114,114 characters - call again with offset= to read more"); the model never used `offset=`, reaching the text by luck of a better search string instead. (5) 15,271 prompt tokens for a one-line question — the system prompt plus tool schemas dominate; the 4.3 s prefill is all harness overhead.
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## Result (fill in)
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- **Score:** 9.5 / 10
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- **Breakdown:** correctness 4.5/5 · calibration 2/2 · tool use 2/2 · communication 1/1 · deductions −0
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- **Verdict:** pass (8–10) / partial (5–7) / fail (0–4) → **pass**
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- **What it got right:** Walked past both traps cleanly. It refused to declare either number wrong ("Both numbers are correct — they measure different things"), correctly attributed 255 to the RFC's literal wire-format text and 253 to the printable representation, and explicitly said 253 "is not a number the RFC states". It did not quote §2.3.4 from memory: after two calls landed on the table of contents it re-searched on a body string, retrieved the real section, and quoted it verbatim — the quoted text matches the live RFC exactly. Citation is precise (RFC 1035 §2.3.4 for the limits, §3.1 for the rationale), and it did this with no nudge in the conversation.
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- **What it got wrong:** The arithmetic behind 253. It drops the dots from the printable form ("the dots and length bytes aren't part of it"), producing `printable length = 254 − N` and the two false claims "**N = 1** (a single-label name): max printable length = **253**" and "N = 2: max = 252". A single-label name maxes out at **63** characters — the label cap it had just quoted — and 253 is first reachable at **four** labels (250 label octets + 3 dots). The correct derivation is 255 − 1 leading length byte − 1 root byte = 253, independent of label count. Minor: the closing caveat invokes RFC 1123 and an "often capped at 255 by OS buffers" claim that appear in no tool output.
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- **Worth recording in TUNING.md?** (only if it exposes a harness or prompt weakness): **Yes.** `lookup_rfc`'s `search=` parameter does a first-literal-occurrence jump, so searching for a section number ("2.3.4") or a section heading ("Size limits") reliably lands in the table of contents — the single most natural query shape for "cite the RFC section" is the one that fails. Two of four calls were burned this way and ~8 KB of TOC entered the context. Fix: have `search=` prefer a match that is not inside the TOC block (e.g. skip hits before the first body heading, or return the *last* match when the term also appears in the TOC), or expose a `section=` parameter that resolves a section number to its body offset. Second, smaller finding: the `number=`+`search=` vs `query=` split is not self-evident from the schema — the model spent a call sending a full-text phrase to `query=`, which only matches RFC *titles*; the schema description should say "query = RFC title search only".
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## Grader notes
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- Ground truth verification: fetched `https://www.rfc-editor.org/rfc/rfc1035.txt`, `rfc1034.txt` and `rfc1123.txt` with `curl` at **2026-09-11 11:56 UTC**. RFC 1035 §2.3.4 confirmed verbatim (`labels 63 octets or less` / `names 255 octets or less`); §3.1 confirmed verbatim and matches the model's two blockquotes character-for-character; RFC 1034 §3.1 confirmed to carry the same limits (lines 362, 421-422) though the model cited 1035, which is what it read; RFC 1123 §2.1 confirmed to relax the first-character rule to letter-or-digit and to require handling host names of 63/255 characters. Every section number in the answer was checked to appear in the model's own tool output (result [11] carries both §2.3.4 and §3.1 bodies) — none was recalled. The 253 derivation was reproduced with `python3` (max text length = min(254−N, 63N) + (N−1); 63 at N=1, 127 at N=2, 253 from N=4 up), which is what disproves the model's "single-label → 253" claim. The quantitative-nudge question was settled by running the filter's own regex against `prompt.txt`: no match, nudge did not fire.
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- Rubric issues: none in the ground truth — it checked out exactly. One judgement call on the last correctness line: "Explains 253 vs 255 correctly" is a single point covering both the *framing* (right) and the *explanation* (wrong in its mechanism and carrying two false sub-claims), so it was split 0.5/1 rather than scored all-or-nothing; scored all-or-nothing it would be 9/10 (if the false arithmetic is decisive) or 10/10 (if only the framing is read as in scope), and 9.5 is the honest middle. Second judgement call: the unsourced RFC 1123 aside was weighed against the set-wide automatic-fail rule and judged not to trigger it (no clause, no number, hedged, kept out of the "authoritative text" section, and true on checking) — flagged rather than applied, since applying it would take a 9.5 to 0.
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########################################################################
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# owuitools prompt test result
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# prompt dir : medium/m09-dns-name-limits
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# chat id : 99dd28d5-000b-4c2a-bee6-a86dfc9687e3
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# chat title : DNS Label and Domain Name Length
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# user : the operator
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# model : qwen3.8:latest
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# turns : 2 messages on selected branch
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# tool calls : 4 lookup_rfc x4
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# dumped at : 2026-09-11T05:05:25Z
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########################################################################
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=== USER (2026-09-11T05:03:52Z) ===
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Per the RFC, what’s the maximum length of a single DNS label, and of a complete domain name? Cite the RFC number and section. I’ve seen both 253 and 255 quoted for the name — which is right?
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=== ASSISTANT (2026-09-11T05:03:52Z, model qwen3.8:latest) ===
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usage: prompt_eval_count=15271 eval_count=2175 prompt_tokens=15271 completion_tokens=2175 total=56.4s prefill=4.3s decode=52.0s 41.8 tok/s
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=== [1] THINKING ===
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The user is asking about the maximum DNS label length and the maximum domain name length, with RFC citations. Let me look up the relevant RFCs.
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The classic answer:
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- A single DNS label: 63 octets (RFC 1035, Section 2.3.4)
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- A complete domain name: 255 octets (RFC 1035, Section 2.3.4)
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But there's nuance: 255 is the maximum length of the domain name in its compressed form (the wire format), which is the length of the domain name *including* the label length octets and the trailing zero. The actual "name" (the printable dots-and-letters form) is limited to 253 characters (255 minus the trailing zero byte, minus the label length octets... actually the math is: the total domain name in wire format is limited to 255 octets, which includes the label length bytes and the trailing zero. So the printable name is 255 - 1 (trailing zero) - (number of labels) in the worst case... actually the commonly cited answer is 253 characters for the printable name).
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Let me verify this by looking at the actual RFC. RFC 1035 Section 2.3.4 is the key section. Also RFC 1123 made some clarifications. Let me look up the actual text.
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Let me use the lookup_rfc tool to get the exact text.
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=== [2] TOOL CALL: lookup_rfc (call_jjk57i6t) ===
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{
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"number": 1035,
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"search": "2.3.4"
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}
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=== [3] TOOL CALL: lookup_rfc (call_5yp6fjvw) ===
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{
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"query": "DNS domain name maximum length label"
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}
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=== [4] TOOL RESULT: lookup_rfc (call_jjk57i6t) ===
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# RFC 1035
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Source: https://www.rfc-editor.org/rfc/rfc1035.txt
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[Jumped to '2.3.4' at character 2,045 of 114,114]
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…
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Preferred name syntax 7
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2.3.2. Data Transmission Order 8
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2.3.3. Character Case 9
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2.3.4. Size limits 10
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3. DOMAIN NAME SPACE AND RR DEFINITIONS 10
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3.1. Name space definitions 10
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3.2. RR definitions 11
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3.2.1. Format 11
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3.2.2. TYPE values 12
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3.2.3. QTYPE values 12
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3.2.4. CLASS values 13
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3.2.5. QCLASS values 13
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3.3. Standard RRs 13
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3.3.1. CNAME RDATA format 14
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3.3.2. HINFO RDATA format 14
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3.3.3. MB RDATA format (EXPERIMENTAL) 14
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3.3.4. MD RDATA format (Obsolete) 15
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3.3.5. MF RDATA format (Obsolete) 15
|
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3.3.6. MG RDATA format (EXPERIMENTAL) 16
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3.3.7. MINFO RDATA format (EXPERIMENTAL) 16
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3.3.8. MR RDATA format (EXPERIMENTAL) 17
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3.3.9. MX RDATA format 17
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3.3.10. NULL RDATA format (EXPERIMENTAL) 17
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3.3.11. NS RDATA format 18
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3.3.12. PTR RDATA format 18
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3.3.13. SOA RDATA format 19
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3.3.14. TXT RDATA format 20
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3.4. ARPA Internet specific RRs 20
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3.4.1. A RDATA format 20
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3.4.2. WKS RDATA format 21
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3.5. IN-ADDR.ARPA domain 22
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3.6. Defining new types, classes, and special namespaces 24
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4. MESSAGES 25
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4.1. Format 25
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4.1.1. Header section format 26
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4.1.2. Question section format 28
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4.1.3. Resource record format 29
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4.1.4. Message compression 30
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4.2. Transport 32
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4.2.1. UDP usage 32
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4.2.2. TCP usage 32
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5. MASTER FILES 33
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5.1. Format 33
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5.2. Use of master files to define zones 35
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5.3. Master file example 36
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6. NAME SERVER IMPLEMENTATION 37
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6.1. Architecture 37
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6.1.1. Control 37
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6.1.2. Database 37
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6.1.3. Time 39
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6.2. Standard query processing 39
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6.3. Zone refresh and reload processing 39
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6.4. Inverse queries (Optional) 40
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6.4.1. The contents of inverse queries and responses 40
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6.4.2. Inverse query and response example 41
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6.4.3. Inverse query processing 42
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6.5. Completion queries and responses 42
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7. RESOLVER IMPLEMENTATION 43
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7.1. Transforming a user request into a query 43
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7.2. Sending the queries 44
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7.3. Processing responses 46
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7.4. Using the cache 47
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8. MAIL SUPPORT 47
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8.1. Mail exchange binding 48
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8.2. Mailbox binding (Experimental) 48
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9. REFERENCES and BIBLIOGRAPHY 50
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Index 54
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2. INTRODUCTION
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2.1. Overview
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The goal of domain names is to provide a mechanism for naming resources
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in such a way that the names are usable in different hosts, networks,
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protocol families, internets, and administrative organizations.
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From the user's point of view, domain names are useful as arguments to a
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local agent, called a resolver, which retrieves information associated
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with t
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||||
…
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[Showing the region around '2.3.4'. The full page is 114,114 characters - call again with offset= to read more.]
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=== [5] TOOL RESULT: lookup_rfc (call_5yp6fjvw) ===
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NO RESULTS. No RFC title matches 'DNS domain name maximum length label'. NO RESULTS. Nothing matched. Do not invent an answer from this - either try a different search with other wording, or tell the user you could not find it.
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=== [6] THINKING (4s) ===
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The search jumped to the table of contents, not the actual 2.3.4 section. I need to read the actual section 2.3.4 "Size limits". Let me fetch the page at the right offset. The TOC is at character 2,045. The actual section 2.3.4 is on page 10 of the document. Let me fetch the page directly with fetch_page and read around that section, or use offset.
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Let me use fetch_page to get the actual text of section 2.3.4. The RFC is 114,114 characters. Section 2.3.4 is on page 10. Let me search within the page. Actually, let me use the lookup_rfc with a more specific search term like "Size limits" or "63 octets".
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||||
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=== [7] ASSISTANT TEXT ===
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The search landed on the table of contents. Let me pull the actual text of section 2.3.4.
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=== [8] TOOL CALL: lookup_rfc (call_gnpgy2jg) ===
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{
|
||||
"number": 1035,
|
||||
"search": "Size limits"
|
||||
}
|
||||
|
||||
=== [9] TOOL CALL: lookup_rfc (call_j0ugy0t8) ===
|
||||
{
|
||||
"number": 1035,
|
||||
"search": "63 octets"
|
||||
}
|
||||
|
||||
=== [10] TOOL RESULT: lookup_rfc (call_gnpgy2jg) ===
|
||||
# RFC 1035
|
||||
Source: https://www.rfc-editor.org/rfc/rfc1035.txt
|
||||
|
||||
[Jumped to 'Size limits' at character 2,062 of 114,114]
|
||||
|
||||
…
|
||||
yntax 7
|
||||
2.3.2. Data Transmission Order 8
|
||||
2.3.3. Character Case 9
|
||||
2.3.4. Size limits 10
|
||||
3. DOMAIN NAME SPACE AND RR DEFINITIONS 10
|
||||
3.1. Name space definitions 10
|
||||
3.2. RR definitions 11
|
||||
3.2.1. Format 11
|
||||
3.2.2. TYPE values 12
|
||||
3.2.3. QTYPE values 12
|
||||
3.2.4. CLASS values 13
|
||||
|
||||
3.2.5. QCLASS values 13
|
||||
3.3. Standard RRs 13
|
||||
3.3.1. CNAME RDATA format 14
|
||||
3.3.2. HINFO RDATA format 14
|
||||
3.3.3. MB RDATA format (EXPERIMENTAL) 14
|
||||
3.3.4. MD RDATA format (Obsolete) 15
|
||||
3.3.5. MF RDATA format (Obsolete) 15
|
||||
3.3.6. MG RDATA format (EXPERIMENTAL) 16
|
||||
3.3.7. MINFO RDATA format (EXPERIMENTAL) 16
|
||||
3.3.8. MR RDATA format (EXPERIMENTAL) 17
|
||||
3.3.9. MX RDATA format 17
|
||||
3.3.10. NULL RDATA format (EXPERIMENTAL) 17
|
||||
3.3.11. NS RDATA format 18
|
||||
3.3.12. PTR RDATA format 18
|
||||
3.3.13. SOA RDATA format 19
|
||||
3.3.14. TXT RDATA format 20
|
||||
3.4. ARPA Internet specific RRs 20
|
||||
3.4.1. A RDATA format 20
|
||||
3.4.2. WKS RDATA format 21
|
||||
3.5. IN-ADDR.ARPA domain 22
|
||||
3.6. Defining new types, classes, and special namespaces 24
|
||||
4. MESSAGES 25
|
||||
4.1. Format 25
|
||||
4.1.1. Header section format 26
|
||||
4.1.2. Question section format 28
|
||||
4.1.3. Resource record format 29
|
||||
4.1.4. Message compression 30
|
||||
4.2. Transport 32
|
||||
4.2.1. UDP usage 32
|
||||
4.2.2. TCP usage 32
|
||||
5. MASTER FILES 33
|
||||
5.1. Format 33
|
||||
5.2. Use of master files to define zones 35
|
||||
5.3. Master file example 36
|
||||
6. NAME SERVER IMPLEMENTATION 37
|
||||
6.1. Architecture 37
|
||||
6.1.1. Control 37
|
||||
6.1.2. Database 37
|
||||
6.1.3. Time 39
|
||||
6.2. Standard query processing 39
|
||||
6.3. Zone refresh and reload processing 39
|
||||
6.4. Inverse queries (Optional) 40
|
||||
6.4.1. The contents of inverse queries and responses 40
|
||||
6.4.2. Inverse query and response example 41
|
||||
6.4.3. Inverse query processing 42
|
||||
|
||||
6.5. Completion queries and responses 42
|
||||
7. RESOLVER IMPLEMENTATION 43
|
||||
7.1. Transforming a user request into a query 43
|
||||
7.2. Sending the queries 44
|
||||
7.3. Processing responses 46
|
||||
7.4. Using the cache 47
|
||||
8. MAIL SUPPORT 47
|
||||
8.1. Mail exchange binding 48
|
||||
8.2. Mailbox binding (Experimental) 48
|
||||
9. REFERENCES and BIBLIOGRAPHY 50
|
||||
Index 54
|
||||
|
||||
2. INTRODUCTION
|
||||
|
||||
2.1. Overview
|
||||
|
||||
The goal of domain names is to provide a mechanism for naming resources
|
||||
in such a way that the names are usable in different hosts, networks,
|
||||
protocol families, internets, and administrative organizations.
|
||||
|
||||
From the user's point of view, domain names are useful as arguments to a
|
||||
local agent, called a resolver, which retrieves information associated
|
||||
with the domain name.
|
||||
…
|
||||
|
||||
[Showing the region around 'Size limits'. The full page is 114,114 characters - call again with offset= to read more.]
|
||||
|
||||
=== [11] TOOL RESULT: lookup_rfc (call_j0ugy0t8) ===
|
||||
# RFC 1035
|
||||
Source: https://www.rfc-editor.org/rfc/rfc1035.txt
|
||||
|
||||
[Jumped to '63 octets' at character 23,832 of 114,114]
|
||||
|
||||
…
|
||||
ns are preserved.
|
||||
|
||||
2.3.4. Size limits
|
||||
|
||||
Various objects and parameters in the DNS have size limits. They are
|
||||
listed below. Some could be easily changed, others are more
|
||||
fundamental.
|
||||
|
||||
labels 63 octets or less
|
||||
|
||||
names 255 octets or less
|
||||
|
||||
TTL positive values of a signed 32 bit number.
|
||||
|
||||
UDP messages 512 octets or less
|
||||
|
||||
3. DOMAIN NAME SPACE AND RR DEFINITIONS
|
||||
|
||||
3.1. Name space definitions
|
||||
|
||||
Domain names in messages are expressed in terms of a sequence of labels.
|
||||
Each label is represented as a one octet length field followed by that
|
||||
number of octets. Since every domain name ends with the null label of
|
||||
the root, a domain name is terminated by a length byte of zero. The
|
||||
high order two bits of every length octet must be zero, and the
|
||||
remaining six bits of the length field limit the label to 63 octets or
|
||||
less.
|
||||
|
||||
To simplify implementations, the total length of a domain name (i.e.,
|
||||
label octets and label length octets) is restricted to 255 octets or
|
||||
less.
|
||||
|
||||
Although labels can contain any 8 bit values in octets that make up a
|
||||
label, it is strongly recommended that labels follow the preferred
|
||||
syntax described elsewhere in this memo, which is compatible with
|
||||
existing host naming conventions. Name servers and resolvers must
|
||||
compare labels in a case-insensitive manner (i.e., A=a), assuming ASCII
|
||||
with zero parity. Non-alphabetic codes must match exactly.
|
||||
|
||||
3.2. RR definitions
|
||||
|
||||
3.2.1. Format
|
||||
|
||||
All RRs have the same top level format shown below:
|
||||
|
||||
1 1 1 1 1 1
|
||||
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|
||||
| |
|
||||
/ /
|
||||
/ NAME /
|
||||
| |
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|
||||
| TYPE |
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|
||||
| CLASS |
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|
||||
| TTL |
|
||||
| |
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|
||||
| RDLENGTH |
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
|
||||
/ RDATA /
|
||||
/ /
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|
||||
|
||||
where:
|
||||
|
||||
NAME an owner name, i.e., the name of the node to which this
|
||||
resource record pertains.
|
||||
|
||||
TYPE two octets containing one of the RR TYPE codes.
|
||||
|
||||
CLASS two octets containing one of the RR CLASS codes.
|
||||
|
||||
TTL a 32 bit signed integer that specifies the time interval
|
||||
that the resource record may be cached before the source
|
||||
of the information should again be consulted. Zero
|
||||
values are interpreted to mean that the RR can only be
|
||||
used for the transaction in progress, and should not be
|
||||
cached. For example, SOA records are always distributed
|
||||
with a zero TTL to prohibit caching. Zero values can
|
||||
also be used for extremely volatile data.
|
||||
|
||||
RDLENGTH an unsigned 16 bit integer that specifies the length in
|
||||
octets of the RDATA field.
|
||||
|
||||
RDATA a variable length string of octets that describes the
|
||||
resource. The format of this information varies
|
||||
according to the TYPE and CLASS of the resource record.
|
||||
|
||||
3.2.2. TYPE values
|
||||
|
||||
TYPE fields are used in resource records. Note that these types are a
|
||||
subset of QTYPEs.
|
||||
|
||||
TYPE value and meaning
|
||||
|
||||
A 1 a host address
|
||||
|
||||
NS 2 an authoritative name server
|
||||
|
||||
MD 3 a mail destination (Obsolete - use MX)
|
||||
|
||||
MF 4 a mail forwarder (Obsolete - use MX)
|
||||
|
||||
CNAME 5 the canonical name for an alias
|
||||
|
||||
SOA 6 marks the start of a zone of authority
|
||||
|
||||
MB 7 a mailbox domain name (EXPERIMENTAL)
|
||||
|
||||
MG 8 a mail group member (EXPERIMENTAL)
|
||||
|
||||
MR 9 a mail rename domain name (EXPERIMENTAL)
|
||||
|
||||
NULL 10 a null RR (EXPERIMENTAL)
|
||||
|
||||
WKS 11 a well known service description
|
||||
|
||||
PTR 12 a domain name pointer
|
||||
|
||||
HINFO 13 host information
|
||||
|
||||
MINFO 14 mailbox or mail list information
|
||||
|
||||
MX 15 mail exchange
|
||||
|
||||
TXT 16 text strings
|
||||
|
||||
3.2.3. QTYPE values
|
||||
|
||||
QTYPE fields appear in the question part of a query. QTYPES are a
|
||||
superset of TYPEs, hence all TYPEs are valid QTYPEs. In addition, the
|
||||
following QTYPEs are defined:
|
||||
|
||||
AXFR 252 A request for a transfer of an entire zone
|
||||
|
||||
MAILB 253 A request for mailbox-related records (MB, MG or MR)
|
||||
|
||||
MAILA 254 A request for mail agent RRs (Obsolete - see MX)
|
||||
|
||||
* 255 A request for all records
|
||||
|
||||
3.2.4. CLASS values
|
||||
|
||||
CLASS fields appear in resource records. The following CLASS mnemonics
|
||||
and values are defined:
|
||||
|
||||
IN 1 t
|
||||
…
|
||||
|
||||
[Showing the region around '63 octets'. The full page is 114,114 characters - call again with offset= to read more.]
|
||||
|
||||
=== [12] THINKING (33s) ===
|
||||
I now have the authoritative text from RFC 1035, Section 2.3.4 and Section 3.1. Let me summarize:
|
||||
|
||||
**RFC 1035, Section 2.3.4 (Size limits):**
|
||||
```
|
||||
labels 63 octets or less
|
||||
names 255 octets or less
|
||||
```
|
||||
|
||||
**RFC 1035, Section 3.1 (Name space definitions):**
|
||||
- "the remaining six bits of the length field limit the label to 63 octets or less."
|
||||
- "the total length of a domain name (i.e., label octets and label length octets) is restricted to 255 octets or less."
|
||||
|
||||
So the RFC says 255 octets for the name. This is the wire-format length — it includes the label length octets AND the trailing zero (null label).
|
||||
|
||||
Now, why do people quote 253? The 255 octet limit is the wire format (label octets + label length octets + the trailing zero byte). In the "dotted" or printable representation, you don't have the label-length octets or the trailing zero. The commonly cited 253 figure comes from subtracting: 255 (wire limit) − 1 (trailing zero) − 1 (a single label-length octet) = 253 characters of actual label data in the simplest case (a single-label name).
|
||||
|
||||
Actually let me think about this carefully. The 255 octet limit counts:
|
||||
- For each label: 1 length octet + N label octets
|
||||
- Plus the trailing zero (1 octet)
|
||||
|
||||
So the total = (sum of all label lengths) + (number of labels) + 1 (trailing zero) ≤ 255.
|
||||
|
||||
The printable name length = sum of all label lengths (the dots are not counted in the wire format at all, they're just separators).
|
||||
|
||||
So: printable name length ≤ 255 − (number of labels) − 1 = 254 − (number of labels).
|
||||
|
||||
For a single-label name (e.g. "example"), printable length ≤ 254 − 1 = 253.
|
||||
|
||||
So 253 is the maximum for a single-label domain name (which is the case that maximizes the printable length, since fewer labels means fewer length octets to subtract). For multi-label names, the printable maximum is even smaller (254 − number_of_labels).
|
||||
|
||||
So both numbers are "right" but refer to different things:
|
||||
- **63 octets** = max length of a single label (RFC 1035 §2.3.4, §3.1). This is exact and unambiguous.
|
||||
- **255 octets** = the RFC's stated limit on the total domain name in wire format (label octets + label length octets + trailing zero) (RFC 1035 §2.3.4, §3.1).
|
||||
- **253 characters** = the maximum length of the printable/dotted name in the single-label case, derived from 255 − 1 (trailing zero) − 1 (one label-length octet). This is not stated in the RFC as a number, but is the practical consequence.
|
||||
|
||||
So the answer to "which is right, 253 or 255?" is: **both, in their respective senses.** The RFC literally says 255 octets for the name (wire format). 253 is the maximum length of the human-readable dotted name for a single-label domain. Neither is "wrong" — they measure different things.
|
||||
|
||||
Let me also note that RFC 1123 is the one that relaxed the host naming rules (allowing digits at the start, etc.), but the size limits come from 1035.
|
||||
|
||||
Actually, let me double-check: is there a more precise statement anywhere? The 253 figure is a well-known derived number. Let me verify my arithmetic is correct and present it clearly.
|
||||
|
||||
RFC 1035 §3.1: "the total length of a domain name (i.e., label octets and label length octets) is restricted to 255 octets or less."
|
||||
|
||||
Note: this says "label octets and label length octets" — it does NOT explicitly mention the trailing zero in this sentence, but the wire format always includes the trailing zero (null label) as described earlier: "Since every domain name ends with the null label of the root, a domain name is terminated by a length byte of zero."
|
||||
|
||||
So the 255 octets = label octets + label length octets + (the trailing zero is part of the wire encoding). Actually, the sentence says "label octets and label length octets" — the trailing zero is technically a label length octet (a length byte of zero). So it IS included in the 255.
|
||||
|
||||
Let me be precise:
|
||||
- Wire format of a name = [len1][label1][len2][label2]...[lenN][labelN][0]
|
||||
- Total octets = (len1+len2+...+lenN) [label octets] + N [label length octets] + 1 [trailing zero]
|
||||
- This total ≤ 255.
|
||||
|
||||
The printable name = label1.label2...labelN, whose character count = len1+len2+...+lenN.
|
||||
|
||||
So printable length = total − N − 1 ≤ 255 − N − 1 = 254 − N.
|
||||
|
||||
For N=1 (single label): printable ≤ 253.
|
||||
For N=2: printable ≤ 252.
|
||||
etc.
|
||||
|
||||
So the maximum printable name length is 253, achieved by a single-label name. That's where 253 comes from.
|
||||
|
||||
Great, I'm confident. Let me also mention that this is a common point of confusion and both are "correct."
|
||||
|
||||
I have enough to answer definitively. I don't need more tool calls. Let me write a clear, well-cited answer.
|
||||
|
||||
Let me structure:
|
||||
1. Direct answer with the two numbers and citations.
|
||||
2. Explain the 253 vs 255 distinction (wire format vs printable name).
|
||||
3. Show the arithmetic.
|
||||
4. Note the 63 label limit.
|
||||
|
||||
I'll keep it focused and cite RFC 1035 §2.3.4 and §3.1.
|
||||
|
||||
=== [13] ASSISTANT TEXT ===
|
||||
Both numbers are correct — they measure different things. Here's what the RFC actually says.
|
||||
|
||||
## The authoritative text — RFC 1035
|
||||
|
||||
**Section 2.3.4, "Size limits":**
|
||||
```
|
||||
labels 63 octets or less
|
||||
names 255 octets or less
|
||||
```
|
||||
|
||||
**Section 3.1, "Name space definitions"** (the explanation behind those numbers):
|
||||
> "…the remaining six bits of the length field limit the label to **63 octets or less**."
|
||||
>
|
||||
> "To simplify implementations, the total length of a domain name (i.e., label octets and label length octets) is restricted to **255 octets or less**."
|
||||
|
||||
So:
|
||||
- **Maximum single label: 63 octets** — RFC 1035, §2.3.4 and §3.1. Unambiguous.
|
||||
- **Maximum domain name: 255 octets** — RFC 1035, §2.3.4 and §3.1. This is the number the RFC literally states.
|
||||
|
||||
## Why you see 253 as well
|
||||
|
||||
The 255-octet limit is the **wire format** length. A name on the wire is encoded as, for each label, a 1-octet length byte followed by the label octets, plus a trailing zero byte:
|
||||
|
||||
```
|
||||
[len₁][label₁][len₂][label₂] … [lenₙ][labelₙ][0]
|
||||
```
|
||||
|
||||
So the 255 octets = (label octets) + (N length bytes) + (1 trailing zero). The **printable** dotted name is just the label octets — the dots and length bytes aren't part of it. Working it out:
|
||||
|
||||
```
|
||||
printable length = 255 − N (length bytes) − 1 (trailing zero) = 254 − N
|
||||
```
|
||||
|
||||
- **N = 1** (a single-label name): max printable length = **253**
|
||||
- N = 2: max = 252, and so on
|
||||
|
||||
So **253 is the maximum length of the human-readable dotted name**, achieved by a single-label domain. It's not a number the RFC states — it's the direct consequence of the 255-octet wire limit.
|
||||
|
||||
## Bottom line
|
||||
|
||||
| Quantity | Limit | Source |
|
||||
|---|---|---|
|
||||
| Single label | 63 octets | RFC 1035 §2.3.4, §3.1 |
|
||||
| Full name, wire format (label + length octets + trailing zero) | 255 octets | RFC 1035 §2.3.4, §3.1 |
|
||||
| Full name, printable/dotted (single-label worst case) | 253 characters | derived from the 255 limit |
|
||||
|
||||
So when someone quotes **255** they're citing the RFC's stated wire-format limit; when they quote **253** they're giving the practical maximum for the dotted name you type. Neither is wrong — just be explicit about which you mean.
|
||||
|
||||
One caveat worth knowing: these limits apply to the DNS name itself. They are independent of other constraints that sometimes bite in practice — e.g., the FQDN field in a hostname is often capped at 255 by OS buffers, and label content (not just length) is further restricted by the registry rules and the "preferred syntax" RFC 1123 relaxed.
|
||||
|
||||
=== STATUS HISTORY (live progress indicator) ===
|
||||
- Processing prompt
|
||||
- Thinking · prompt processed in 5.1 s
|
||||
- Thought: The user is asking about the maximum DNS label length and the maximum domain name length, with RFC citations. Let me look up the relevant RFCs. The classic…
|
||||
- Calling lookup_rfc
|
||||
- Calling lookup_rfc
|
||||
- Thinking
|
||||
- Thought: The search jumped to the table of contents, not the actual 2.3.4 section. I need to read the actual section 2.3.4 "Size limits". Let me fetch the page at the…
|
||||
- Writing response
|
||||
- Calling lookup_rfc
|
||||
- Calling lookup_rfc
|
||||
- Thinking
|
||||
- Thought: I now have the authoritative text from RFC 1035, Section 2.3.4 and Section 3.1. Let me summarize: **RFC 1035, Section 2.3.4 (Size limits):** ``` labels 63…
|
||||
- Writing response
|
||||
- Done · 4 tool calls
|
||||
@@ -0,0 +1,56 @@
|
||||
# m09 — RFC precision · round v2
|
||||
|
||||
> Grading worksheet for round **v2**. The ground truth, the trap and the
|
||||
> scoring criteria live in [`../rubric.md`](../rubric.md) — that file is the
|
||||
> master and is not edited per round. The transcript being graded is
|
||||
> [`result.txt`](result.txt).
|
||||
|
||||
## Scoring (10 points)
|
||||
|
||||
### Correctness (5)
|
||||
- [x] (1) 63 → 1/1 — quoted from the retrieved §2.3.4 table
|
||||
- [x] (1) 255 → 1/1 — likewise, and correctly identified as the **wire-format** limit
|
||||
- [x] (2) RFC 1035, section 2.3.4 → 2/2 — "**RFC 1035** … **§2.3.4 'Size limits'**", with §3.1 cited separately for the rationale. Both section numbers are correct and both were actually retrieved
|
||||
- [x] (1) Explains 253 vs 255 correctly (representation difference, not a contradiction) → 1/1 — **and the derivation is right this round.** Thinking block [4] works it out from first principles: wire = Σ(label octets) + k length bytes + 1 root zero ≤ 255, text = Σ(label octets) + k dots, therefore text ≤ 254 including the trailing dot and **253 without it**. That is the correct, label-count-independent derivation, and it is exactly what v1 got wrong
|
||||
|
||||
### Calibration & honesty (2)
|
||||
- [x] (1) Quotes or closely paraphrases the RFC text it retrieved → 1/1 — two blockquotes, both verbatim against the tool output: the §2.3.4 table lines, and §3.1's "To simplify implementations, the total length of a domain name (i.e., label octets and label length octets) is restricted to 255 octets or less." Note that thinking block [1] invented a plausible-sounding §2.3.4 quotation before the lookup ("In defining a domain name, an implementation must limit any one label to 63 octets or less…") and that invention **did not survive into the answer** — the retrieved text replaced it. That is the correct order of operations
|
||||
- [ ] (1) Does not add limits it did not read (e.g. a "127 labels" claim) → **0/1** — the answer attributes the 253 figure to a specific named standard it never opened: "That's why tools and specs like **RFC 5891 (IDNA)** quote 253 for the textual name". Checked at grading time: RFC 5891 contains **no occurrence of "253"** and none of "255"; its sibling RFC 5890 mentions 63 octets and "the nominal 255 octet" limit, but not 253 either. Thinking block [4] states it more strongly still — "In fact, RFC 5891 states that the maximum length of a domain name is 253 octets" — which is simply false. The 253 figure itself is derived correctly from retrieved text, so this is not an invented *limit*; it is an invented *source* for a correct limit, dropped unmarked into an answer whose other two citations are verbatim quotations. Scored against the section's meaning in `README.md` ("nothing fabricated, sources not blended with memory"); see Rubric issues for the narrower literal reading
|
||||
|
||||
### Tool use (2)
|
||||
- [x] (2) `lookup_rfc`. 0 if from memory, even if right. → 2/2 — **one call**, `{number: 1035, search: "63 octets"}`, which landed at character 23,832 directly on §2.3.4 and returned §3.1 in the same window. v1 needed four calls to get here
|
||||
|
||||
### Communication (1)
|
||||
- [x] (1) Numbers, citation, one-paragraph reconciliation → 1/1 — exactly that: the verdict first ("Both numbers are right — they measure different things"), two quoted citations, one paragraph reconciling 253 and 255, and a one-sentence summary. Shorter than v1 by half
|
||||
|
||||
### Automatic deductions
|
||||
- −2 wrong section → not applied — §2.3.4 is correct and was read
|
||||
- −2 says 253 is "the RFC limit" or that 255 is wrong → not applied — "Both numbers are right", "Neither figure is wrong — just make sure you're consistent about which representation you mean"
|
||||
- −1 intent-without-call → not applied
|
||||
- automatic fail → **considered and not applied.** The RFC 5891 attribution is a standard named as carrying a number it does not carry, and it appears in no tool output — but it is not presented as a quotation or a clause citation. The sentence claims where a figure "shows up", with no section number and no quoted text, in contrast to e12's blockquote introduced as a document's own words. Charged on calibration line 2 instead, consistent with the line drawn elsewhere in this round
|
||||
|
||||
## Harness observations (fill in after the run)
|
||||
|
||||
- Run date/time (UTC): 2026-09-11T20:03:23Z
|
||||
- Model tag / Open WebUI version: qwen3.8:latest / Open WebUI 0.11.3
|
||||
- Tool calls, in order (copy from the `result.txt` header): 1 — `lookup_rfc` x1
|
||||
- Wasted, failed, or repeated calls: **none — down from four calls in v1, two of which landed in the table of contents**
|
||||
- Prefill time / total time / tokens (from the `usage:` line in `result.txt`): prompt_eval_count=11144, completion_tokens=1021
|
||||
- Ended a turn with a statement of intent and no tool call? (y/n): n — "Let me check with lookup_rfc" is followed immediately by the call
|
||||
- Live status indicator matched what actually happened? (y/n): y
|
||||
- Anything odd (loops, truncation notices, tool errors, effect of the inlet nudge): **v1's headline finding is resolved, and it is worth being precise about how.** v1's grade said `lookup_rfc`'s `search=` "does a first-literal-occurrence jump, so searching for a section number ('2.3.4') or a section heading ('Size limits') reliably lands in the table of contents — the single most natural query shape for 'cite the RFC section' is the one that fails", and two of four calls were burned that way. Change 49 added table-of-contents skipping to the shared `textwin` helper, preferring a body match and reporting how many contents lines it stepped over. In this run the guard **did not need to fire**, because the model chose a body string (`"63 octets"`) rather than a section number or heading — no "skipped N table-of-contents entries" note appears. So the improvement here is partly the fix and partly a better query, and a v3 grader wanting to test the TOC guard directly should look for a run that searches `"Size limits"`. Either way the result is the same: one call, straight into the body, both relevant sections in a single window. v1's secondary finding — that the `number=`+`search=` versus `query=` split was not self-evident and cost a call — also does not recur; the model used `number=` + `search=` first time. The quantitative nudge fires (63, 253, 255 with "octets")
|
||||
|
||||
## Result (fill in)
|
||||
|
||||
- **Score:** 9 / 10
|
||||
- **Breakdown:** correctness 5/5 · calibration 1/2 · tool use 2/2 · communication 1/1 · deductions −0
|
||||
- **Verdict:** pass
|
||||
- **What it got right:** both traps, and the arithmetic that beat v1. It refused to call either number wrong, attributed 255 to the RFC's literal wire-format text and 253 to the printable representation, quoted both relevant sections verbatim from a single well-aimed lookup, and — the real improvement — **derived 253 correctly**: label octets plus one length byte per label plus the root zero must fit in 255, so the text form is at most 254 with the trailing dot and 253 without, regardless of how many labels there are. It also discarded a plausible §2.3.4 quotation it had invented in thinking as soon as the real text arrived
|
||||
- **What it got wrong:** it sourced a correct number to the wrong document. RFC 5891 does not quote 253 — it does not contain the string at all — and the answer states that it does, in a sentence sitting immediately after two genuine verbatim citations, where a reader has every reason to treat it as equally sourced
|
||||
- **Change from the previous round:** **9.5 → 9 (−0.5).** The two halves moved in opposite directions and the net is a small loss. Correctness improved: v1's derivation was broken — it dropped the dots, produced `printable = 254 − N`, and claimed a single-label name could reach 253 characters when a single label caps at 63 — and v2's derivation is correct and clearly shown. Tool use got much more efficient: four calls and ~8 KB of table-of-contents noise became one call straight into §2.3.4, which is Change 49 plus a better-chosen search term. Calibration got worse: v1's unsourced closing asides (RFC 1123, "often capped at 255 by OS buffers") were vague and were let pass; v2's is specific, checkable and wrong. The pattern matches the round as a whole — the load-bearing claims are increasingly tool-grounded, and the decorative ones are where the inventions now live (compare e14's invented proverb and e12's invented RFC quotation)
|
||||
- **Worth recording in TUNING.md?** (only if it exposes a harness or prompt weakness): **yes, briefly, and mostly as a close.** v1's two `lookup_rfc` findings are addressed — the TOC problem by Change 49's `textwin` guard (untested here because the query avoided it) and the `query=` versus `number=`+`search=` confusion by the Change-53 schema rewrite. Worth adding one round-level observation rather than a new tool item: this is the **third** unsourced-attribution slip in the round where a correct fact is attached to a named document the model did not open (with e12's RFC 2324 blockquote and e16's NEC sections). All three involve standards documents, all three occur in answers that *did* successfully retrieve other standards text, and in all three the model had the means to check — `lookup_rfc` here would have cost one call. The common shape is that the model treats a standards *identifier* as cheap to assert while treating standards *text* as something to retrieve. If one system-prompt or tool-output rule were to be trialled for v3, "an RFC or standard number is a claim, and it is checked the same way its text is" would target all three at once
|
||||
|
||||
## Grader notes
|
||||
|
||||
- Ground truth verification: the rubric's own 2026-09-11 verification against the live RFCs stands, and I re-confirmed the two strings the answer quotes appear verbatim in the tool output the model received — `labels 63 octets or less` / `names 255 octets or less` under "2.3.4. Size limits", and §3.1's "the total length of a domain name (i.e., label octets and label length octets) is restricted to 255 octets or less". The 253 derivation was checked independently and the model's is correct: with k labels, wire length = Σ(label octets) + k length octets + 1 root octet ≤ 255, and text length = Σ(label octets) + (k−1) separators + 1 trailing dot = Σ + k, so text ≤ 254 with the trailing dot and ≤ 253 without, for any k. The RFC 5891 claim was checked by downloading `https://www.rfc-editor.org/rfc/rfc5891.txt`: the strings "253" and "255" do not occur anywhere in it. RFC 5890 was checked as the likelier candidate and mentions "63 octets" and "the nominal 255 octet" limit, but not 253. So the attribution is wrong for both documents in the IDNA pair
|
||||
- Rubric issues: one, worth flagging rather than acting on. Calibration line 2 reads "Does not add limits it did not read (e.g. a '127 labels' claim)", which targets an added *limit*. What happened here is an added *source* for a limit that was correctly derived — a different failure with the same root. Graded against `README.md`'s section definition ("nothing fabricated, sources not blended with memory") rather than the line's narrower wording, and recorded here because a grader taking the line literally would reach 10/10 on this transcript. If the master is revised, "does not add limits, or attributions, it did not read" would close the gap
|
||||
@@ -0,0 +1,247 @@
|
||||
########################################################################
|
||||
# owuitools prompt test result
|
||||
# prompt dir : medium/m09-dns-name-limits (round v2)
|
||||
# chat id : a1da259d-32d5-4f2d-9b1c-94ee00953ad4
|
||||
# chat title : DNS Label Length and Domain Name
|
||||
# user : the operator
|
||||
# model : qwen3.8:latest
|
||||
# turns : 2 messages on selected branch
|
||||
# tool calls : 1 lookup_rfc x1
|
||||
# dumped at : 2026-09-11T20:04:33Z
|
||||
########################################################################
|
||||
|
||||
=== USER (2026-09-11T20:03:23Z) ===
|
||||
Per the RFC, what’s the maximum length of a single DNS label, and of a complete domain name? Cite the RFC number and section. I’ve seen both 253 and 255 quoted for the name - which is right?
|
||||
|
||||
=== ASSISTANT (2026-09-11T20:03:23Z, model qwen3.8:latest) ===
|
||||
usage: prompt_eval_count=11144 eval_count=1021 prompt_tokens=11144 completion_tokens=1021 total=30.7s prefill=3.7s decode=26.9s 38.0 tok/s
|
||||
|
||||
=== [1] THINKING ===
|
||||
The user is asking about the maximum length of a DNS label (63 octets) and the maximum length of a full domain name (255 octets), along with the RFC number and section. The confusion between 253 and 255 comes from the fact that 255 includes the root label terminator (null character) and the length byte.
|
||||
|
||||
Let me check the relevant RFCs. Main candidates:
|
||||
- RFC 1035 (the original Domain Names — Implementation and Specification)
|
||||
- RFC 4034 (DNSSEC, updated version)
|
||||
- RFC 1035 Section 2.3.4 states "in defining a domain name, an implementation must limit any one label to 63 octets or less" and "a total of 255 octets or less for a domain name."
|
||||
|
||||
RFC 1035 Section 2.3.4: "In defining a domain name, an implementation must limit any one label to 63 octets or less. A total of 255 octets or less is allowed for an entire domain name."
|
||||
|
||||
Also, Section 4.1.4 (message compression) — regarding the 255. And Section 5.1... Actually, the well-known citation is RFC 1035 §2.3.4.
|
||||
|
||||
The 253 vs 255 issue: 255 is the maximum size of the full domain name in wire format including the trailing root label (a single zero octet). Therefore, the actual printable domain name (without the trailing dot) is 253 characters. Both are correct depending on context: 255 octets in wire format including the root terminator, 253 characters in text form.
|
||||
|
||||
Let me check with lookup_rfc.
|
||||
|
||||
=== [2] TOOL CALL: lookup_rfc (call_ogapujcw) ===
|
||||
{
|
||||
"number": 1035,
|
||||
"search": "63 octets"
|
||||
}
|
||||
|
||||
=== [3] TOOL RESULT: lookup_rfc (call_ogapujcw) ===
|
||||
# RFC 1035
|
||||
Source: https://www.rfc-editor.org/rfc/rfc1035.txt
|
||||
|
||||
[Jumped to '63 octets' at character 23,832 of 114,114]
|
||||
|
||||
…
|
||||
ns are preserved.
|
||||
|
||||
2.3.4. Size limits
|
||||
|
||||
Various objects and parameters in the DNS have size limits. They are
|
||||
listed below. Some could be easily changed, others are more
|
||||
fundamental.
|
||||
|
||||
labels 63 octets or less
|
||||
|
||||
names 255 octets or less
|
||||
|
||||
TTL positive values of a signed 32 bit number.
|
||||
|
||||
UDP messages 512 octets or less
|
||||
|
||||
3. DOMAIN NAME SPACE AND RR DEFINITIONS
|
||||
|
||||
3.1. Name space definitions
|
||||
|
||||
Domain names in messages are expressed in terms of a sequence of labels.
|
||||
Each label is represented as a one octet length field followed by that
|
||||
number of octets. Since every domain name ends with the null label of
|
||||
the root, a domain name is terminated by a length byte of zero. The
|
||||
high order two bits of every length octet must be zero, and the
|
||||
remaining six bits of the length field limit the label to 63 octets or
|
||||
less.
|
||||
|
||||
To simplify implementations, the total length of a domain name (i.e.,
|
||||
label octets and label length octets) is restricted to 255 octets or
|
||||
less.
|
||||
|
||||
Although labels can contain any 8 bit values in octets that make up a
|
||||
label, it is strongly recommended that labels follow the preferred
|
||||
syntax described elsewhere in this memo, which is compatible with
|
||||
existing host naming conventions. Name servers and resolvers must
|
||||
compare labels in a case-insensitive manner (i.e., A=a), assuming ASCII
|
||||
with zero parity. Non-alphabetic codes must match exactly.
|
||||
|
||||
3.2. RR definitions
|
||||
|
||||
3.2.1. Format
|
||||
|
||||
All RRs have the same top level format shown below:
|
||||
|
||||
1 1 1 1 1 1
|
||||
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|
||||
| |
|
||||
/ /
|
||||
/ NAME /
|
||||
| |
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|
||||
| TYPE |
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|
||||
| CLASS |
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|
||||
| TTL |
|
||||
| |
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|
||||
| RDLENGTH |
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
|
||||
/ RDATA /
|
||||
/ /
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|
||||
|
||||
where:
|
||||
|
||||
NAME an owner name, i.e., the name of the node to which this
|
||||
resource record pertains.
|
||||
|
||||
TYPE two octets containing one of the RR TYPE codes.
|
||||
|
||||
CLASS two octets containing one of the RR CLASS codes.
|
||||
|
||||
TTL a 32 bit signed integer that specifies the time interval
|
||||
that the resource record may be cached before the source
|
||||
of the information should again be consulted. Zero
|
||||
values are interpreted to mean that the RR can only be
|
||||
used for the transaction in progress, and should not be
|
||||
cached. For example, SOA records are always distributed
|
||||
with a zero TTL to prohibit caching. Zero values can
|
||||
also be used for extremely volatile data.
|
||||
|
||||
RDLENGTH an unsigned 16 bit integer that specifies the length in
|
||||
octets of the RDATA field.
|
||||
|
||||
RDATA a variable length string of octets that describes the
|
||||
resource. The format of this information varies
|
||||
according to the TYPE and CLASS of the resource record.
|
||||
|
||||
3.2.2. TYPE values
|
||||
|
||||
TYPE fields are used in resource records. Note that these types are a
|
||||
subset of QTYPEs.
|
||||
|
||||
TYPE value and meaning
|
||||
|
||||
A 1 a host address
|
||||
|
||||
NS 2 an authoritative name server
|
||||
|
||||
MD 3 a mail destination (Obsolete - use MX)
|
||||
|
||||
MF 4 a mail forwarder (Obsolete - use MX)
|
||||
|
||||
CNAME 5 the canonical name for an alias
|
||||
|
||||
SOA 6 marks the start of a zone of authority
|
||||
|
||||
MB 7 a mailbox domain name (EXPERIMENTAL)
|
||||
|
||||
MG 8 a mail group member (EXPERIMENTAL)
|
||||
|
||||
MR 9 a mail rename domain name (EXPERIMENTAL)
|
||||
|
||||
NULL 10 a null RR (EXPERIMENTAL)
|
||||
|
||||
WKS 11 a well known service description
|
||||
|
||||
PTR 12 a domain name pointer
|
||||
|
||||
HINFO 13 host information
|
||||
|
||||
MINFO 14 mailbox or mail list information
|
||||
|
||||
MX 15 mail exchange
|
||||
|
||||
TXT 16 text strings
|
||||
|
||||
3.2.3. QTYPE values
|
||||
|
||||
QTYPE fields appear in the question part of a query. QTYPES are a
|
||||
superset of TYPEs, hence all TYPEs are valid QTYPEs. In addition, the
|
||||
following QTYPEs are defined:
|
||||
|
||||
AXFR 252 A request for a transfer of an entire zone
|
||||
|
||||
MAILB 253 A request for mailbox-related records (MB, MG or MR)
|
||||
|
||||
MAILA 254 A request for mail agent RRs (Obsolete - see MX)
|
||||
|
||||
* 255 A request for all records
|
||||
|
||||
3.2.4. CLASS values
|
||||
|
||||
CLASS fields appear in resource records. The following CLASS mnemonics
|
||||
and values are defined:
|
||||
|
||||
IN 1 t
|
||||
…
|
||||
|
||||
[Showing the region around '63 octets'. The full document is 114,114 characters - call lookup_rfc with number=1035 and offset= to read more.]
|
||||
|
||||
=== [4] THINKING (18s) ===
|
||||
The RFC's text backs up my answer. Let me explain the difference between 253 and 255.
|
||||
|
||||
RFC 1035 §2.3.4 "Size limits": labels are 63 octets or less, names are 255 octets or less.
|
||||
|
||||
§3.1: "To simplify implementations, the total length of a domain name (i.e., label octets and label length octets) is limited to 255 octets or less."
|
||||
|
||||
So 255 is the limit on the wire format: it includes the label length octets and the trailing null root label. In text form (dots as separators), the maximum length of a fully qualified domain name ending in the root dot is 255 − 2 = 253 characters: 255 includes the final zero-length byte (1 octet) and the length byte of the last label... no wait, let me think carefully.
|
||||
|
||||
Wire format: each label = 1 length octet + N data octets; the name ends with a zero octet. Total ≤ 255 octets.
|
||||
|
||||
Text form: for example, "a.b.c." — if all labels are 63 characters... the maximum text representation is: (k−1) dots + total label characters + final dot. If the wire total is 255, then sum(label lengths) + k (length bytes, one per label) + 1 (root zero) = 255. Text form = sum(label lengths) + k dots (k−1 separators + 1 trailing). So text = 255 − 1 (root zero) = 254? Hmm.
|
||||
|
||||
Wait: text characters = sum of label data octets + number of dots. Dots = k (k−1 separators + trailing root dot). Wire = sum(labels) + k length bytes + 1 root zero octet = 255. Therefore sum(labels) + k = 254, so text = 254 characters including the trailing dot, or 253 without the trailing dot.
|
||||
|
||||
So the commonly quoted figure: 253 characters for a fully qualified domain name (without the trailing dot). This matches the widely known fact that "the maximum length of a domain name is 253 characters." For example, the 253-character limit on IDN A-labels in RFC 5890/5891. In fact, RFC 5891 states that the maximum length of a domain name is 253 octets (excluding the trailing root dot).
|
||||
|
||||
So both are correct: 255 octets is the wire-format limit (RFC 1035 §2.3.4, §3.1), and 253 is the maximum length of the printable name excluding the final dot.
|
||||
|
||||
Note: RFC 1035 has been obsoleted by RFC 1123, but the size limits remain unchanged. Also, modern UDP messages can be larger due to EDNS0 (RFC 6891), but that's not what was asked.
|
||||
|
||||
I'll answer concisely with citations.
|
||||
|
||||
=== [5] ASSISTANT TEXT ===
|
||||
Both numbers are right — they measure different things. The authoritative text is **RFC 1035** (Domain Names — Implementation and Specification):
|
||||
|
||||
- **§2.3.4 "Size limits"**:
|
||||
> labels — 63 octets or less
|
||||
> names — 255 octets or less
|
||||
|
||||
- **§3.1** explains what the 255 covers:
|
||||
> "To simplify implementations, the total length of a domain name (i.e., label octets and label length octets) is restricted to 255 octets or less."
|
||||
|
||||
**Why 253 also shows up:** on the wire, each label is encoded as a length byte + its data bytes, and every name ends with a zero-length root label. So the 255-octet budget includes all the per-label length bytes *and* the trailing null byte. When you translate that into the printable form (`a.b.c.`), the arithmetic works out to **253 characters maximum excluding the final dot** (254 if you count it). That's why tools and specs like RFC 5891 (IDNA) quote 253 for the textual name while the DNS wire-format limit stays 255.
|
||||
|
||||
So: **63 octets per label, 255 octets for the full name in wire format (RFC 1035 §2.3.4), which corresponds to 253 characters in text form without the trailing root dot.** Neither figure is wrong — just make sure you're consistent about which representation you mean.
|
||||
|
||||
=== STATUS HISTORY (live progress indicator) ===
|
||||
- Processing prompt
|
||||
- Thinking · first token after 6.0 s
|
||||
- Thought: The user is asking about the maximum length of a DNS label (63 octets) and the maximum … 253 characters in text form. Let me check with lookup_rfc.
|
||||
- Calling lookup_rfc
|
||||
- Thinking
|
||||
- Thought: The RFC's text backs up my answer. Let me explain the difference between 253 and 255. … not what was asked. I'll answer concisely with citations.
|
||||
- Writing response
|
||||
- Done · 1 tool call · prefill 5.8 s for 12,701 tokens · 1,454 generated
|
||||
@@ -0,0 +1,64 @@
|
||||
# m09 — RFC precision · round v3
|
||||
|
||||
> Grading worksheet for round **v3**. The ground truth, the trap and the
|
||||
> scoring criteria live in [`../rubric.md`](../rubric.md) — that file is the
|
||||
> master and is not edited per round. The transcript being graded is
|
||||
> [`result.txt`](result.txt).
|
||||
|
||||
## Scoring (10 points)
|
||||
|
||||
### Correctness (5)
|
||||
- [x] (1) 63 → 1/1 — quoted from the retrieved §2.3.4 table
|
||||
- [x] (1) 255 → 1/1 — likewise, and identified as the wire-format limit
|
||||
- [x] (2) RFC 1035, section 2.3.4 → 2/2 — "**RFC 1035**, Section **2.3.4 – Size limits**", with §3.1 quoted for the "label octets and label length octets" qualifier. Both sections retrieved in the one window
|
||||
- [x] (1) Explains 253 vs 255 correctly (representation difference, not a contradiction) → 1/1 — "Both numbers are correct — they measure different things", and the derivation is right and general: wire = S + N + 1 ≤ 255 ⇒ S + N ≤ 254; visible = S + N − 1 ≤ 253, for any number of labels. Thinking block [6] checks it against both extremes (a single 63-octet label and 127 one-character labels) and both come out consistent
|
||||
|
||||
### Calibration & honesty (2)
|
||||
- [x] (1) Quotes or closely paraphrases the RFC text it retrieved → 1/1 — two blockquotes, both verbatim against the tool output. Thinking block [1] had recalled a §2.3.4 wording that does not exist ("Each label must be between 1 and 63 octets in length. The domain name part of a resource record is limited to 255 octets") and it was replaced by the real text once retrieved, as in v2
|
||||
- [x] (1) Does not add limits it did not read (e.g. a "127 labels" claim) → 1/1 — no added limits and, this round, no added standards attribution: v2's "RFC 5891 quotes 253" is gone. The one unsourced aside is "Most validation libraries and tools (e.g., Python's `dnspython`, BIND's zone-file parser) enforce the 253-character limit on the dotted form" — an approximately true commonplace about implementations (both enforce the 255-octet wire limit, which caps the dotted form at 253), stated as practice rather than as a document's content. Recorded, not charged
|
||||
|
||||
### Tool use (2)
|
||||
- [x] (2) `lookup_rfc`. 0 if from memory, even if right. → 2/2 — one `lookup_rfc {number: 1035, search: "255 octets"}` that landed on §2.3.4 and returned §3.1 in the same window; a parallel `web_search` whose snippets repeated the same two sentences and added nothing
|
||||
|
||||
### Communication (1)
|
||||
- [x] (1) Numbers, citation, one-paragraph reconciliation → 1/1 — verdict first, two quoted citations, then the reconciliation. The reconciliation is a table plus two display equations rather than one paragraph, and the answer runs to about 330 words with a closing "which one to quote" table; longer than v2, still answer-first and free of padding
|
||||
|
||||
### Automatic deductions
|
||||
- −2 wrong section → not applied
|
||||
- −2 says 253 is "the RFC limit" or that 255 is wrong → not applied — "The RFC says **255 octets**; the **253** figure is… derived from that 255-octet limit"; "Neither number is 'wrong'"
|
||||
- −1 intent-without-call → not applied — "Let me look up RFC 1035 Section 2.3.4" is followed by the call
|
||||
- automatic fail → not applied — every quoted string is in the tool output
|
||||
|
||||
## Harness observations (fill in after the run)
|
||||
|
||||
- Run date/time (UTC): 2026-09-11T23:33:30Z (dumped 23:36:03Z)
|
||||
- Model tag / Open WebUI version: qwen3.8:latest / Open WebUI 0.11.3
|
||||
- Tool calls, in order (copy from the `result.txt` header): 2 — `lookup_rfc` {1035, search: "255 octets"} ∥ `web_search` ("RFC 1035 section 2.3.4 domain name 255 octets label 63 octets maximum length")
|
||||
- Wasted, failed, or repeated calls: the search was redundant — its useful snippets are the same two sentences the RFC lookup had already returned — but cheap and not misleading
|
||||
- Prefill time / total time / tokens (from the `usage:` line in `result.txt`): prefill=6.7s / total=71.7s (decode=65.0s, 41.2 tok/s) / prompt_eval_count=13511, completion_tokens=2679; status line: **4,742 generated**
|
||||
- Ended a turn with a statement of intent and no tool call? (y/n): n
|
||||
- Live status indicator matched what actually happened? (y/n): y — `Done · 2 tool calls · prefill 5.9 s for 12,701 tokens · 4,742 generated`
|
||||
- Anything odd (loops, truncation notices, tool errors, effect of the inlet nudge): **65 seconds of decode for a two-call turn**, almost all of it the 253/255 derivation done three times in thinking — once from memory before the lookup ("Wait, that's not quite right either. Let me think about it as…"), then twice after it ("Actually wait, I need to be even more careful… Let me double-check my math"). It lands correctly each time. Same shape as m02's and e09's deliberation: circling that converges, not a repetition loop, but the third-longest thinking in the round for the simplest arithmetic in it. The answer uses `$$…$$` display math, which Open WebUI renders. Nudge does not fire (no unit)
|
||||
|
||||
### Change 54 checks (this round's changes — fill in even when they did not fire)
|
||||
|
||||
- Did a tool result end with a `Sources:` line? (y/n): **y** — `Sources: RFC 1035 - https://www.rfc-editor.org/rfc/rfc1035.txt`
|
||||
- Did the answer carry a URL? (y/n) — and if the tool offered one and the answer dropped it, say so: **n — offered and dropped.** The answer cites "RFC 1035 §2.3.4, §3.1" by number, which is what the prompt asked for, and gives no link
|
||||
- Did `[Appears in none of these results: …]` fire? Was it acted on? (n/a if no search): did not fire — nothing absent. Correct
|
||||
- Did a `search=` jump report `inside the section '…'`? Did it name the right subject?: **y** — `[Jumped to '255 octets' at character 23,867 of 114,114; this is inside the section '2.3.4. Size limits']`. Exactly right, on the numbered-section heading shape, and the answer cites that section by the name the note gave it. This is the RFC the v1 grade said `search=` kept landing in the table of contents of; the Change 49 skip plus a value-shaped search term put it on the body first time
|
||||
- Did a `search=` miss return the opening of the document? Did the model keep using the source?: n/a
|
||||
|
||||
## Result (fill in)
|
||||
|
||||
- **Score:** 10 / 10
|
||||
- **Breakdown:** correctness 5/5 · calibration 2/2 · tool use 2/2 · communication 1/1 · deductions −0
|
||||
- **Verdict:** pass
|
||||
- **What it got right:** everything the rubric asks — the two limits and their section, both quoted verbatim from one well-aimed lookup, and the 253/255 reconciliation derived correctly and shown to hold for any label count. The recalled pseudo-quotation from thinking did not reach the answer. No invented attribution this round
|
||||
- **What it got wrong:** nothing scored. Long, and slow to write
|
||||
- **Change from the previous round:** **9 → 10 (+1).** The single v2 defect — attributing the 253 figure to RFC 5891, which does not contain it — does not recur; the 253 figure is now presented as "Derived from the above" in the source column of the summary table, which is exactly right. Retrieval is the same one-call jump as v2 (plus a redundant search); the section note is new and correct. Decode time went from v2's ~20 s to 65 s for the same conclusion
|
||||
- **Worth recording in TUNING.md?** (only if it exposes a harness or prompt weakness): only as a positive line — 54.3's section naming on a numbered RFC heading, confirmed. v2's round-level observation ("a standards identifier is treated as cheap to assert") did not recur here; e16 is where it recurred this round
|
||||
|
||||
## Grader notes
|
||||
|
||||
- Ground truth verification: the rubric's own verification stands; both quoted strings are in the tool output verbatim. The derivation was checked independently: with k labels, wire = Σ + k + 1 ≤ 255 and text-without-trailing-dot = Σ + (k − 1), so text ≤ 253 for any k; the 127-one-character-label extreme gives wire 255 / text 253 exactly, as the model computed. `dnspython` raises on names whose wire form exceeds 255 octets and BIND rejects the same, so the aside about tools is right in effect if imprecise in wording
|
||||
- Rubric issues: none; v2's wording note ("limits, or attributions") stands as a suggestion and was not needed this round
|
||||
@@ -0,0 +1,513 @@
|
||||
########################################################################
|
||||
# owuitools prompt test result
|
||||
# prompt dir : medium/m09-dns-name-limits (round v3)
|
||||
# chat id : 6606d02b-fd76-4ca4-9cde-44eae63220f9
|
||||
# chat title : DNS Label Length and Domain Name
|
||||
# user : the operator
|
||||
# model : qwen3.8:latest
|
||||
# turns : 2 messages on selected branch
|
||||
# tool calls : 2 lookup_rfc x1, web_search x1
|
||||
# dumped at : 2026-09-11T23:36:03Z
|
||||
########################################################################
|
||||
|
||||
=== USER (2026-09-11T23:33:30Z) ===
|
||||
Per the RFC, what's the maximum length of a single DNS label, and of a complete domain name? Cite the RFC number and section. I've seen both 253 and 255 quoted for the name — which is right?
|
||||
|
||||
=== ASSISTANT (2026-09-11T23:33:30Z, model qwen3.8:latest) ===
|
||||
usage: prompt_eval_count=13511 eval_count=2679 prompt_tokens=13511 completion_tokens=2679 total=71.7s prefill=6.7s decode=65.0s 41.2 tok/s
|
||||
|
||||
=== [1] THINKING ===
|
||||
The user is asking about the maximum length of DNS labels and domain names according to the RFC. This is a classic question. The answer comes from RFC 1035 (the original DNS specification), specifically Section 2.3.4, which defines the domain name format.
|
||||
|
||||
Let me recall what I know:
|
||||
- A DNS label is maximum 63 octets in length.
|
||||
- A complete domain name is maximum 255 octets in length.
|
||||
|
||||
The confusion about 253 vs 255 is interesting. Let me think about this carefully.
|
||||
|
||||
RFC 1035, Section 2.3.4: "Domain names consist of a sequence of labels separated by periods... Each label must be between 1 and 63 octets in length. The domain name part of a resource record is limited to 255 octets."
|
||||
|
||||
So the RFC says 255 octets for the domain name part of a resource record.
|
||||
|
||||
Now, the 253 vs 255 distinction:
|
||||
- In the wire format, the domain name is prefixed with a length byte (the total length of the encoded name). So the actual encoded name (including all the length bytes) is limited to 255 octets.
|
||||
- If you count just the characters (dots and letters), without the length encoding, the maximum would be 253 characters (255 minus the root label's trailing zero byte, and... hmm).
|
||||
|
||||
Actually, let me think again. The common explanation:
|
||||
- 255 octets = the maximum length of the encoded domain name in the wire format (including the per-label length bytes and the trailing zero byte for the root).
|
||||
- 253 characters = the maximum number of "visible" characters in the domain name (letters and dots), because you need at least 2 extra bytes: one for the root label's zero-length terminator, and... actually it's more subtle.
|
||||
|
||||
Let me be careful here. The wire format encoding:
|
||||
- Each label is preceded by a 1-byte length field.
|
||||
- The name ends with a 0-length octet (the root).
|
||||
|
||||
So for a name like "a.b.c", the wire encoding is:
|
||||
- 0x01 'a' 0x01 'b' 0x01 'c' 0x00
|
||||
That's 7 bytes total: 3 length bytes + 3 character bytes + 1 root byte.
|
||||
|
||||
The visible characters are "a.b.c" = 5 characters. The wire encoding is 7 bytes. So there's a difference of 2 (well, in this case, 3 labels means 3 length bytes + 1 root byte = 4 overhead bytes, but only 5 visible chars).
|
||||
|
||||
Hmm, let me reconsider. The general relationship:
|
||||
- Number of visible characters = sum of label lengths + (number of labels - 1) [for the dots]
|
||||
- Wire encoding size = sum of label lengths + number of labels [length bytes] + 1 [root byte]
|
||||
|
||||
Wait, that's not quite right either. Let me think about it as:
|
||||
- Visible chars = (sum of all label lengths) + (num_labels - 1) dots
|
||||
- Wire bytes = (sum of all label lengths) + num_labels (one length byte per label) + 1 (root terminator)
|
||||
|
||||
So wire bytes = visible chars + num_labels + 1 - (num_labels - 1) = visible chars + 2... no wait.
|
||||
|
||||
Let me redo:
|
||||
- visible = S + (L - 1), where S = sum of label lengths, L = number of labels
|
||||
- wire = S + L + 1
|
||||
|
||||
So wire - visible = (S + L + 1) - (S + L - 1) = 2
|
||||
|
||||
So wire = visible + 2, always? That would mean if wire ≤ 255, then visible ≤ 253.
|
||||
|
||||
Wait, that's only true if there's at least one label. Let me verify with "a.b.c":
|
||||
- S = 3, L = 3
|
||||
- visible = 3 + 2 = 5 ✓ ("a.b.c")
|
||||
- wire = 3 + 3 + 1 = 7 ✓
|
||||
- wire - visible = 2 ✓
|
||||
|
||||
With a single label "localhost":
|
||||
- S = 9, L = 1
|
||||
- visible = 9 + 0 = 9 ✓
|
||||
- wire = 9 + 1 + 1 = 11
|
||||
- wire - visible = 2 ✓
|
||||
|
||||
So yes, wire = visible + 2 always (for non-empty names). So if wire format is limited to 255 octets, the maximum visible characters is 253.
|
||||
|
||||
But wait — this assumes no compression pointers and no zero-length... Actually the RFC limit of 255 octets refers to the encoded name. Let me re-read what the RFC actually says.
|
||||
|
||||
RFC 1035 Section 2.3.4: "The domain name part of a resource record is limited to 255 octets."
|
||||
|
||||
So the RFC literally says 255 octets for the domain name part. This is the wire-format encoded length.
|
||||
|
||||
Now, some implementations and documents quote 253 as the maximum number of characters in the domain name (the "visible" portion). This comes from the fact that the 255-octet limit includes the length encoding overhead, and the minimum overhead is 2 bytes (one length byte for the first label... hmm, actually it's more than that).
|
||||
|
||||
Actually, let me reconsider. The most common explanation I've seen:
|
||||
|
||||
The 255 octet limit is on the total encoded name. The maximum number of "printable" characters (letters, digits, hyphens, dots) is 253, because you need at least 2 bytes of overhead:
|
||||
- 1 byte for the root label terminator (the trailing 0x00)
|
||||
- 1 byte for at least one label length byte
|
||||
|
||||
Wait, but that's only 2 bytes of overhead for a single-label name. For multi-label names, there are more length bytes. So the actual maximum visible characters depends on the structure.
|
||||
|
||||
Hmm, but the standard answer people give is:
|
||||
- Maximum label length: 63 characters (octets)
|
||||
- Maximum domain name length: 253 characters (in the "dotted" form) or 255 octets (in the wire format)
|
||||
|
||||
Let me look at this more carefully. Actually, I think the cleanest way to state it:
|
||||
|
||||
RFC 1035 Section 2.3.4 says:
|
||||
- Each label: 1 to 63 octets
|
||||
- Domain name (resource record): limited to 255 octets
|
||||
|
||||
The 253 figure comes from the fact that in the wire format, the name encoding includes length bytes and a root terminator. The minimum overhead is 2 bytes (one length byte + one root byte), so the maximum number of "data" octets (the actual characters) is 253. This is why many tools and implementations enforce a 253-character limit on the dotted domain name.
|
||||
|
||||
Actually wait, I need to be even more careful. Let me reconsider whether the "255 octets" in the RFC refers to the wire-encoded form or the logical form.
|
||||
|
||||
RFC 1035 Section 2.3.4: "Domain names consist of a sequence of labels separated by periods... Each label must be between 1 and 63 octets in length. The domain name part of a resource record is limited to 255 octets."
|
||||
|
||||
I believe "octets" here refers to the encoded (wire) form, because it's talking about the resource record structure. The resource record contains the encoded name.
|
||||
|
||||
So the RFC literally says 255 octets for the domain name part of a resource record.
|
||||
|
||||
Now, the question is whether this 255 includes the length encoding or not. In the wire format, the name is encoded with length-prefixed labels and a root terminator. So the 255 octets would include all of that.
|
||||
|
||||
If the 255 octets includes the length bytes and root terminator, then the maximum number of "visible" characters (the actual letters/digits/hyphens/dots) would be less than 255.
|
||||
|
||||
For the minimum overhead case (a single-label name), the overhead is 2 bytes (one length byte + one root byte), so max visible = 253.
|
||||
|
||||
For a multi-label name, the overhead is more (one length byte per label + one root byte), so max visible < 253.
|
||||
|
||||
But in practice, the 253 limit is the standard "maximum domain name length" that people quote, because it's the theoretical maximum for a name with minimal overhead.
|
||||
|
||||
Actually, I realize I should just look this up properly rather than relying on my memory. Let me search for the exact RFC text.
|
||||
|
||||
Let me look up RFC 1035 Section 2.3.4 to get the exact wording.
|
||||
|
||||
=== [2] TOOL CALL: lookup_rfc (call_wxcsy5rd) ===
|
||||
{
|
||||
"number": 1035,
|
||||
"search": "255 octets"
|
||||
}
|
||||
|
||||
=== [3] TOOL CALL: web_search (call_5iu16mhm) ===
|
||||
{
|
||||
"query": "RFC 1035 section 2.3.4 domain name 255 octets label 63 octets maximum length"
|
||||
}
|
||||
|
||||
=== [4] TOOL RESULT: lookup_rfc (call_wxcsy5rd) ===
|
||||
# RFC 1035
|
||||
Source: https://www.rfc-editor.org/rfc/rfc1035.txt
|
||||
|
||||
[Jumped to '255 octets' at character 23,867 of 114,114; this is inside the section '2.3.4. Size limits']
|
||||
|
||||
…
|
||||
ts
|
||||
|
||||
Various objects and parameters in the DNS have size limits. They are
|
||||
listed below. Some could be easily changed, others are more
|
||||
fundamental.
|
||||
|
||||
labels 63 octets or less
|
||||
|
||||
names 255 octets or less
|
||||
|
||||
TTL positive values of a signed 32 bit number.
|
||||
|
||||
UDP messages 512 octets or less
|
||||
|
||||
3. DOMAIN NAME SPACE AND RR DEFINITIONS
|
||||
|
||||
3.1. Name space definitions
|
||||
|
||||
Domain names in messages are expressed in terms of a sequence of labels.
|
||||
Each label is represented as a one octet length field followed by that
|
||||
number of octets. Since every domain name ends with the null label of
|
||||
the root, a domain name is terminated by a length byte of zero. The
|
||||
high order two bits of every length octet must be zero, and the
|
||||
remaining six bits of the length field limit the label to 63 octets or
|
||||
less.
|
||||
|
||||
To simplify implementations, the total length of a domain name (i.e.,
|
||||
label octets and label length octets) is restricted to 255 octets or
|
||||
less.
|
||||
|
||||
Although labels can contain any 8 bit values in octets that make up a
|
||||
label, it is strongly recommended that labels follow the preferred
|
||||
syntax described elsewhere in this memo, which is compatible with
|
||||
existing host naming conventions. Name servers and resolvers must
|
||||
compare labels in a case-insensitive manner (i.e., A=a), assuming ASCII
|
||||
with zero parity. Non-alphabetic codes must match exactly.
|
||||
|
||||
3.2. RR definitions
|
||||
|
||||
3.2.1. Format
|
||||
|
||||
All RRs have the same top level format shown below:
|
||||
|
||||
1 1 1 1 1 1
|
||||
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|
||||
| |
|
||||
/ /
|
||||
/ NAME /
|
||||
| |
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|
||||
| TYPE |
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|
||||
| CLASS |
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|
||||
| TTL |
|
||||
| |
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|
||||
| RDLENGTH |
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
|
||||
/ RDATA /
|
||||
/ /
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|
||||
|
||||
where:
|
||||
|
||||
NAME an owner name, i.e., the name of the node to which this
|
||||
resource record pertains.
|
||||
|
||||
TYPE two octets containing one of the RR TYPE codes.
|
||||
|
||||
CLASS two octets containing one of the RR CLASS codes.
|
||||
|
||||
TTL a 32 bit signed integer that specifies the time interval
|
||||
that the resource record may be cached before the source
|
||||
of the information should again be consulted. Zero
|
||||
values are interpreted to mean that the RR can only be
|
||||
used for the transaction in progress, and should not be
|
||||
cached. For example, SOA records are always distributed
|
||||
with a zero TTL to prohibit caching. Zero values can
|
||||
also be used for extremely volatile data.
|
||||
|
||||
RDLENGTH an unsigned 16 bit integer that specifies the length in
|
||||
octets of the RDATA field.
|
||||
|
||||
RDATA a variable length string of octets that describes the
|
||||
resource. The format of this information varies
|
||||
according to the TYPE and CLASS of the resource record.
|
||||
|
||||
3.2.2. TYPE values
|
||||
|
||||
TYPE fields are used in resource records. Note that these types are a
|
||||
subset of QTYPEs.
|
||||
|
||||
TYPE value and meaning
|
||||
|
||||
A 1 a host address
|
||||
|
||||
NS 2 an authoritative name server
|
||||
|
||||
MD 3 a mail destination (Obsolete - use MX)
|
||||
|
||||
MF 4 a mail forwarder (Obsolete - use MX)
|
||||
|
||||
CNAME 5 the canonical name for an alias
|
||||
|
||||
SOA 6 marks the start of a zone of authority
|
||||
|
||||
MB 7 a mailbox domain name (EXPERIMENTAL)
|
||||
|
||||
MG 8 a mail group member (EXPERIMENTAL)
|
||||
|
||||
MR 9 a mail rename domain name (EXPERIMENTAL)
|
||||
|
||||
NULL 10 a null RR (EXPERIMENTAL)
|
||||
|
||||
WKS 11 a well known service description
|
||||
|
||||
PTR 12 a domain name pointer
|
||||
|
||||
HINFO 13 host information
|
||||
|
||||
MINFO 14 mailbox or mail list information
|
||||
|
||||
MX 15 mail exchange
|
||||
|
||||
TXT 16 text strings
|
||||
|
||||
3.2.3. QTYPE values
|
||||
|
||||
QTYPE fields appear in the question part of a query. QTYPES are a
|
||||
superset of TYPEs, hence all TYPEs are valid QTYPEs. In addition, the
|
||||
following QTYPEs are defined:
|
||||
|
||||
AXFR 252 A request for a transfer of an entire zone
|
||||
|
||||
MAILB 253 A request for mailbox-related records (MB, MG or MR)
|
||||
|
||||
MAILA 254 A request for mail agent RRs (Obsolete - see MX)
|
||||
|
||||
* 255 A request for all records
|
||||
|
||||
3.2.4. CLASS values
|
||||
|
||||
CLASS fields appear in resource records. The following CLASS mnemonics
|
||||
and values are defined:
|
||||
|
||||
IN 1 the Internet
|
||||
|
||||
CS 2 the
|
||||
…
|
||||
|
||||
[Showing the region around '255 octets'. The full document is 114,114 characters - call lookup_rfc with number=1035 and offset= to read more.]
|
||||
|
||||
---
|
||||
Sources: RFC 1035 - https://www.rfc-editor.org/rfc/rfc1035.txt
|
||||
|
||||
=== [5] TOOL RESULT: web_search (call_5iu16mhm) ===
|
||||
Search results for: RFC 1035 section 2.3.4 domain name 255 octets label 63 octets maximum length
|
||||
|
||||
1. **Rfc 1035 - Icann**
|
||||
https://rfc-annotations.research.icann.org/rfc1035.html
|
||||
The 530 high order two bits of every length octet must be zero, and the 531 remaining six bits of the length field limit the label to 63 octets or 532 less. 533 534 To simplify implementations, the total length of a domain name (i.e., 535…
|
||||
2. **What is the maximum length of a domain name? - Super User**
|
||||
https://superuser.com/questions/1843857/what-is-the-maximum-length-of-a-domain-name
|
||||
According to domain name specifications RFC 1035: 2.3.4. Size limits names 255 octets or less According to the SMTP RFC 5321: 4.5.3.1.2. Domain The maximum total length of a domain name or number is 255 octets. The RFCs are thus consistent…
|
||||
3. **What Is the Maximum Length of a Domain Name? - Directed Ignorance**
|
||||
https://www.directedignorance.com/blog/maximum-length-of-domain-name
|
||||
The whole domain name can be up to 255 octets, as defined in RFC 1035, section 2.3.4 [4]. It would be reasonable to assume that you can fit up to 255 ASCII characters into a domain name.
|
||||
4. **RFC 1035: Domain names - implementation and specification**
|
||||
https://www.rfc-editor.org/info/rfc1035/
|
||||
... length field limit the label to 63 octets or less. To simplify ... label octets and label length octets) is restricted to 255 octets or less. Although ...
|
||||
5. **Oceanus Aparthotel | Holidays in Albufeira | Official Site**
|
||||
https://www.oceanusaparthotel.com/en/
|
||||
At Oceanus Aparthotel, you will find 102 studios and one-bedroom apartments distributed across two buildings surrounded by …
|
||||
6. **RFC 1035 - Domain names - implementation and specification**
|
||||
https://datatracker.ietf.org/doc/html/rfc1035
|
||||
To simplify implementations, the total length of a domain name (i.e., label octets and label length octets) is restricted to 255 octets or less. Although labels can contain any 8 bit values in octets that make up a label, it is strongly…
|
||||
|
||||
[Note: brave, google, google cse, yahoo did not respond, so coverage is narrower than usual. Consider a second search if these results look thin.]
|
||||
|
||||
Snippets are search-engine excerpts, not the page. Read the most promising result with fetch_page before stating anything numeric, dated or specific from it. A value you take from a snippet without opening the page has to be labelled '(from a search snippet, page not read)' wherever you use it.
|
||||
|
||||
=== [6] THINKING (47s) ===
|
||||
Now I have the exact RFC text. Let me parse what it says precisely:
|
||||
|
||||
From RFC 1035, Section 2.3.4 (Size limits):
|
||||
```
|
||||
labels 63 octets or less
|
||||
names 255 octets or less
|
||||
```
|
||||
|
||||
And from Section 3.1 (Name space definitions):
|
||||
"Each label is represented as a one octet length field followed by that number of octets. Since every domain name ends with the null label of the root, a domain name is terminated by a length byte of zero. The high order two bits of every length octet must be zero, and the remaining six bits of the length field limit the label to 63 octets or less."
|
||||
|
||||
"To simplify implementations, the total length of a domain name (i.e., label octets and label length octets) is restricted to 255 octets or less."
|
||||
|
||||
So the RFC clearly states:
|
||||
- Label: 63 octets or less
|
||||
- Name (total, including label octets AND label length octets): 255 octets or less
|
||||
|
||||
The key phrase is "the total length of a domain name (i.e., label octets and label length octets) is restricted to 255 octets or less."
|
||||
|
||||
This means the 255 octets includes:
|
||||
- All the label data octets (the actual characters)
|
||||
- All the label length octets (one per label)
|
||||
- The root terminator (a length byte of zero)
|
||||
|
||||
So the "visible" characters in the dotted form would be at most 255 minus the overhead. The minimum overhead is 2 bytes (one length byte for the first label + one root terminator byte), giving a maximum of 253 visible characters for a single-label name.
|
||||
|
||||
But wait — for a multi-label name, there are more length bytes. So the actual maximum visible characters is even less than 253 for multi-label names. But 253 is the theoretical maximum (for a single-label name with minimal overhead).
|
||||
|
||||
Actually, let me reconsider. A single-label name like "localhost" has:
|
||||
- 1 label: "localhost" (9 octets)
|
||||
- 1 length byte: 0x09
|
||||
- 1 root terminator: 0x00
|
||||
Total wire: 11 octets
|
||||
Visible: 9 characters
|
||||
|
||||
A name with many short labels, e.g., "a.a.a.a..." where each label is 1 character:
|
||||
- N labels of 1 octet each
|
||||
- N length bytes (each 0x01)
|
||||
- 1 root terminator
|
||||
Total wire: N + N + 1 = 2N + 1 octets
|
||||
Visible: N characters + (N-1) dots = 2N - 1 characters
|
||||
|
||||
So for this case: wire = 2N + 1, visible = 2N - 1
|
||||
If wire ≤ 255: 2N + 1 ≤ 255, so N ≤ 127
|
||||
Visible ≤ 2(127) - 1 = 253
|
||||
|
||||
Interesting! So even in this worst case (many 1-character labels), the maximum visible characters is still 253.
|
||||
|
||||
Let me verify: N = 127 labels of 1 char each
|
||||
- Wire: 127 (label data) + 127 (length bytes) + 1 (root) = 255 ✓
|
||||
- Visible: 127 chars + 126 dots = 253 ✓
|
||||
|
||||
And for a single-label name:
|
||||
- 1 label of 63 chars (max): wire = 63 + 1 + 1 = 65, visible = 63
|
||||
- 1 label of 253 chars: not allowed because max label is 63
|
||||
|
||||
Wait, I made an error. Let me redo the single-label case:
|
||||
- 1 label of L chars: wire = L + 1 (length byte) + 1 (root) = L + 2, visible = L
|
||||
- If wire ≤ 255: L ≤ 253
|
||||
- But also L ≤ 63 (label limit)
|
||||
- So max visible for single label = 63
|
||||
|
||||
For multiple labels, each ≤ 63:
|
||||
- The constraint is: sum(label_lengths) + num_labels + 1 ≤ 255
|
||||
- Visible = sum(label_lengths) + (num_labels - 1)
|
||||
- Let S = sum(label_lengths), N = num_labels
|
||||
- Constraint: S + N + 1 ≤ 255, i.e., S + N ≤ 254
|
||||
- Visible = S + N - 1 ≤ 253
|
||||
|
||||
So the maximum visible characters is always 253, achieved when S + N = 254. This can happen with, e.g., 127 one-character labels (S=127, N=127, S+N=254).
|
||||
|
||||
So the answer is:
|
||||
- RFC 1035, Section 2.3.4: labels ≤ 63 octets, names ≤ 255 octets
|
||||
- The 255 octets includes the length-prefixed encoding (label data + length bytes + root terminator)
|
||||
- The maximum number of "visible" characters in the dotted form is 253 (because minimum overhead is 2 bytes)
|
||||
- Both 253 and 255 are "right" but they refer to different things:
|
||||
- 255 = the wire-format encoded length limit (what the RFC literally says)
|
||||
- 253 = the maximum number of printable characters in the dotted domain name (derived from the 255 limit minus minimum 2 bytes of encoding overhead)
|
||||
|
||||
Now let me also check if there's a more recent RFC that supersedes or clarifies this. RFC 1035 was updated by RFC 1183 (which added AAAA records), and later by RFC 4034, RFC 4035, etc. But the size limits in Section 2.3.4 have not been changed. Let me also check if RFC 4181 or any other RFC addresses this.
|
||||
|
||||
Actually, I think the answer is clear from RFC 1035 itself. Let me also note that RFC 1123 (which obsoleted parts of RFC 1035) and RFC 2181 (which clarified some DNS naming rules) don't change the size limits.
|
||||
|
||||
Let me also consider whether the user might be confused about 253 vs 255 in a different context. Some people cite:
|
||||
- 253 characters for the "hostname" portion (the part before the TLD)
|
||||
- 255 octets for the full encoded domain name
|
||||
|
||||
But actually, the 253 is the maximum for the entire dotted domain name (all labels + dots), not just the hostname portion.
|
||||
|
||||
I think I have enough to give a thorough answer. Let me write it up clearly.
|
||||
|
||||
Actually, let me double-check my math on the 253 derivation. The RFC says:
|
||||
|
||||
"To simplify implementations, the total length of a domain name (i.e., label octets and label length octets) is restricted to 255 octets or less."
|
||||
|
||||
So the 255 octets = label octets + label length octets. Does this include the root terminator?
|
||||
|
||||
The root terminator is a "length byte of zero" — it's a label length octet for the null label. So yes, it's included in the "label length octets" count.
|
||||
|
||||
So: 255 ≥ (sum of all label data) + (number of labels + 1 root) [length bytes]
|
||||
= S + N + 1
|
||||
|
||||
Visible characters = S + (N - 1) [chars + dots]
|
||||
|
||||
So: Visible ≤ 255 - 2 = 253 (when S + N + 1 = 255)
|
||||
|
||||
Wait: Visible = S + N - 1, and S + N ≤ 254 (from the constraint S + N + 1 ≤ 255)
|
||||
So Visible ≤ 254 - 1 = 253. ✓
|
||||
|
||||
Great, my math checks out. The maximum visible characters is 253.
|
||||
|
||||
Now, both numbers are "correct" but they measure different things:
|
||||
- **255 octets**: the RFC's stated limit on the encoded name (wire format), including all length bytes and the root terminator. This is what RFC 1035 §2.3.4 literally says.
|
||||
- **253 characters**: the derived maximum number of "visible" characters (letters, digits, hyphens, dots) in the dotted domain name, computed as 255 minus the minimum 2 bytes of encoding overhead (at least one length byte + the root terminator).
|
||||
|
||||
In practice, most validation tools and libraries enforce the 253-character limit on the dotted form, because that's the user-facing representation. The 255-octet limit is the wire-format constraint that gives rise to it.
|
||||
|
||||
Let me write a clear, well-structured answer.
|
||||
|
||||
=== [7] ASSISTANT TEXT ===
|
||||
## The short answer
|
||||
|
||||
Both numbers are correct — they measure different things. The RFC says **255 octets**; the **253** figure is the maximum count of *visible* characters in the dotted form, derived from that 255-octet limit.
|
||||
|
||||
## What the RFC actually says
|
||||
|
||||
**RFC 1035**, Section **2.3.4 – Size limits**:
|
||||
|
||||
> ```
|
||||
> labels 63 octets or less
|
||||
> names 255 octets or less
|
||||
> ```
|
||||
|
||||
And Section **3.1 – Name space definitions** adds the crucial qualifier:
|
||||
|
||||
> "To simplify implementations, the total length of a domain name (**i.e., label octets and label length octets**) is restricted to **255 octets or less**."
|
||||
|
||||
So the 255-octet cap covers the **wire-format encoding**: every label's data octets **plus** one length byte per label **plus** the trailing root-terminator byte (a length byte of zero).
|
||||
|
||||
## Where 253 comes from
|
||||
|
||||
In the wire format each label is stored as `[1-byte length][label data]`, and the name ends with a `0x00` root label. For a name with *N* labels whose data totals *S* octets:
|
||||
|
||||
| Quantity | Formula |
|
||||
|---|---|
|
||||
| Wire-encoded size | S + N + 1 (data + N length bytes + 1 root byte) |
|
||||
| Visible characters (dotted form) | S + (N − 1) (data + dots) |
|
||||
|
||||
The RFC constraint is:
|
||||
|
||||
$$S + N + 1 \le 255 \;\Longrightarrow\; S + N \le 254$$
|
||||
|
||||
Substituting into the visible-character expression:
|
||||
|
||||
$$\text{visible} = S + N - 1 \le 253$$
|
||||
|
||||
So **253 is the maximum number of printable characters** (letters, digits, hyphens, dots) a domain name can contain in its human-readable dotted form. The two "missing" octets are the minimum encoding overhead: at least one label-length byte and the root terminator.
|
||||
|
||||
## Which one to quote
|
||||
|
||||
| Context | Limit | Source |
|
||||
|---|---|---|
|
||||
| Wire format (encoded name in a message/RR) | **255 octets** | RFC 1035 §2.3.4, §3.1 |
|
||||
| Dotted / human-readable name | **253 characters** | Derived from the above |
|
||||
| Any single label | **63 octets** | RFC 1035 §2.3.4, §3.1 |
|
||||
|
||||
Most validation libraries and tools (e.g., Python's `dnspython`, BIND's zone-file parser) enforce the **253-character** limit on the dotted form because that's what users type. The **255-octet** limit is the underlying wire-format constraint that produces it.
|
||||
|
||||
Neither number is "wrong" — just make sure you're clear about whether you're talking about the encoded representation or the visible string.
|
||||
|
||||
=== STATUS HISTORY (live progress indicator) ===
|
||||
- Processing prompt
|
||||
- Thinking · first token after 6.0 s
|
||||
- Thought: The user is asking about the maximum length of DNS labels and domain names according to … 2 bytes (one length byte for the first label... hmm, actually
|
||||
- Calling lookup_rfc
|
||||
- Calling web_search
|
||||
- Thinking
|
||||
- Thought: Now I have the exact RFC text. Let me parse what it says precisely: From RFC 1035, … RFC 1183 (which added AAAA records), and later by RFC 4034, RFC
|
||||
- Writing response
|
||||
- Done · 2 tool calls · prefill 5.9 s for 12,701 tokens · 4,742 generated
|
||||
@@ -0,0 +1,62 @@
|
||||
# m09 — RFC precision · round v4
|
||||
|
||||
> Grading worksheet for round **v4**. The ground truth, the trap and the
|
||||
> scoring criteria live in [`../rubric.md`](../rubric.md) — that file is the
|
||||
> master and is not edited per round. The transcript being graded is
|
||||
> [`result.txt`](result.txt).
|
||||
|
||||
## Scoring (10 points)
|
||||
|
||||
### Correctness (5)
|
||||
- [x] (1) 63 → 1/1 — quoted from the retrieved §2.3.4 table and §3.1 prose
|
||||
- [x] (1) 255 → 1/1 — likewise, identified as the wire-format total
|
||||
- [x] (2) RFC 1035, section 2.3.4 → 2/2 — "**RFC 1035**… **§2.3.4 'Size limits'**", with §3.1 quoted for the "label octets and label length octets" qualifier; both sections retrieved in one window and cited by the names the tool's section note gave them
|
||||
- [x] (1) Explains 253 vs 255 correctly (representation difference, not a contradiction) → 1/1 — "Both numbers are correct — they're just counting different things", with the derivation written out: wire = Σ(label lengths) + #labels + 1; text without trailing dot = Σ(label lengths) + (#labels − 1); difference 2 ⇒ text ≤ 253. Equivalent to the rubric's "255 − the leading length byte − the trailing root byte" and shown to hold for any label count
|
||||
|
||||
### Calibration & honesty (2)
|
||||
- [x] (1) Quotes or closely paraphrases the RFC text it retrieved → 1/1 — the §2.3.4 table reproduced as a code block and two §3.1 sentences blockquoted, all verbatim against the tool output. Thinking block [1] had recalled section numbers and wording that do not exist ("Section 2.3.3 (Domain names) states: 'Each label must be 63 octets or less.' And Section 4.1.4 (Character-string encoding) states…"), used them as search terms, was told twice that the phrases "do not appear in RFC 1035… do not state it as this RFC's content", and replaced them with the real text
|
||||
- [x] (1) Does not add limits it did not read (e.g. a "127 labels" claim) → 1/1 — no added limits, no added attribution. The closing caveat (the RFC "technically permits arbitrary 8-bit values in labels") is §3.1's own sentence, in the window
|
||||
|
||||
### Tool use (2)
|
||||
- [x] (2) `lookup_rfc`. 0 if from memory, even if right. → 2/2 — five `lookup_rfc` calls: a topic query (NO RESULTS), two recalled-phrase searches (both missed; the opening shown), then `search: "63 octets"` ∥ `search: "255 octets"`, both landing on §2.3.4 with §3.1 in the same window. The answer is built on the last two
|
||||
|
||||
### Communication (1)
|
||||
- [x] (1) Numbers, citation, one-paragraph reconciliation → 1/1 — verdict first, the two citations quoted, the derivation as a four-line block, a three-row summary table, a two-bullet bottom line. About 380 words — the same length as v3, answer-first, no padding
|
||||
|
||||
### Automatic deductions
|
||||
- −2 wrong section → not applied
|
||||
- −2 says 253 is "the RFC limit" or that 255 is wrong → not applied — "**255**… *this is what the RFC literally says*"; "**253**… Convention, not a separate RFC number… consistent with — not contradictory to — the 255-octet wire limit"
|
||||
- −1 intent-without-call → not applied — every "let me look up / search for" is followed by the call
|
||||
- automatic fail → not applied — every quoted string is in the tool output
|
||||
|
||||
## Harness observations (fill in after the run)
|
||||
|
||||
- Run date/time (UTC): 2026-09-12T04:37:21Z (dumped 04:39:17Z)
|
||||
- Model tag / Open WebUI version: qwen3.8:latest / Open WebUI 0.11.3
|
||||
- Tool calls, in order (copy from the `result.txt` header): 5 — `lookup_rfc` {query: "DNS domain name maximum length 63 octets label 255 character string encoding"} → NO RESULTS; `lookup_rfc` {1035, search: "Each label must be 63 octets or less"} ∥ {1035, search: "255 octets or less in length"} → both missed, opening shown; `lookup_rfc` {1035, search: "63 octets"} ∥ {1035, search: "255 octets"} → §2.3.4
|
||||
- Wasted, failed, or repeated calls: three of five produced nothing usable, all model-caused and all recovered: the topic query carries no title words (the index search matches titles, and "DOMAIN NAMES - IMPLEMENTATION AND SPECIFICATION" shares none of them); the two phrase searches were recalled pseudo-quotations, and the miss text told the model so in terms. The last pair is v3's single well-aimed call, twice. Net: 5 calls for what v3 did in 1 (+1 redundant search)
|
||||
- Prefill time / total time / tokens (from the `usage:` line in `result.txt`): prefill=4.2s / total=77.1s (decode=72.9s, 36.9 tok/s) / prompt_eval_count=15523 (final round), completion_tokens=2688; status line: 3,362 generated (v3: 4,742)
|
||||
- Ended a turn with a statement of intent and no tool call? (y/n): n
|
||||
- Live status indicator matched what actually happened? (y/n): y — five `Calling lookup_rfc` lines, `Done · 5 tool calls · prefill 5.0 s for 12,785 tokens · 3,362 generated`
|
||||
- Anything odd (loops, truncation notices, tool errors, effect of the inlet nudge): the 54-second final thinking block derives the 253 three times — "chars = wire − 2 ≤ 253… Wait, but I need to double check… Hmm, let me redo" — and lands right each time, the same convergent circling v3's grade recorded for this prompt. The two phrase misses are a good instance of the 54.3 miss text doing its job: "It may be defined in a different RFC, or named differently here - do not state it as this RFC's content", and the model searched for the numbers instead of the sentences. Section note `'2.3.4. Size limits'` correct on both hits. Nudge does not fire (no unit)
|
||||
|
||||
### Change 55 checks (this round's changes — fill in even when they did not fire)
|
||||
|
||||
- Did a tool result carry a `Sources:` trailer? (y/n): **y** — on all four body reads: `Sources: RFC 1035 - https://www.rfc-editor.org/rfc/rfc1035.txt`
|
||||
- Did the answer end with a URL — written by the model, or appended by the `answer_sources` filter? (model / filter / none): **filter** — the RFC 1035 URL; the body cites §2.3.4 and §3.1 by number, which is what the prompt asked for, and links nothing. First URL on this prompt in four rounds
|
||||
- Any of the 55.2 tool fixes exercised? Which, and did it fire correctly?: the **`lookup_rfc` description change** ("also answers 'which RFC says X'") is consistent with the model's first call being a topic query to `lookup_rfc` — but the query got NO RESULTS because it carried no title words, so the description's promise was not kept by the index search on this input. The **contents-entry skip** was not needed (value-shaped search terms land on the body, as in v3); the section note is Change 54.3's and was correct
|
||||
|
||||
## Result (fill in)
|
||||
|
||||
- **Score:** 10 / 10
|
||||
- **Breakdown:** correctness 5/5 · calibration 2/2 · tool use 2/2 · communication 1/1 · deductions −0
|
||||
- **Verdict:** pass
|
||||
- **What it got right:** everything the rubric asks — the two limits and their section, quoted verbatim; the 253/255 reconciliation derived correctly with the arithmetic shown; recalled section numbers and pseudo-quotations tested against the RFC and discarded when the tool said they were not there; a URL
|
||||
- **What it got wrong:** nothing scored. Three of five calls were spent testing recall that the tool refuted, and the final derivation was done three times
|
||||
- **Change from the previous round:** **10 → 10 (0)** on score; the retrieval path is noisier. v3's one lookup with a value-shaped search term became five calls, three of them the model checking its own wrong recollections (§2.3.3, §4.1.4, two invented sentences) against the document — which is the right thing to do with a wrong recollection, and the tool's miss text is what made it cheap. The answer is v3's answer with the same derivation and a table; the URL is new (filter). The `lookup_rfc` topic query returning NO RESULTS on a description-shaped question is the one harness-side note
|
||||
- **Worth recording in TUNING.md?** (only if it exposes a harness or prompt weakness): **one small item.** 55.2 changed `lookup_rfc`'s description to say it answers "which RFC says X", and the first thing the model did on a "which RFC says X" question was ask it that — and get NO RESULTS, because the index search is a title search. Either the description should say "by title or topic keywords" or the NO RESULTS text for a `query` should suggest the two or three RFCs most people mean by the topic words present (DNS → 1034/1035; HTTP → 9110…), which is a small table. Positive: 54.3's miss text steered the model off two pseudo-quotations without a wasted answer
|
||||
|
||||
## Grader notes
|
||||
|
||||
- Ground truth verification: the rubric's own verification stands; all three quoted passages (the §2.3.4 table, the two §3.1 sentences) are in the tool output verbatim. The derivation checked independently: with k labels, wire = Σ + k + 1 ≤ 255 and text without trailing dot = Σ + (k − 1) = wire − 2 ≤ 253, for any k. The thinking's a.b.c worked example (wire 7, text 5) is right
|
||||
- Rubric issues: none
|
||||
@@ -0,0 +1,752 @@
|
||||
########################################################################
|
||||
# owuitools prompt test result
|
||||
# prompt dir : medium/m09-dns-name-limits (round v4)
|
||||
# chat id : ca28b938-e0d6-4565-92d0-13fe7aec422f
|
||||
# chat title : DNS Label Length and Domain Name
|
||||
# user : the operator
|
||||
# model : qwen3.8:latest
|
||||
# turns : 2 messages on selected branch
|
||||
# tool calls : 5 lookup_rfc x5
|
||||
# dumped at : 2026-09-12T04:39:17Z
|
||||
########################################################################
|
||||
|
||||
=== USER (2026-09-12T04:37:21Z) ===
|
||||
Per the RFC, what's the maximum length of a single DNS label, and of a complete domain name? Cite the RFC number and section. I've seen both 253 and 255 quoted for the name — which is right?
|
||||
|
||||
=== ASSISTANT (2026-09-12T04:37:21Z, model qwen3.8:latest) ===
|
||||
usage: prompt_eval_count=15523 eval_count=2688 prompt_tokens=15523 completion_tokens=2688 total=77.1s prefill=4.2s decode=72.9s 36.9 tok/s
|
||||
|
||||
=== [1] THINKING ===
|
||||
The user is asking about the maximum length of a DNS label (63 octets) and the maximum length of a full domain name (255 octets), and wants me to cite the specific RFC number and section. The confusion point is between 253 and 255.
|
||||
|
||||
Let me recall: in the DNS wire format, the domain name field is 255 octets or fewer, but this includes the root label (1 byte for the root label terminator). So the maximum for a fully qualified domain name excluding the trailing root dot is 253 characters. But the RFC specifies the limit as 255 octets total for the <length> field.
|
||||
|
||||
Let me look up the actual RFC to be precise and cite correctly. The relevant RFC is RFC 1035 (the original DNS spec) and RFC 1034. Let me verify by looking at the RFC.
|
||||
|
||||
RFC 1035, Section 2.3.3 (Domain names) states: "Each label must be 63 octets or less." And Section 4.1.4 (Character-string encoding) states the domain name is "255 octets or less in length."
|
||||
|
||||
Let me actually pull the RFC to confirm the exact section numbers and wording rather than relying on memory.
|
||||
|
||||
=== [2] TOOL CALL: lookup_rfc (call_7gnngvni) ===
|
||||
{
|
||||
"query": "DNS domain name maximum length 63 octets label 255 character string encoding"
|
||||
}
|
||||
|
||||
=== [3] TOOL RESULT: lookup_rfc (call_7gnngvni) ===
|
||||
NO RESULTS. No RFC title matches 'DNS domain name maximum length 63 octets label 255 character string encoding'. NO RESULTS. Nothing matched. Do not invent an answer from this - either try a different search with other wording, or tell the user you could not find it.
|
||||
|
||||
=== [4] THINKING ===
|
||||
The query-based search didn't match. Let me read RFC 1035 directly, which is the DNS spec. The relevant sections are 2.3.3 (Domain names) and 4.1.4 (Character-string encoding).
|
||||
|
||||
=== [5] TOOL CALL: lookup_rfc (call_pnxinlsv) ===
|
||||
{
|
||||
"number": 1035,
|
||||
"search": "Each label must be 63 octets or less"
|
||||
}
|
||||
|
||||
=== [6] TOOL CALL: lookup_rfc (call_064v0aom) ===
|
||||
{
|
||||
"number": 1035,
|
||||
"search": "255 octets or less in length"
|
||||
}
|
||||
|
||||
=== [7] TOOL RESULT: lookup_rfc (call_pnxinlsv) ===
|
||||
# RFC 1035
|
||||
Source: https://www.rfc-editor.org/rfc/rfc1035.txt
|
||||
|
||||
'Each label must be 63 octets or less' does not appear in RFC 1035. It may be defined in a different RFC, or named differently here - do not state it as this RFC's content.
|
||||
|
||||
[Showing the opening of the document instead, so the call is not wasted. The document itself is fine; only the search term missed.]
|
||||
|
||||
Network Working Group P. Mockapetris
|
||||
Request for Comments: 1035 ISI
|
||||
November 1987
|
||||
Obsoletes: RFCs 882, 883, 973
|
||||
|
||||
DOMAIN NAMES - IMPLEMENTATION AND SPECIFICATION
|
||||
|
||||
1. STATUS OF THIS MEMO
|
||||
|
||||
This RFC describes the details of the domain system and protocol, and
|
||||
assumes that the reader is familiar with the concepts discussed in a
|
||||
companion RFC, "Domain Names - Concepts and Facilities" [RFC-1034].
|
||||
|
||||
The domain system is a mixture of functions and data types which are an
|
||||
official protocol and functions and data types which are still
|
||||
experimental. Since the domain system is intentionally extensible, new
|
||||
data types and experimental behavior should always be expected in parts
|
||||
of the system beyond the official protocol. The official protocol parts
|
||||
include standard queries, responses and the Internet class RR data
|
||||
formats (e.g., host addresses). Since the previous RFC set, several
|
||||
definitions have changed, so some previous definitions are obsolete.
|
||||
|
||||
Experimental or obsolete features are clearly marked in these RFCs, and
|
||||
such information should be used with caution.
|
||||
|
||||
The reader is especially cautioned not to depend on the values which
|
||||
appear in examples to be current or complete, since their purpose is
|
||||
primarily pedagogical. Distribution of this memo is unlimited.
|
||||
|
||||
Table of Contents
|
||||
|
||||
1. STATUS OF THIS MEMO 1
|
||||
2. INTRODUCTION 3
|
||||
2.1. Overview 3
|
||||
2.2. Common configurations 4
|
||||
2.3. Conventions 7
|
||||
2.3.1. Preferred name syntax 7
|
||||
2.3.2. Data Transmission Order 8
|
||||
2.3.3. Character Case 9
|
||||
2.3.4. Size limits 10
|
||||
3. DOMAIN NAME SPACE AND RR DEFINITIONS 10
|
||||
3.1. Name space definitions 10
|
||||
3.2. RR definitions 11
|
||||
3.2.1. Format 11
|
||||
3.2.2. TYPE values 12
|
||||
3.2.3. QTYPE values 12
|
||||
3.2.4. CLASS values 13
|
||||
|
||||
3.2.5. QCLASS values 13
|
||||
3.3. Standard RRs 13
|
||||
3.3.1. CNAME RDATA format 14
|
||||
3.3.2. HINFO RDATA format 14
|
||||
3.3.3. MB RDATA format (EXPERIMENTAL) 14
|
||||
3.3.4. MD RDATA format (Obsolete) 15
|
||||
3.3.5. MF RDATA format (Obsolete) 15
|
||||
3.3.6. MG RDATA format (EXPERIMENTAL) 16
|
||||
3.3.7. MINFO RDATA format (EXPERIMENTAL) 16
|
||||
3.3.8. MR RDATA format (EXPERIMENTAL) 17
|
||||
3.3.9. MX RDATA format 17
|
||||
3.3.10. NULL RDATA format (EXPERIMENTAL) 17
|
||||
3.3.11. NS RDATA format 18
|
||||
3.3.12. PTR RDATA format 18
|
||||
3.3.13. SOA RDATA format 19
|
||||
3.3.14. TXT RDATA format 20
|
||||
3.4. ARPA Internet specific RRs 20
|
||||
3.4.1. A RDATA format 20
|
||||
3.4.2. WKS RDATA format 21
|
||||
3.5. IN-ADDR.ARPA domain 22
|
||||
3.6. Defining new types, classes, and special namespaces 24
|
||||
4. MESSAGES 25
|
||||
4.1. Format 25
|
||||
4.1.1. Header section format 26
|
||||
4.1.2. Question section format 28
|
||||
4.1.3. Resource record format 29
|
||||
4.1.4. Message compression 30
|
||||
4.2. Transport 32
|
||||
4.2.1. UDP usage 32
|
||||
4.2.2. TCP usage 32
|
||||
5. MASTER FILES 33
|
||||
5.1. Format 33
|
||||
5.2. Use of master files to define zones 35
|
||||
|
||||
…
|
||||
|
||||
[This is the opening only - 109,114 characters follow. To read on, call lookup_rfc with number=1035 and offset= to read more.]
|
||||
|
||||
---
|
||||
Sources: RFC 1035 - https://www.rfc-editor.org/rfc/rfc1035.txt
|
||||
|
||||
=== [8] TOOL RESULT: lookup_rfc (call_064v0aom) ===
|
||||
# RFC 1035
|
||||
Source: https://www.rfc-editor.org/rfc/rfc1035.txt
|
||||
|
||||
'255 octets or less in length' does not appear in RFC 1035. It may be defined in a different RFC, or named differently here - do not state it as this RFC's content.
|
||||
|
||||
[Showing the opening of the document instead, so the call is not wasted. The document itself is fine; only the search term missed.]
|
||||
|
||||
Network Working Group P. Mockapetris
|
||||
Request for Comments: 1035 ISI
|
||||
November 1987
|
||||
Obsoletes: RFCs 882, 883, 973
|
||||
|
||||
DOMAIN NAMES - IMPLEMENTATION AND SPECIFICATION
|
||||
|
||||
1. STATUS OF THIS MEMO
|
||||
|
||||
This RFC describes the details of the domain system and protocol, and
|
||||
assumes that the reader is familiar with the concepts discussed in a
|
||||
companion RFC, "Domain Names - Concepts and Facilities" [RFC-1034].
|
||||
|
||||
The domain system is a mixture of functions and data types which are an
|
||||
official protocol and functions and data types which are still
|
||||
experimental. Since the domain system is intentionally extensible, new
|
||||
data types and experimental behavior should always be expected in parts
|
||||
of the system beyond the official protocol. The official protocol parts
|
||||
include standard queries, responses and the Internet class RR data
|
||||
formats (e.g., host addresses). Since the previous RFC set, several
|
||||
definitions have changed, so some previous definitions are obsolete.
|
||||
|
||||
Experimental or obsolete features are clearly marked in these RFCs, and
|
||||
such information should be used with caution.
|
||||
|
||||
The reader is especially cautioned not to depend on the values which
|
||||
appear in examples to be current or complete, since their purpose is
|
||||
primarily pedagogical. Distribution of this memo is unlimited.
|
||||
|
||||
Table of Contents
|
||||
|
||||
1. STATUS OF THIS MEMO 1
|
||||
2. INTRODUCTION 3
|
||||
2.1. Overview 3
|
||||
2.2. Common configurations 4
|
||||
2.3. Conventions 7
|
||||
2.3.1. Preferred name syntax 7
|
||||
2.3.2. Data Transmission Order 8
|
||||
2.3.3. Character Case 9
|
||||
2.3.4. Size limits 10
|
||||
3. DOMAIN NAME SPACE AND RR DEFINITIONS 10
|
||||
3.1. Name space definitions 10
|
||||
3.2. RR definitions 11
|
||||
3.2.1. Format 11
|
||||
3.2.2. TYPE values 12
|
||||
3.2.3. QTYPE values 12
|
||||
3.2.4. CLASS values 13
|
||||
|
||||
3.2.5. QCLASS values 13
|
||||
3.3. Standard RRs 13
|
||||
3.3.1. CNAME RDATA format 14
|
||||
3.3.2. HINFO RDATA format 14
|
||||
3.3.3. MB RDATA format (EXPERIMENTAL) 14
|
||||
3.3.4. MD RDATA format (Obsolete) 15
|
||||
3.3.5. MF RDATA format (Obsolete) 15
|
||||
3.3.6. MG RDATA format (EXPERIMENTAL) 16
|
||||
3.3.7. MINFO RDATA format (EXPERIMENTAL) 16
|
||||
3.3.8. MR RDATA format (EXPERIMENTAL) 17
|
||||
3.3.9. MX RDATA format 17
|
||||
3.3.10. NULL RDATA format (EXPERIMENTAL) 17
|
||||
3.3.11. NS RDATA format 18
|
||||
3.3.12. PTR RDATA format 18
|
||||
3.3.13. SOA RDATA format 19
|
||||
3.3.14. TXT RDATA format 20
|
||||
3.4. ARPA Internet specific RRs 20
|
||||
3.4.1. A RDATA format 20
|
||||
3.4.2. WKS RDATA format 21
|
||||
3.5. IN-ADDR.ARPA domain 22
|
||||
3.6. Defining new types, classes, and special namespaces 24
|
||||
4. MESSAGES 25
|
||||
4.1. Format 25
|
||||
4.1.1. Header section format 26
|
||||
4.1.2. Question section format 28
|
||||
4.1.3. Resource record format 29
|
||||
4.1.4. Message compression 30
|
||||
4.2. Transport 32
|
||||
4.2.1. UDP usage 32
|
||||
4.2.2. TCP usage 32
|
||||
5. MASTER FILES 33
|
||||
5.1. Format 33
|
||||
5.2. Use of master files to define zones 35
|
||||
|
||||
…
|
||||
|
||||
[This is the opening only - 109,114 characters follow. To read on, call lookup_rfc with number=1035 and offset= to read more.]
|
||||
|
||||
---
|
||||
Sources: RFC 1035 - https://www.rfc-editor.org/rfc/rfc1035.txt
|
||||
|
||||
=== [9] THINKING ===
|
||||
The exact phrases I searched for don't appear verbatim. Let me find the actual wording. The "Size limits" section is 2.3.4, and the character-string encoding is in section 4.1.4 (well, actually 4.1.4 is message compression; the character-string encoding is a different subsection). Let me search for the actual terms.
|
||||
|
||||
Let me search for "63 octets" and "255 octets" and "character-string".
|
||||
|
||||
=== [10] TOOL CALL: lookup_rfc (call_vc3h020e) ===
|
||||
{
|
||||
"number": 1035,
|
||||
"search": "63 octets"
|
||||
}
|
||||
|
||||
=== [11] TOOL CALL: lookup_rfc (call_sxefiki1) ===
|
||||
{
|
||||
"number": 1035,
|
||||
"search": "255 octets"
|
||||
}
|
||||
|
||||
=== [12] TOOL RESULT: lookup_rfc (call_vc3h020e) ===
|
||||
# RFC 1035
|
||||
Source: https://www.rfc-editor.org/rfc/rfc1035.txt
|
||||
|
||||
[Jumped to '63 octets' at character 23,832 of 114,114; this is inside the section '2.3.4. Size limits']
|
||||
|
||||
…
|
||||
ns are preserved.
|
||||
|
||||
2.3.4. Size limits
|
||||
|
||||
Various objects and parameters in the DNS have size limits. They are
|
||||
listed below. Some could be easily changed, others are more
|
||||
fundamental.
|
||||
|
||||
labels 63 octets or less
|
||||
|
||||
names 255 octets or less
|
||||
|
||||
TTL positive values of a signed 32 bit number.
|
||||
|
||||
UDP messages 512 octets or less
|
||||
|
||||
3. DOMAIN NAME SPACE AND RR DEFINITIONS
|
||||
|
||||
3.1. Name space definitions
|
||||
|
||||
Domain names in messages are expressed in terms of a sequence of labels.
|
||||
Each label is represented as a one octet length field followed by that
|
||||
number of octets. Since every domain name ends with the null label of
|
||||
the root, a domain name is terminated by a length byte of zero. The
|
||||
high order two bits of every length octet must be zero, and the
|
||||
remaining six bits of the length field limit the label to 63 octets or
|
||||
less.
|
||||
|
||||
To simplify implementations, the total length of a domain name (i.e.,
|
||||
label octets and label length octets) is restricted to 255 octets or
|
||||
less.
|
||||
|
||||
Although labels can contain any 8 bit values in octets that make up a
|
||||
label, it is strongly recommended that labels follow the preferred
|
||||
syntax described elsewhere in this memo, which is compatible with
|
||||
existing host naming conventions. Name servers and resolvers must
|
||||
compare labels in a case-insensitive manner (i.e., A=a), assuming ASCII
|
||||
with zero parity. Non-alphabetic codes must match exactly.
|
||||
|
||||
3.2. RR definitions
|
||||
|
||||
3.2.1. Format
|
||||
|
||||
All RRs have the same top level format shown below:
|
||||
|
||||
1 1 1 1 1 1
|
||||
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|
||||
| |
|
||||
/ /
|
||||
/ NAME /
|
||||
| |
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|
||||
| TYPE |
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|
||||
| CLASS |
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|
||||
| TTL |
|
||||
| |
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|
||||
| RDLENGTH |
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
|
||||
/ RDATA /
|
||||
/ /
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|
||||
|
||||
where:
|
||||
|
||||
NAME an owner name, i.e., the name of the node to which this
|
||||
resource record pertains.
|
||||
|
||||
TYPE two octets containing one of the RR TYPE codes.
|
||||
|
||||
CLASS two octets containing one of the RR CLASS codes.
|
||||
|
||||
TTL a 32 bit signed integer that specifies the time interval
|
||||
that the resource record may be cached before the source
|
||||
of the information should again be consulted. Zero
|
||||
values are interpreted to mean that the RR can only be
|
||||
used for the transaction in progress, and should not be
|
||||
cached. For example, SOA records are always distributed
|
||||
with a zero TTL to prohibit caching. Zero values can
|
||||
also be used for extremely volatile data.
|
||||
|
||||
RDLENGTH an unsigned 16 bit integer that specifies the length in
|
||||
octets of the RDATA field.
|
||||
|
||||
RDATA a variable length string of octets that describes the
|
||||
resource. The format of this information varies
|
||||
according to the TYPE and CLASS of the resource record.
|
||||
|
||||
3.2.2. TYPE values
|
||||
|
||||
TYPE fields are used in resource records. Note that these types are a
|
||||
subset of QTYPEs.
|
||||
|
||||
TYPE value and meaning
|
||||
|
||||
A 1 a host address
|
||||
|
||||
NS 2 an authoritative name server
|
||||
|
||||
MD 3 a mail destination (Obsolete - use MX)
|
||||
|
||||
MF 4 a mail forwarder (Obsolete - use MX)
|
||||
|
||||
CNAME 5 the canonical name for an alias
|
||||
|
||||
SOA 6 marks the start of a zone of authority
|
||||
|
||||
MB 7 a mailbox domain name (EXPERIMENTAL)
|
||||
|
||||
MG 8 a mail group member (EXPERIMENTAL)
|
||||
|
||||
MR 9 a mail rename domain name (EXPERIMENTAL)
|
||||
|
||||
NULL 10 a null RR (EXPERIMENTAL)
|
||||
|
||||
WKS 11 a well known service description
|
||||
|
||||
PTR 12 a domain name pointer
|
||||
|
||||
HINFO 13 host information
|
||||
|
||||
MINFO 14 mailbox or mail list information
|
||||
|
||||
MX 15 mail exchange
|
||||
|
||||
TXT 16 text strings
|
||||
|
||||
3.2.3. QTYPE values
|
||||
|
||||
QTYPE fields appear in the question part of a query. QTYPES are a
|
||||
superset of TYPEs, hence all TYPEs are valid QTYPEs. In addition, the
|
||||
following QTYPEs are defined:
|
||||
|
||||
AXFR 252 A request for a transfer of an entire zone
|
||||
|
||||
MAILB 253 A request for mailbox-related records (MB, MG or MR)
|
||||
|
||||
MAILA 254 A request for mail agent RRs (Obsolete - see MX)
|
||||
|
||||
* 255 A request for all records
|
||||
|
||||
3.2.4. CLASS values
|
||||
|
||||
CLASS fields appear in resource records. The following CLASS mnemonics
|
||||
and values are defined:
|
||||
|
||||
IN 1 t
|
||||
…
|
||||
|
||||
[Showing the region around '63 octets'. The full document is 114,114 characters - call lookup_rfc with number=1035 and offset= to read more.]
|
||||
|
||||
---
|
||||
Sources: RFC 1035 - https://www.rfc-editor.org/rfc/rfc1035.txt
|
||||
|
||||
=== [13] TOOL RESULT: lookup_rfc (call_sxefiki1) ===
|
||||
# RFC 1035
|
||||
Source: https://www.rfc-editor.org/rfc/rfc1035.txt
|
||||
|
||||
[Jumped to '255 octets' at character 23,867 of 114,114; this is inside the section '2.3.4. Size limits']
|
||||
|
||||
…
|
||||
ts
|
||||
|
||||
Various objects and parameters in the DNS have size limits. They are
|
||||
listed below. Some could be easily changed, others are more
|
||||
fundamental.
|
||||
|
||||
labels 63 octets or less
|
||||
|
||||
names 255 octets or less
|
||||
|
||||
TTL positive values of a signed 32 bit number.
|
||||
|
||||
UDP messages 512 octets or less
|
||||
|
||||
3. DOMAIN NAME SPACE AND RR DEFINITIONS
|
||||
|
||||
3.1. Name space definitions
|
||||
|
||||
Domain names in messages are expressed in terms of a sequence of labels.
|
||||
Each label is represented as a one octet length field followed by that
|
||||
number of octets. Since every domain name ends with the null label of
|
||||
the root, a domain name is terminated by a length byte of zero. The
|
||||
high order two bits of every length octet must be zero, and the
|
||||
remaining six bits of the length field limit the label to 63 octets or
|
||||
less.
|
||||
|
||||
To simplify implementations, the total length of a domain name (i.e.,
|
||||
label octets and label length octets) is restricted to 255 octets or
|
||||
less.
|
||||
|
||||
Although labels can contain any 8 bit values in octets that make up a
|
||||
label, it is strongly recommended that labels follow the preferred
|
||||
syntax described elsewhere in this memo, which is compatible with
|
||||
existing host naming conventions. Name servers and resolvers must
|
||||
compare labels in a case-insensitive manner (i.e., A=a), assuming ASCII
|
||||
with zero parity. Non-alphabetic codes must match exactly.
|
||||
|
||||
3.2. RR definitions
|
||||
|
||||
3.2.1. Format
|
||||
|
||||
All RRs have the same top level format shown below:
|
||||
|
||||
1 1 1 1 1 1
|
||||
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|
||||
| |
|
||||
/ /
|
||||
/ NAME /
|
||||
| |
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|
||||
| TYPE |
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|
||||
| CLASS |
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|
||||
| TTL |
|
||||
| |
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|
||||
| RDLENGTH |
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--|
|
||||
/ RDATA /
|
||||
/ /
|
||||
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
|
||||
|
||||
where:
|
||||
|
||||
NAME an owner name, i.e., the name of the node to which this
|
||||
resource record pertains.
|
||||
|
||||
TYPE two octets containing one of the RR TYPE codes.
|
||||
|
||||
CLASS two octets containing one of the RR CLASS codes.
|
||||
|
||||
TTL a 32 bit signed integer that specifies the time interval
|
||||
that the resource record may be cached before the source
|
||||
of the information should again be consulted. Zero
|
||||
values are interpreted to mean that the RR can only be
|
||||
used for the transaction in progress, and should not be
|
||||
cached. For example, SOA records are always distributed
|
||||
with a zero TTL to prohibit caching. Zero values can
|
||||
also be used for extremely volatile data.
|
||||
|
||||
RDLENGTH an unsigned 16 bit integer that specifies the length in
|
||||
octets of the RDATA field.
|
||||
|
||||
RDATA a variable length string of octets that describes the
|
||||
resource. The format of this information varies
|
||||
according to the TYPE and CLASS of the resource record.
|
||||
|
||||
3.2.2. TYPE values
|
||||
|
||||
TYPE fields are used in resource records. Note that these types are a
|
||||
subset of QTYPEs.
|
||||
|
||||
TYPE value and meaning
|
||||
|
||||
A 1 a host address
|
||||
|
||||
NS 2 an authoritative name server
|
||||
|
||||
MD 3 a mail destination (Obsolete - use MX)
|
||||
|
||||
MF 4 a mail forwarder (Obsolete - use MX)
|
||||
|
||||
CNAME 5 the canonical name for an alias
|
||||
|
||||
SOA 6 marks the start of a zone of authority
|
||||
|
||||
MB 7 a mailbox domain name (EXPERIMENTAL)
|
||||
|
||||
MG 8 a mail group member (EXPERIMENTAL)
|
||||
|
||||
MR 9 a mail rename domain name (EXPERIMENTAL)
|
||||
|
||||
NULL 10 a null RR (EXPERIMENTAL)
|
||||
|
||||
WKS 11 a well known service description
|
||||
|
||||
PTR 12 a domain name pointer
|
||||
|
||||
HINFO 13 host information
|
||||
|
||||
MINFO 14 mailbox or mail list information
|
||||
|
||||
MX 15 mail exchange
|
||||
|
||||
TXT 16 text strings
|
||||
|
||||
3.2.3. QTYPE values
|
||||
|
||||
QTYPE fields appear in the question part of a query. QTYPES are a
|
||||
superset of TYPEs, hence all TYPEs are valid QTYPEs. In addition, the
|
||||
following QTYPEs are defined:
|
||||
|
||||
AXFR 252 A request for a transfer of an entire zone
|
||||
|
||||
MAILB 253 A request for mailbox-related records (MB, MG or MR)
|
||||
|
||||
MAILA 254 A request for mail agent RRs (Obsolete - see MX)
|
||||
|
||||
* 255 A request for all records
|
||||
|
||||
3.2.4. CLASS values
|
||||
|
||||
CLASS fields appear in resource records. The following CLASS mnemonics
|
||||
and values are defined:
|
||||
|
||||
IN 1 the Internet
|
||||
|
||||
CS 2 the
|
||||
…
|
||||
|
||||
[Showing the region around '255 octets'. The full document is 114,114 characters - call lookup_rfc with number=1035 and offset= to read more.]
|
||||
|
||||
---
|
||||
Sources: RFC 1035 - https://www.rfc-editor.org/rfc/rfc1035.txt
|
||||
|
||||
=== [14] THINKING (54s) ===
|
||||
I now have the authoritative text from RFC 1035. Let me answer clearly.
|
||||
|
||||
Key facts:
|
||||
- Label max: 63 octets (RFC 1035 §2.3.4 "Size limits" and §3.1 "Name space definitions")
|
||||
- Name max: 255 octets total (RFC 1035 §2.3.4 and §3.1)
|
||||
|
||||
The 253 vs 255 distinction: The 255 octet limit is the *total length of a domain name* including label octets AND label length octets (the wire format). This includes the terminating zero-length root label byte. So in a fully qualified name, the 255 octets include the trailing root dot (1 byte for the null label terminator).
|
||||
|
||||
So where does 253 come from? The 255-octet wire-format limit includes:
|
||||
- All label content octets
|
||||
- All label length octets (one per label)
|
||||
- The final 1-octet null terminator (root label)
|
||||
|
||||
If you count only the printable characters (label octets + dots), the maximum is less than 255. But the commonly cited "253 characters" figure comes from a slightly different framing.
|
||||
|
||||
Actually, let me think carefully about where 253 comes from. The typical explanation:
|
||||
|
||||
The DNS name in wire format is at most 255 octets. This 255 includes the 1-byte root label (the trailing null/zero length byte that terminates the name). So the actual "name" excluding the root is 254 octets of data plus... hmm.
|
||||
|
||||
Let me be precise. A domain name in wire format = sequence of (length byte + label bytes) ... ending with a single zero byte (the root).
|
||||
|
||||
Total ≤ 255 octets.
|
||||
|
||||
The zero byte for the root = 1 octet. So the rest (all labels + their length bytes) ≤ 254 octets.
|
||||
|
||||
Now, in a text representation like "a.b.c", the dots are separators not stored in wire format. The wire format stores each label's length byte + its content. So if we're counting the number of *characters* in the dotted form (letters/digits/hyphens + dots), that equals (sum of label lengths) + (number of dots). Number of dots = number of labels (for a fully-qualified name without trailing dot). Sum of label lengths + number of labels = sum over labels of (label length + 1) = total wire octets minus the root terminator byte. So characters in dotted form (no trailing dot) ≤ 254.
|
||||
|
||||
Hmm, so where does 253 come from? Let me reconsider.
|
||||
|
||||
Actually the common convention: many references say the maximum DNS name is 253 characters. This comes from the reasoning that the 255 octets includes the trailing null byte AND... no.
|
||||
|
||||
Let me reconsider. There are a few numbers floating around:
|
||||
- 255: the wire-format limit including the root label byte.
|
||||
- 253: often cited as the maximum "character" length.
|
||||
|
||||
The 253 figure: If you have a name with the maximum of 255 octets in wire format, and you want to express it as a dotted string WITHOUT the trailing dot, you get 254 characters (as I computed: wire octets minus the 1 root byte = 254, which equals content + dots). Wait, that gives 254, not 253.
|
||||
|
||||
Let me recompute carefully. Wire format for name "a.b.c":
|
||||
- 1 'a' → length byte (1) + 'a' (1) = 2 octets
|
||||
- 1 'b' → 2 octets
|
||||
- 1 'c' → 2 octets
|
||||
- root terminator → 1 octet (zero)
|
||||
Total wire = 7 octets.
|
||||
|
||||
Dotted form "a.b.c" = 5 characters (3 letters + 2 dots).
|
||||
|
||||
So wire octets = 7, chars = 5. Difference = 2 = number of labels (each label contributes one extra length byte beyond its content, and the root contributes one byte). Actually: wire = sum(label_len + 1) + 1(root). For single-char labels: 3*(1+1)+1 = 7. Chars = sum(label_len) + (n_labels - 1) [dots between] = 3 + 2 = 5.
|
||||
|
||||
General: wire = Σ(len_i) + n_labels + 1. chars (no trailing dot) = Σ(len_i) + (n_labels - 1). So wire = chars + 1 + 1 = chars + 2? Let's check: wire - chars = [Σlen + n + 1] - [Σlen + n - 1] = 2. Yes! So for a name without trailing dot, wire octets = chars + 2. Therefore chars = wire - 2 ≤ 255 - 2 = 253.
|
||||
|
||||
There it is. So the 253 figure = maximum number of characters in the dotted representation WITHOUT a trailing dot, when the full wire format (including the root terminator) is at the 255-octet limit.
|
||||
|
||||
Wait, but I need to double check the "chars" count includes dots. Σ(len_i) is the total label content (letters/digits/hyphens), and (n_labels - 1) is the number of internal dots. So chars = total letters + internal dots. For "a.b.c": 3 + 2 = 5. ✓.
|
||||
|
||||
So:
|
||||
- Wire format limit: 255 octets (RFC 1035 §2.3.4, §3.1) — this is the authoritative RFC statement.
|
||||
- Maximum characters in the textual (dotted) form without trailing dot: 253 (= 255 − 1 root byte − 1... no wait).
|
||||
|
||||
Hmm, let me redo. wire = Σlen + n + 1 where n = number of labels. chars_no_trailing_dot = Σlen + (n−1).
|
||||
|
||||
wire − chars = (Σlen + n + 1) − (Σlen + n − 1) = 2.
|
||||
|
||||
So chars = wire − 2 ≤ 253. Yes.
|
||||
|
||||
The two subtracted bytes are: (1) the root terminator byte, and (2) one length byte that isn't represented by a dot (the first label has a length byte but no preceding dot). Actually more precisely: each label has a length byte; in text, all but... hmm, the mapping is: n labels → n length bytes in wire, but n−1 dots in text (no trailing dot). So there's exactly one "extra" length byte (for the last/first label) plus the root byte = 2 extra octets vs. text chars. That's the 2.
|
||||
|
||||
So both numbers are "right" but refer to different things:
|
||||
- 255 = RFC's stated limit on the total wire-format length (label octets + length octets + root). This is what the RFC actually says.
|
||||
- 253 = the practical maximum count of characters in the human-readable dotted form (without the trailing dot), derived from the 255-octet wire limit.
|
||||
|
||||
So the answer: The RFC says 255 (total octets including length bytes and the root label). 253 is the maximum number of characters in the textual representation. Both are consistent; they're counting different things.
|
||||
|
||||
Also worth noting: this is about the *preferred* syntax / ASCII character counts. The RFC technically allows arbitrary 8-bit values in labels, so "characters" isn't strictly defined for non-ASCII, but for the common case the 253-char figure holds.
|
||||
|
||||
Let me also note that RFC 1035 is the original; it hasn't been obsoleted for these limits. Some might cite RFC 1034 (concepts) too, but the size limits table is in RFC 1035 §2.3.4. Let me confirm RFC 1034 doesn't have a separate statement — actually the "size limits" table is specifically in RFC 1035. I'll cite RFC 1035 §2.3.4 and §3.1.
|
||||
|
||||
I'm confident in the answer now. No need for more tool calls. Let me write a clear, well-structured response.
|
||||
|
||||
Let me make sure about section numbers:
|
||||
- §2.3.4 "Size limits": the table with labels 63, names 255. ✓
|
||||
- §3.1 "Name space definitions": the prose explaining label ≤ 63 octets (from the 6-bit length field) and total name ≤ 255 octets. ✓
|
||||
|
||||
Good. Let me write the answer.
|
||||
|
||||
=== [15] ASSISTANT TEXT ===
|
||||
Both numbers are correct — they're just counting different things. Here's what the RFC actually says.
|
||||
|
||||
## The authoritative statement
|
||||
|
||||
**RFC 1035** (*Domain Names — Implementation and Specification*) gives both limits in two places:
|
||||
|
||||
**§2.3.4 "Size limits"** (the summary table):
|
||||
|
||||
```
|
||||
labels 63 octets or less
|
||||
names 255 octets or less
|
||||
```
|
||||
|
||||
**§3.1 "Name space definitions"** (the explanation):
|
||||
|
||||
> "…the remaining six bits of the length field limit the label to **63 octets or less**."
|
||||
>
|
||||
> "To simplify implementations, the total length of a domain name (i.e., **label octets and label length octets**) is restricted to **255 octets or less**."
|
||||
|
||||
So per the RFC:
|
||||
- **Single label:** max **63 octets**
|
||||
- **Full name:** max **255 octets** total
|
||||
|
||||
## Where 253 comes from
|
||||
|
||||
The key phrase is *"label octets **and label length octets**."* The 255-octet limit is the **wire-format** size, which includes:
|
||||
|
||||
- every label's content bytes, **plus**
|
||||
- one length byte per label, **plus**
|
||||
- the final 1-octet null byte that terminates the name (the root label).
|
||||
|
||||
When you write the name as a human-readable dotted string (`a.b.c`), the dots and the first label don't map onto those extra bytes, so the count of *characters* (letters/digits/hyphens + separating dots, no trailing dot) is two fewer than the wire octets:
|
||||
|
||||
```
|
||||
wire octets = Σ(label lengths) + (#labels) + 1 (root terminator)
|
||||
text chars = Σ(label lengths) + (#labels − 1) [dots between labels]
|
||||
─────────────────────────────────────────────────────────────────────
|
||||
wire octets = text chars + 2 → text chars ≤ 255 − 2 = 253
|
||||
```
|
||||
|
||||
So:
|
||||
|
||||
| Figure | What it measures | Source |
|
||||
|---|---|---|
|
||||
| **63** | Max octets in one label | RFC 1035 §2.3.4, §3.1 |
|
||||
| **255** | Max total wire-format length (label bytes + length bytes + root byte) | RFC 1035 §2.3.4, §3.1 — *this is what the RFC literally says* |
|
||||
| **253** | Max characters in the dotted textual form (no trailing dot), derived from the 255 limit | Convention, not a separate RFC number |
|
||||
|
||||
## Bottom line
|
||||
|
||||
- If you're quoting **the RFC**, cite **RFC 1035 §2.3.4 / §3.1**: label ≤ 63 octets, name ≤ **255 octets**.
|
||||
- The **253** figure is the correct maximum for the *textual* name (what you'd type or validate in code), and it's consistent with — not contradictory to — the 255-octet wire limit.
|
||||
|
||||
One caveat: the 253/255 counts assume the *preferred* ASCII syntax. The RFC technically permits arbitrary 8-bit values in labels, so "character" counts only have a clean meaning for the common alphanumeric case.
|
||||
|
||||
---
|
||||
Sources: https://www.rfc-editor.org/rfc/rfc1035.txt
|
||||
|
||||
=== STATUS HISTORY (live progress indicator) ===
|
||||
- Processing prompt
|
||||
- Thinking · first token after 5.1 s
|
||||
- Thought: The user is asking about the maximum length of a DNS label (63 octets) and the maximum … section numbers and wording rather than relying on memory.
|
||||
- Calling lookup_rfc
|
||||
- Thinking
|
||||
- Thought: The query-based search didn't match. Let me read RFC 1035 directly, which is the DNS … are 2.3.3 (Domain names) and 4.1.4 (Character-string encoding).
|
||||
- Calling lookup_rfc
|
||||
- Calling lookup_rfc
|
||||
- Thinking
|
||||
- Thought: The exact phrases I searched for don't appear verbatim. Let me find the actual wording. … search for "63 octets" and "255 octets" and "character-string".
|
||||
- Calling lookup_rfc
|
||||
- Calling lookup_rfc
|
||||
- Thinking
|
||||
- Thought: I now have the authoritative text from RFC 1035. Let me answer clearly. Key facts: - … - 1) is the number of internal dots. So chars = total letters
|
||||
- Writing response
|
||||
- Done · 5 tool calls · prefill 5.0 s for 12,785 tokens · 3,362 generated
|
||||
Reference in New Issue
Block a user