Handling of Unknown DNS Resource Record (RR) Types
RFC 3597
Document | Type | RFC - Proposed Standard (September 2003; Errata) | |
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Author | Andreas Gustafsson | ||
Last updated | 2020-01-21 | ||
Stream | Internent Engineering Task Force (IETF) | ||
Formats | plain text html pdf htmlized (tools) htmlized with errata bibtex | ||
Stream | WG state | (None) | |
Document shepherd | No shepherd assigned | ||
This information refers to IESG processing after the RFC was initially published: | |||
IESG | IESG state | RFC 3597 (Proposed Standard) | |
Action Holders |
(None)
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Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | Ralph Droms | ||
IESG note | Found error in RFC 3597, new document necessary and will no longer have downref problem. RFC 2163 should be moved to historic, though this can be decoupled from RFC 3597 advancing. | ||
Send notices to | jakob@rfc.se, olaf@ripe.net |
Network Working Group A. Gustafsson Request for Comments: 3597 Nominum Inc. Category: Standards Track September 2003 Handling of Unknown DNS Resource Record (RR) Types Status of this Memo This document specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" (STD 1) for the standardization state and status of this protocol. Distribution of this memo is unlimited. Copyright Notice Copyright (C) The Internet Society (2003). All Rights Reserved. Abstract Extending the Domain Name System (DNS) with new Resource Record (RR) types currently requires changes to name server software. This document specifies the changes necessary to allow future DNS implementations to handle new RR types transparently. 1. Introduction The DNS is designed to be extensible to support new services through the introduction of new resource record (RR) types. In practice, deploying a new RR type currently requires changes to the name server software not only at the authoritative DNS server that is providing the new information and the client making use of it, but also at all slave servers for the zone containing it, and in some cases also at caching name servers and forwarders used by the client. Because the deployment of new server software is slow and expensive, the potential of the DNS in supporting new services has never been fully realized. This memo proposes changes to name servers and to procedures for defining new RR types aimed at simplifying the future deployment of new RR types. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in [RFC 2119]. Gustafsson Standards Track [Page 1] RFC 3597 Handling of Unknown DNS RR Types September 2003 2. Definition An "RR of unknown type" is an RR whose RDATA format is not known to the DNS implementation at hand, and whose type is not an assigned QTYPE or Meta-TYPE as specified in [RFC 2929] (section 3.1) nor within the range reserved in that section for assignment only to QTYPEs and Meta-TYPEs. Such an RR cannot be converted to a type- specific text format, compressed, or otherwise handled in a type- specific way. In the case of a type whose RDATA format is class specific, an RR is considered to be of unknown type when the RDATA format for that combination of type and class is not known. 3. Transparency To enable new RR types to be deployed without server changes, name servers and resolvers MUST handle RRs of unknown type transparently. That is, they must treat the RDATA section of such RRs as unstructured binary data, storing and transmitting it without change [RFC1123]. To ensure the correct operation of equality comparison (section 6) and of the DNSSEC canonical form (section 7) when an RR type is known to some but not all of the servers involved, servers MUST also exactly preserve the RDATA of RRs of known type, except for changes due to compression or decompression where allowed by section 4 of this memo. In particular, the character case of domain names that are not subject to compression MUST be preserved. 4. Domain Name Compression RRs containing compression pointers in the RDATA part cannot be treated transparently, as the compression pointers are only meaningful within the context of a DNS message. Transparently copying the RDATA into a new DNS message would cause the compression pointers to point at the corresponding location in the new message, which now contains unrelated data. This would cause the compressed name to be corrupted. To avoid such corruption, servers MUST NOT compress domain names embedded in the RDATA of types that are class-specific or not well- known. This requirement was stated in [RFC1123] without defining the term "well-known"; it is hereby specified that only the RR types defined in [RFC1035] are to be considered "well-known". Gustafsson Standards Track [Page 2] RFC 3597 Handling of Unknown DNS RR Types September 2003 The specifications of a few existing RR types have explicitly allowed compression contrary to this specification: [RFC2163] specified that compression applies to the PX RR, and [RFC2535] allowed compression in SIG RRs and NXT RRs records. Since this specification disallows compression in these cases, it is an update to [RFC2163] (section 4) and [RFC2535] (sections 4.1.7 and 5.2). Receiving servers MUST decompress domain names in RRs of well-knownShow full document text