Separate missing zone data from response-size handling
05A truncation rule cannot create unavailable records or replace DNS security and operational work.
Across three chosen budgets, the stricter partial-set rule produces an additional TC indication and possible TCP retry. This is an operational consequence, not measured traffic or an authentication upgrade.
Source for this drawing: RFC 9471 · Read RFC section 2.4 ↗
New to this? Start hereA quick picture + helpful background
A message needs an address.
Think of a packet as a small addressed envelope. Devices pass it onward; transport protocols decide what delivery promises an application gets.
Helpful first, if these ideas are unfamiliar
These pictures are analogies to help you learn. The linked RFC explains the actual rules.
Terms in this drawing
Related RFCs and changes
“Updates” changes part of an earlier RFC. “Obsoletes” replaces it. This list shows selected related documents.
Clarifies that the referral puts available NS addresses in Additional and sets TC=1 when all available in-domain glue cannot fit. This updates the server algorithm; it does not obsolete 1034 or make sibling omission subject to the same mandatory TC rule.
Read the updated RFC section ↗The requirements concern name-server software returning available glue. RFC 9471 does not create or change requirements that glue records be present in zone or registry data (§1). If no usable glue exists in the supplied zone, the server cannot invent it; satisfying an inclusion rule over an empty set does not make a referral useful.
- The requirements concern name-server software returning available glue. RFC 9471 does not create or change requirements that glue records be present in zone or registry data (§1). If no usable glue exists in the supplied zone, the server cannot invent it; satisfying an inclusion rule over an empty set does not make a referral useful.
- The §2.4 observed failure example had glue in the zone that did not fit the UDP response, but no TC indication. It is not the same situation as absent zone data. The RFC says the original servers had been corrected by publication; our figures are fictional reproductions of the mechanism, not claims about a presently broken operator.
- RFC 9471 §3.3 updates RFC 1034 §4.3.2 step 3(b): after putting available NS addresses in the additional section, set TC=1 if all in-domain glue does not fit. This is a targeted update to the server algorithm, not an obsoletion of RFC 1034 or a replacement of DNS.
- Correctly setting TC when only part of the in-domain glue fits can increase UDP truncation and subsequent TCP queries (§5). The comparison shows chosen counters for the same three synthetic cases; it is not traffic telemetry or a new capacity requirement.
- The document adds no new security considerations and has no IANA actions (§§4,6). It does not add DNSSEC validation, encryption, server authentication or authority for the website’s answer merely by including glue. Existing DNS security checks remain outside this diagram/helper.
Fictional DNS examples use documentation names and addresses. Record blocks and remaining budgets are schematic supplied costs, not a DNS wire encoder or a complete resolver.
Read the RFC section ↗