draft-ietf-dnsext-rfc2672bis-dname-04.txt   draft-ietf-dnsext-rfc2672bis-dname-05.txt 
DNS Extensions Working Group S. Rose DNS Extensions Working Group S. Rose
Internet-Draft NIST Internet-Draft NIST
Intended status: Standards Track W. Wijngaards Intended status: Standards Track W. Wijngaards
Expires: February 11, 2008 NLnet Labs Expires: March 28, 2008 NLnet Labs
August 10, 2007 September 25, 2007
Update to DNAME Redirection in the DNS Update to DNAME Redirection in the DNS
draft-ietf-dnsext-rfc2672bis-dname-04 draft-ietf-dnsext-rfc2672bis-dname-05
Status of This Memo Status of This Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79. aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
skipping to change at page 1, line 35 skipping to change at page 1, line 35
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt. http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html. http://www.ietf.org/shadow.html.
This Internet-Draft will expire on February 11, 2008. This Internet-Draft will expire on March 28, 2008.
Copyright Notice Copyright Notice
Copyright (C) The IETF Trust (2007). Copyright (C) The IETF Trust (2007).
Abstract Abstract
The DNAME record provides redirection for a sub-tree of the domain The DNAME record provides redirection for a sub-tree of the domain
name tree in the DNS system. That is, all names that end with a name tree in the DNS system. That is, all names that end with a
particular suffix are redirected to another part of the DNS. This is particular suffix are redirected to another part of the DNS. This is
skipping to change at page 3, line 23 skipping to change at page 3, line 23
would be redirected to foo.bar.example.net. would be redirected to foo.bar.example.net.
The DNAME RR is similar to the CNAME RR in that it provides The DNAME RR is similar to the CNAME RR in that it provides
redirection. The CNAME RR only provides redirection for exactly one redirection. The CNAME RR only provides redirection for exactly one
name while the DNAME RR provides redirection for all names in a sub- name while the DNAME RR provides redirection for all names in a sub-
tree of the DNS name tree. tree of the DNS name tree.
This document is an update to the original specification of DNAME in This document is an update to the original specification of DNAME in
RFC 2672 [RFC2672]. DNAME was conceived to help with the problem of RFC 2672 [RFC2672]. DNAME was conceived to help with the problem of
maintaining address-to-name mappings in a context of network maintaining address-to-name mappings in a context of network
renumbering. So that with a careful set-up a renumbering event in renumbering. With a careful set-up, a renumbering event in the
the network causes no change to the authoritative server that has the network causes no change to the authoritative server that has the
address-to-name mappings. Examples in practice are classless reverse address-to-name mappings. Examples in practice are classless reverse
address space delegations and punycode alternates for domain spaces. address space delegations and punycode alternates for domain spaces.
Other usage of DNAME lies in redirection of name spaces. For Other usage of DNAME lies in redirection of name spaces. For
example, a zone administrator may want subtrees of the DNS to contain example, a zone administrator may want subtrees of the DNS to contain
the same information. DNAME is also used for redirection of ENUM the same information. DNAME is also used for redirection of ENUM
domains to another maintaining party. domains to another maintaining party.
This update to DNAME does not change the wire format or the handling This update to DNAME does not change the wire format or the handling
of DNAME Resource Records by existing software. A new UD (Understand of DNAME Resource Records by existing software. A new UD (Understand
Dname) bit in the EDNS flags field can be used to signal that CNAME DNAME) bit in the EDNS flags field can be used to signal that CNAME
synthesis is not needed. Discussion is added on problems that may be synthesis is not needed. Discussion is added on problems that may be
encountered when using DNAME. encountered when using DNAME.
2. The DNAME Resource Record 2. The DNAME Resource Record
2.1. Format 2.1. Format
The DNAME RR has mnemonic DNAME and type code 39 (decimal). The DNAME RR has mnemonic DNAME and type code 39 (decimal).
The format of the DNAME record has not changed from the original The format of the DNAME record has not changed from the original
skipping to change at page 7, line 6 skipping to change at page 7, line 6
record and validate the DNAME record. record and validate the DNAME record.
It does not make sense for the authoritative server to follow the It does not make sense for the authoritative server to follow the
chain of DNAMEs, CNAMEs and wildcards outside of the zone of the chain of DNAMEs, CNAMEs and wildcards outside of the zone of the
query, as modern resolvers will remove out-of-zone information from query, as modern resolvers will remove out-of-zone information from
the answer. the answer.
Resolvers MUST be able to handle a synthesized CNAME TTL of zero or Resolvers MUST be able to handle a synthesized CNAME TTL of zero or
equal to the TTL of the corresponding DNAME record. The TTL of zero equal to the TTL of the corresponding DNAME record. The TTL of zero
means that the CNAME can be discarded immediately after processing means that the CNAME can be discarded immediately after processing
the answer. DNSSEC aware resolvers can set the Understand-DNAME (UD the answer. DNAME aware resolvers can set the Understand-DNAME (UD
bit) to receive a response with only the DNAME RR and no synthesized bit) to receive a response with only the DNAME RR and no synthesized
CNAMEs. CNAMEs.
The UD bit is part of the EDNS extended RCODE and Flags field. It is The UD bit is part of the EDNS extended RCODE and Flags field. It is
used to omit server processing, transmission and resolver processing used to omit server processing, transmission and resolver processing
the unsigned synthesized CNAMEs when DNSSEC validation is performed. of unsigned synthesized CNAMEs. Resolvers can set this in a query to
Resolvers can set this in a query to request omission of the request omission of the synthesized CNAMEs. Servers copy the UD bit
synthesized CNAMEs. Servers copy the UD bit to the response, and can to the response, and can omit synthesized CNAMEs from the answer.
omit synthesized CNAMEs from the answer. Older resolvers do not set Older resolvers do not set the UD bit, and older servers do not copy
the UD bit, and older servers do not copy the UD bit to the answer, the UD bit to the answer, and will not omit synthesized CNAMEs.
and will not omit synthesized CNAMEs.
Updated EDNS extended RCODE and Flags field. Updated EDNS extended RCODE and Flags field.
+0 (MSB) +1 (LSB) +0 (MSB) +1 (LSB)
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
0: | EXTENDED-RCODE | VERSION | 0: | EXTENDED-RCODE | VERSION |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
2: |DO|UD| Z | 2: |DO|UD| Z |
+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+ +--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+--+
 End of changes. 7 change blocks. 
14 lines changed or deleted 13 lines changed or added

This html diff was produced by rfcdiff 1.34. The latest version is available from http://tools.ietf.org/tools/rfcdiff/