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//usr/share/doc/bind-9.8.2/draft/draft-yao-dnsext-bname-04.txt
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 Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- 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. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must include Simplified BSD License text as described in Section 4.e of Yao, et al. Expires February 12, 2011 [Page 1] Internet-Draft bname August 2010 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 material may not have granted the IETF Trust the right to allow modifications of such material outside the IETF Standards Process. Without obtaining an adequate license from the person(s) controlling the copyright in such materials, this document may not be modified outside the IETF Standards Process, and derivative works of it may not be created outside the IETF Standards Process, except to format 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 Yao, et al. Expires February 12, 2011 [Page 2] Internet-Draft bname August 2010 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 Yao, et al. Expires February 12, 2011 [Page 3] Internet-Draft bname August 2010 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 Yao, et al. Expires February 12, 2011 [Page 4] Internet-Draft bname August 2010 [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 Yao, et al. Expires February 12, 2011 [Page 5] Internet-Draft bname August 2010 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: Yao, et al. Expires February 12, 2011 [Page 6] Internet-Draft bname August 2010 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. Yao, et al. Expires February 12, 2011 [Page 7] Internet-Draft bname August 2010 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: Yao, et al. Expires February 12, 2011 [Page 8] Internet-Draft bname August 2010 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 Yao, et al. Expires February 12, 2011 [Page 9] Internet-Draft bname August 2010 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. Yao, et al. Expires February 12, 2011 [Page 10] Internet-Draft bname August 2010 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 Yao, et al. Expires February 12, 2011 [Page 11] Internet-Draft bname August 2010 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. Yao, et al. Expires February 12, 2011 [Page 12] Internet-Draft bname August 2010 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 Yao, et al. Expires February 12, 2011 [Page 13]
