Handling of Unknown DNS Resource Record (RR) Types (RFC3597)
Original Publication Date: 2003-Sep-01
Included in the Prior Art Database: 2003-Sep-09
Internet Society Requests For Comment (RFCs)
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.
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 (C) The Internet Society (2003). All Rights Reserved.
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.
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
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-
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.
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
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 invol...