

Network Working Group                                             J. Yao
Internet-Draft                                                    X. Lee
Intended status: Standards Track                                   CNNIC
Expires: February 12, 2011                                      P. Vixie
                                            Internet Software Consortium
                                                         August 11, 2010


                      Bundle DNS Name Redirection
                     draft-yao-dnsext-bname-04.txt

Abstract

   This document defines a new DNS Resource Record called "BNAME", which
   provides the capability to map itself and its subtree of the DNS name
   space to another domain.  It differs from the CNAME record which only
   maps a single node of the DNS name space, from the DNAME which only
   maps the subtree of the DNS name space to another domain.

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on February 12, 2011.

Copyright Notice

   Copyright (c) 2010 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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   include Simplified BSD License text as described in Section 4.e of



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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
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   it for publication as an RFC or to translate it into languages other
   than English.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Terminology  . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Motivation . . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  The BNAME Resource Record  . . . . . . . . . . . . . . . . . .  4
     3.1.  Format . . . . . . . . . . . . . . . . . . . . . . . . . .  4
     3.2.  The BNAME Substitution . . . . . . . . . . . . . . . . . .  4
     3.3.  The BNAME Rules  . . . . . . . . . . . . . . . . . . . . .  4
   4.  Query Processing . . . . . . . . . . . . . . . . . . . . . . .  4
     4.1.  Processing by Servers  . . . . . . . . . . . . . . . . . .  5
     4.2.  Processing by Resolvers  . . . . . . . . . . . . . . . . .  8
   5.  BNAME in DNSSEC  . . . . . . . . . . . . . . . . . . . . . . .  9
     5.1.  BNAME validating . . . . . . . . . . . . . . . . . . . . .  9
     5.2.  BNAME alias algorithm identifiers  . . . . . . . . . . . . 10
   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
   7.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   8.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 11
   9.  Change History . . . . . . . . . . . . . . . . . . . . . . . . 11
     9.1.  draft-yao-dnsext-bname: Version 00 . . . . . . . . . . . . 11
     9.2.  draft-yao-dnsext-bname: Version 01 . . . . . . . . . . . . 11
     9.3.  draft-yao-dnsext-bname: Version 02 . . . . . . . . . . . . 11
     9.4.  draft-yao-dnsext-bname: Version 03 . . . . . . . . . . . . 11
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 12
     10.2. Informative References . . . . . . . . . . . . . . . . . . 13
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 13








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1.  Introduction

   More and more internationalized domain name labels [RFC3490] appear
   in the DNS trees.  Some labels [RFC3743] are equivalent in some
   languages.  The internet users want them to be identical in the DNS
   resolution.  For example, color.exmaple.com==colour.example.com.  The
   BNAME represents for bundle names.  This document defines a new DNS
   Resource Record called "BNAME", which provides the capability to map
   an entire tree of the DNS name space to another domain.  It means
   that the BNAME redirects both itself and its descendants to its
   owner.  The DNAME [RFC2672] and [RFC2672bis] do not redirect itself,
   only the descendants.  The domain name that owns a DNAME record is
   allowed to have other resource record types at that domain name.  The
   domain name that owns a BNAME record is not allowed to have other
   resource record types at that domain name unless they are the DNSSEC
   related resource record types defined in [RFC4033], [RFC4034],
   [RFC4035] and [RFC5155].  A server MAY refuse to load a zone that has
   data at a sub-domain of a domain name owning a BNAME RR or that has
   other data except the DNSSEC related resource record types and BNAME
   at that name.  BNAME is a singleton type, meaning only one BNAME is
   allowed per name except the DNSSEC related resource record types.
   Resolvers, servers and zone content administrators should be cautious
   that usage of BNAME or its combination with CNAME or DNAME may lead
   to form loops.  The loops should be avoided.

1.1.  Terminology

   All the basic terms used in this specification are defined in the
   documents [RFC1034], [RFC1035] and [RFC2672].


2.  Motivation

   In some languages, some characters have the variants, which look
   differently or very similar but are identical in the meaning.  For
   example, Chinese character U+56FD and its variant U+570B look
   differently, but are identical in the meaning.  If Internationalized
   Domain Label" or "IDL" [RFC3743] are composed of variant characters,
   we regard this kind of IDL as the IDL variant.  If these IDL variants
   are put into the DNS for resolution, they are expected to be
   identical in the DNS resolution.  More comprehensible example is that
   we expect color.exmaple.com to be equivalent with the
   colour.exmaple.com in the DNS resolution.  The BNAME Resource Record
   and its processing rules are conceived as a solution to this
   equivalence problem.  Without the BNAME mechanism, current mechanisms
   such as DNAME or CNAME are not enough capable to solve all the
   problems with the emergence of internationalized domain names.  The
   internationalized domain names may have alias or equivalence of the



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   original one.  The BNAME solution provides the solution to both ASCII
   alias names and internationalized domain alias names.


3.  The BNAME Resource Record

3.1.  Format

   The BNAME RR has mnemonic BNAME and type code xx (decimal).  It is
   not class-sensitive.  Its RDATA is comprised of a single field,
   <target>, which contains a fully qualified domain name that must be
   sent in uncompressed form [RFC1035], [RFC3597].  The <target> field
   MUST be present.  The presentation format of <target> is that of a
   domain name [RFC1035].  The wildcards in the BNAME RR SHOULD NOT be
   used.

     <owner> <ttl> <class> BNAME <target>

   The effect of the BNAME RR is the substitution of the record's
   <target> for its owner name, as a suffix of a domain name.  This
   substitution has to be applied for every BNAME RR found in the
   resolution process, which allows fairly lengthy valid chains of BNAME
   RRs.

3.2.  The BNAME Substitution

   A BNAME substitution is performed by replacing the suffix labels of
   the name being sought matching the owner name of the BNAME resource
   record with the string of labels in the RDATA field.  The matching
   labels end with the root label in all cases.  Only whole labels are
   replaced.

3.3.  The BNAME Rules

   There are two rules which governs the use of BNAMEs in a zone file.
   The first one is that there SHOULD be no descendants under the owner
   of the BNAME.  The second one is that no resource records can co-
   exist with the BNAME for the same name except the DNSSEC related
   resource record types.  It means that if a BNAME RR is present at a
   node N, there MUST be no other data except the DNSSEC related
   resource record types at N and no data at any descendant of N. This
   restriction applies only to records of the same class as the BNAME
   record.


4.  Query Processing

   To exploit the BNAME mechanism the name resolution algorithms



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   [RFC1034] must be modified slightly for both servers and resolvers.
   Both modified algorithms incorporate the operation of making a
   substitution on a name (either QNAME or SNAME) under control of a
   BNAME record.  This operation will be referred to as "the BNAME
   substitution".

4.1.  Processing by Servers

   For a server performing non-recursive service steps 3.a, 3.c and 4 of
   section 4.3.2 [RFC1034] are changed to check for a BNAME record, and
   to return certain BNAME records from zone data and the cache.

   If the owner name of the bname is the suffix of the name queryed but
   different, when preparing a response, a server performing a BNAME
   substitution will in all cases include the relevant BNAME RR in the
   answer section.  A CNAME RR is synthesized and included in the answer
   section.  This will help the client to reach the correct DNS data.

   If the owner name of the bname is same with the name queryed, when
   preparing a response, a server performing a BNAME substitution will
   not include the relevant BNAME RR in the answer section unless the
   type queryed is BNAME.  A CNAME RR will be synthesized and included
   in the answer section unless the type queryed is BNAME or the query
   is the DNSSEC query.

   The provided synthesized CNAME RR if there has one, MUST have

























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      The same CLASS as the QCLASS of the query,

      TTL equal to the corresponding BNAME RR,

      An <owner> equal to the QNAME in effect at the moment the BNAME RR
      was encountered, and

      An RDATA field containing the new QNAME formed by the action of
      the BNAME substitution.


   The revised server algorithm is:


   1. Set or clear the value of recursion available in the response
      depending on whether the name server is willing to provide
      recursive service.  If recursive service is available and
      requested via the RD bit in the query, go to step 5, otherwise
      step 2.

   2. Search the available zones for the zone which is the nearest
      ancestor to QNAME.  If such a zone is found, go to step 3,
      otherwise step 4.

   3. Start matching down, label by label, in the zone.  The matching
      process can terminate several ways:

























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     a. If the whole of QNAME is matched, we have found the node.

         If the data at the node is a CNAME, and QTYPE doesn't match
         CNAME, copy the CNAME RR into the answer section of the
         response, change QNAME to the canonical name in the CNAME RR,
         and go back to step 1.

         If the data at the node is a BNAME, and QTYPE doesn't
         match BNAME, copy the BNAME RR and also a corresponding,
         synthesized CNAME RR into the answer section of the
         response, change QNAME to the name carried as RDATA in
         the BNAME RR, and go back to step 1.

         Otherwise, copy all RRs which match QTYPE into the answer
         section and go to step 6.

      b. If a match would take us out of the authoritative data, we have
         a referral.  This happens when we encounter a node with NS RRs
         marking cuts along the bottom of a zone.

         Copy the NS RRs for the subzone into the authority section of
         the reply.  Put whatever addresses are available into the
         additional section, using glue RRs if the addresses are not
         available from authoritative data or the cache.  Go to step 4.

      c. If at some label, a match is impossible (i.e., the
         corresponding label does not exist), look to see whether the
         last label matched has a BNAME record.


         If a BNAME record exists at that point, copy that record into
         the answer section.  If substitution of its <target> for its
         <owner> in QNAME would overflow the legal size for a <domain-
         name>, set RCODE to YXDOMAIN [RFC2136] and exit; otherwise
         perform the substitution and continue.  The server SHOULD
         synthesize a corresponding CNAME record as described above and
         include it in the answer section.  Go back to step 1.

         If there was no BNAME record, look to see if the "*" label
         exists.

         If the "*" label does not exist, check whether the name we are
         looking for is the original QNAME in the query or a name we
         have followed due to a CNAME.  If the name is original, set an
         authoritative name error in the response and exit.  Otherwise
         just exit.





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         If the "*" label does exist, match RRs at that node against
         QTYPE.  If any match, copy them into the answer section, but
         set the owner of the RR to be QNAME, and not the node with the
         "*" label.  Go to step 6.


   4. Start matching down in the cache.  If QNAME is found in the cache,
      copy all RRs attached to it that match QTYPE into the answer
      section.  If QNAME is not found in the cache but a BNAME record is
      present at QNAME, copy that BNAME record into the
      answer section.  If there was no delegation from authoritative
      data, look for the best one from the cache, and put it in the
      authority section.  Go to step 6.

   5. Use the local resolver or a copy of its algorithm (see resolver
      section of this memo) to answer the query.  Store the results,
      including any intermediate CNAMEs and BNAMEs, in the answer
      section of the response.

   6. Using local data only, attempt to add other RRs which may be
      useful to the additional section of the query.  Exit.



   Note that there will be at most one ancestor with a BNAME as
   described in step 4 unless some zone's data is in violation of the
   no-descendants limitation in section 3.  An implementation might take
   advantage of this limitation by stopping the search of step 3c or
   step 4 when a BNAME record is encountered.


4.2.  Processing by Resolvers

   A resolver or a server providing recursive service must be modified
   to treat a BNAME as somewhat analogous to a CNAME.  The resolver
   algorithm of [RFC1034] section 5.3.3 is modified to renumber step 4.d
   as 4.e and insert a new 4.d.  The complete algorithm becomes:













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   1. See if the answer is in local information, and if so return it to
      the client.

   2. Find the best servers to ask.

   3. Send them queries until one returns a response.

   4. Analyze the response, either:

      a. if the response answers the question or contains a name error,
         cache the data as well as returning it back to the client.

      b. if the response contains a better delegation to other servers,
         cache the delegation information, and go to step 2.

      c. if the response shows a CNAME and that is not the answer
         itself, cache the CNAME, change the SNAME to the canonical name
         in the CNAME RR and go to step 1.

      d. if the response shows a BNAME and that is not the answer
         itself, cache the BNAME.  If substitution of the BNAME's
         <target> for its <owner> in the SNAME would overflow the legal
         size for a <domain-name>, return an implementation-dependent
         error to the application; otherwise perform the substitution
         and go to step 1.

      e. if the response shows a server failure or other bizarre
         contents, delete the server from the SLIST and go back to step
         3.


   A resolver or recursive server which understands BNAME records but
   sends non-extended queries MUST augment step 4.c by deleting from the
   reply any CNAME records which have an <owner> which is a subdomain of
   the <owner> of any BNAME record in the response.


5.  BNAME in DNSSEC

5.1.  BNAME validating

   With the deployment of DNSSEC, more and more servers and resolvers
   will support DNSSEC.  In order to make BNAME valid in DNSSEC
   verification, the DNSSEC enabled resolvers and servers MUST support
   BNAME.  The synthesized CNAME in the answer section for the BNAME
   will never be signed if there has one.

   If the owner name of the bname is the suffix of the name queryed but



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   different, DNSSEC validators MUST understand BNAME, verify the BNAME
   and then checking that the CNAME was properly synthesized in order to
   verify the synthesized CNAME.

   If the owner name of the bname is same with the name queryed, DNSSEC
   validators MUST understand BNAME and verify the BNAME.  The BNAME
   enabled resolver (validator) should do somewhat analogous to a CNAME
   for further query.

   In any negative response, the NSEC or NSEC3 [RFC5155] record type bit
   map SHOULD be checked to see that there was no BNAME that could have
   been applied.  If the BNAME bit in the type bit map is set and the
   query type is not BNAME, then BNAME substitution should have been
   done.

5.2.  BNAME alias algorithm identifiers

   In order to prevent BNAME-unaware resolvers from attempting to
   validate responses from BNAME-signed zones, this specification
   allocates two new DNSKEY algorithm identifiers.  Algorithm Y, DSA-
   BNAME-SHA1 is an alias for algorithm 3, DSA.  Algorithm Z, RSASHA1-
   BNAME-SHA1 is an alias for algorithm 5, RSASHA1.  These are not new
   algorithms, they are additional identifiers for the existing
   algorithms.  Zones signed according to this specification MUST only
   use these algorithm identifiers for their DNSKEY RRs.  The BNAME-
   unaware resolvers will not know these new identifiers and treat
   responses from the BNAME signed zone as insecure, otherwise the bname
   RR will be regarded as bogus if there is no such a mechanism.  These
   algorithm identifiers are used with the BNAME hash algorithm SHA1.
   Using other BNAME hash algorithms requires allocation of a new alias.
   Validating resolvers which follow the BNAME specification MUST
   recognize the new alias algorithm identifier.


6.  IANA Considerations

   IANA is requested to assign the number to XX.  This document updates
   the IANA registry "DNS SECURITY ALGORITHM NUMBERS".  IANA is
   requested to assign the number to Y and Z.

   [[anchor14: Note in draft: before this document goes to WG Last call,
   it is better that we list all DNSSEC algorithms that need to be
   aliased to reflect compatibility with this extension.]]


7.  Security Considerations

   Both ASCII domain name labels and non-ASCII ones have some aliases.



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   We can bundle the domain name labels and their aliases through BNAME
   in the DNS resolutions.  The name labels and their aliases in the
   particular languages are only known by those who know these
   languages.  Those labels may be regarded as different ones by those
   who don't know those languages.  Those who do not know the aliases
   should only use the familar ones.  The applications will not know the
   aliases unless they are properly configured.


8.  Acknowledgements

   Because the BNAME is very similar to DNAME, the authors learn a lot
   from [RFC2672].  Many ideas are from the discussion in the DNSOP and
   DNSEXT mailling list.  Thanks a lot to all in the list.  Many
   important comments and suggestions are contributed by many members of
   the DNSEXT and DNSOP WGs.  The authors especially thanks the
   following ones:Niall O'Reilly, Glen Zorn, Mark Andrews, George
   Barwood,Olafur Gudmundsson, Sun Guonian and Hanfeng for improving
   this document.


9.  Change History

   [[anchor17: RFC Editor: Please remove this section.]]

9.1.  draft-yao-dnsext-bname: Version 00

   o  Bundle DNS Name Redirection

9.2.  draft-yao-dnsext-bname: Version 01

   o  Improve the algorithm
   o  Improve the text

9.3.  draft-yao-dnsext-bname: Version 02

   o  Add the DNSSEC discussion
   o  Improve the text

9.4.  draft-yao-dnsext-bname: Version 03

   o  Update the DNSSEC discussion
   o  Update the IANA consideration


10.  References





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10.1.  Normative References

   [ASCII]    American National Standards Institute (formerly United
              States of America Standards Institute), "USA Code for
              Information Interchange", ANSI X3.4-1968, 1968.

   [EDNS0]    Vixie, P., "Extension Mechanisms for DNS (EDNS0)",
              RFC 2671, August 1999.

   [RFC1034]  Mockapetris, P., "Domain names - concepts and facilities",
              STD 13, RFC 1034, November 1987.

   [RFC1035]  Mockapetris, P., "Domain names - implementation and
              specification", STD 13, RFC 1035, November 1987.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2136]  Vixie, P., Thomson, S., Rekhter, Y., and J. Bound,
              "Dynamic Updates in the Domain Name System (DNS UPDATE)",
              RFC 2136, April 1997.

   [RFC2671]  Vixie, P., "Extension Mechanisms for DNS (EDNS0)",
              RFC 2671, August 1999.

   [RFC2672]  Crawford, M., "Non-Terminal DNS Name Redirection",
              RFC 2672, August 1999.

   [RFC3490]  Faltstrom, P., Hoffman, P., and A. Costello,
              "Internationalizing Domain Names in Applications (IDNA)",
              RFC 3490, March 2003.

   [RFC3597]  Gustafsson, A., "Handling of Unknown DNS Resource Record
              (RR) Types", RFC 3597, September 2003.

   [RFC3629]  Yergeau, F., "UTF-8, a transformation format of ISO
              10646", RFC 3629, November 2003.

   [RFC3743]  Konishi, K., Huang, K., Qian, H., and Y. Ko, "Joint
              Engineering Team (JET) Guidelines for Internationalized
              Domain Names (IDN) Registration and Administration for
              Chinese, Japanese, and Korean", RFC 3743, April 2004.

   [RFC4033]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "DNS Security Introduction and Requirements",
              RFC 4033, March 2005.

   [RFC4034]  Arends, R., Austein, R., Larson, M., Massey, D., and S.



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              Rose, "Resource Records for the DNS Security Extensions",
              RFC 4034, March 2005.

   [RFC4035]  Arends, R., Austein, R., Larson, M., Massey, D., and S.
              Rose, "Protocol Modifications for the DNS Security
              Extensions", RFC 4035, March 2005.

   [RFC5155]  Laurie, B., Sisson, G., Arends, R., and D. Blacka, "DNS
              Security (DNSSEC) Hashed Authenticated Denial of
              Existence", RFC 5155, March 2008.

10.2.  Informative References

   [RFC2672bis]
              Rose, S. and W. Wijngaards, "Update to DNAME Redirection
              in the DNS", Internet-Draft ietf-dnsext-rfc2672bis-dname-
              17.txt, 6 2009.


Authors' Addresses

   Jiankang YAO
   CNNIC
   No.4 South 4th Street, Zhongguancun
   Beijing

   Phone: +86 10 58813007
   Email: yaojk@cnnic.cn


   Xiaodong LEE
   CNNIC
   No.4 South 4th Street, Zhongguancun
   Beijing

   Phone: +86 10 58813020
   Email: lee@cnnic.cn


   Paul Vixie
   Internet Software Consortium
   950 Charter Street
   Redwood City, CA

   Phone: +1 650 779 7001
   Email: vixie@isc.org





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