Network Working Group R. Austein Internet-Draft ISC Expires: August 9, 2004 February 9, 2004 EDNS NSID Extension draft-austein-dnsext-nsid-00 Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. 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." The list of current Internet-Drafts can be accessed at http:// www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on August 9, 2004. Copyright Notice Copyright (C) The Internet Society (2004). All Rights Reserved. Abstract With the increased use of DNS anycast, load balancing, and other mechanisms allowing more than one DNS name server to share a single IP address, it is sometimes difficult to tell which of a pool of name servers has answered a particular query. While existing ad-hoc mechanism allow an operator to send follow-up queries when it is necessary to debug such a configuration, the only completely reliable way to obtain the identity of the name server which actually responded is to have the name server include this information in the response itself. This note proposes a protocol enhancement to support this functionality. Austein Expires August 9, 2004 [Page 1] Internet-Draft EDNS NSID Extension February 2004 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Proposed Mechanism . . . . . . . . . . . . . . . . . . . . . . 4 2.1 The SI Flag . . . . . . . . . . . . . . . . . . . . . . . . . 4 2.2 The NSID Option . . . . . . . . . . . . . . . . . . . . . . . 4 3. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1 What Should the NSID Payload Be? . . . . . . . . . . . . . . . 5 3.2 Should Recursive Name Servers Respond to SI? . . . . . . . . . 5 4. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 7 Normative References . . . . . . . . . . . . . . . . . . . . . 8 Informative References . . . . . . . . . . . . . . . . . . . . 9 Author's Address . . . . . . . . . . . . . . . . . . . . . . . 9 Intellectual Property and Copyright Statements . . . . . . . . 10 Austein Expires August 9, 2004 [Page 2] Internet-Draft EDNS NSID Extension February 2004 1. Introduction With the increased use of DNS anycast, load balancing, and other mechanisms allowing more than one DNS name server to share a single IP address, it is sometimes difficult to tell which of a pool of name servers has answered a particular query. Existing ad-hoc mechanisms such as those described in [I-D.ietf-dnsop-serverid] allow an operator to send follow-up queries when it is necessary to debug such a configuration, but there are situations in which this is not a totally satisfactory solution, since anycast routing may have changed, or the server pool in question may be behind some kind of extremely dynamic load balancing hardware. Thus, while these ad-hoc mechanisms are certainly better than nothing (and have the advantage of already being deployed), a better solution seems desirable. Given that a DNS query is an idempotent operation with no retained state, it would appear that the only completely reliable way to obtain the identity of the name server which actually responded to a particular query is to have that name server include identifying information in the response itself. This note proposes a protocol enhancement to achieve this. Austein Expires August 9, 2004 [Page 3] Internet-Draft EDNS NSID Extension February 2004 2. Proposed Mechanism This note proposes using an EDNS [RFC2671] flag bit to signal the resolver's desire for information identifying the name server, and an EDNS option to hold the name server's response (should it chose to honor the resolver's request). 2.1 The SI Flag A resolver signals its desire for information identifying the server by setting the SI (Send Identification) flag in the extended flags field of the OPT pseudo-RR. The value of the SI flag is [TBD]. The semantics of the SI flag are not transitive. That is: the SI flag is a request that the name server which receives the query identify itself; in a so-called forwarding setup, the first hop name server is the one that should identify itself. If the resolver side of a forwarding name server wishes to receive identifying information, it is free to set the SI flag in its own queries, but that is a separate matter. A name server which understands the SI flag should echo its value back in the response message, regardless of whether the name server chose to honor the request. 2.2 The NSID Option A name server which understands the SI flag and chooses to honor it responds by including identifying information in a NSID option in an EDNS OPT pseudo-RR in the response message. The OPTION-CODE for the NSID option is [TBD]. The precise format of the identifying information is still an open issue at this point, and is discussed further in Section 3.1. Austein Expires August 9, 2004 [Page 4] Internet-Draft EDNS NSID Extension February 2004 3. Open Issues There are a couple of open issues in this proposal which would need to be settled before it could be used. The author has opinions on both of these and has stated those opinions below, but would appreciate feedback from the community. 3.1 What Should the NSID Payload Be? There are several options for the payload of the NSID option. It could be the "real" name of the specific name server within the name server pool. It could be the "real" IP address (IPv4 or IPv6) of the name server within the name server pool. It could be some sort of hash of the DNS name or IP address, perhaps including some kind of nonce. It could be an arbitrary string of octets chosen at the discretion of the name server operator. Each of these options has advantages and disadvantages. Using the "real" name or "real" address is simple, but assumes that the name server has a "real" name (it probably does have at least one non-anycast IP address, for maintenance operations). Using the "real" IP address assumes that the operator of an anycast name server is willing to divulge a non-anycast address for the name server, which might not be the case. Using a hash (with or without a nonce) provides a fixed length value that the resolver can use to tell two name servers apart without necessarily being able to tell where either one of them "really" is, but makes debugging more difficult if one happens to be in a friendly open environment. Using an arbitrary octet string means that at least half of the name servers that support this option will probably end up identifying themselves as "My Name Server", which is not particularly useful. Given that one of the reasons for using anycast DNS techniques is often an attempt to harden a critical name server against denial of service attacks, the author believes that the hash with nonce option is probably the right choice here, since it will provide enough information for useful debugging without leaking the maintenance address of anycast name servers to nogoodniks. 3.2 Should Recursive Name Servers Respond to SI? Most of the discussion of name server identification to date has Austein Expires August 9, 2004 [Page 5] Internet-Draft EDNS NSID Extension February 2004 focused on identifying authoritative name servers, since the best known cases of anycast name servers are a subset of the name servers for the root zone. However, given that anycast DNS techniques are equally applicable to recursive name servers as well as authoritative name servers, it may be useful for the name server side of a recursive name server to support this mechanism as well. The semantics proposed for the SI bit in Section 2.1 are intended to support this model. Austein Expires August 9, 2004 [Page 6] Internet-Draft EDNS NSID Extension February 2004 4. Acknowledgements David Conrad, Paul Vixie, Randy Bush, Suzanne Woolf, and the law firm of Dewey, Chetham, and Howe. Austein Expires August 9, 2004 [Page 7] Internet-Draft EDNS NSID Extension February 2004 Normative References [RFC2671] Vixie, P., "Extension Mechanisms for DNS (EDNS0)", RFC 2671, August 1999. Austein Expires August 9, 2004 [Page 8] Internet-Draft EDNS NSID Extension February 2004 Informative References [I-D.ietf-dnsop-serverid] Conrad, D., "Identifying an Authoritative Name Server", draft-ietf-dnsop-serverid-01 (work in progress), November 2002. Author's Address Rob Austein ISC 950 Charter Street Redwood City, CA 94063 USA EMail: sra@isc.org Austein Expires August 9, 2004 [Page 9] Internet-Draft EDNS NSID Extension February 2004 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. Copies of claims of rights made available for publication and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementors or users of this specification can be obtained from the IETF Secretariat. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights which may cover technology that may be required to practice this standard. Please address the information to the IETF Executive Director. Full Copyright Statement Copyright (C) The Internet Society (2004). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assignees. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION Austein Expires August 9, 2004 [Page 10] Internet-Draft EDNS NSID Extension February 2004 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Acknowledgement Funding for the RFC Editor function is currently provided by the Internet Society. Austein Expires August 9, 2004 [Page 11]