DNS Extensions (DNSEXT) A. Hubert Internet-Draft Netherlabs Computer Consulting BV. Intended status: Standards Track D. Ulevitch Expires: February 18, 2009 EveryDNS August 17, 2008 EDNS Option for performing a data PING draft-hubert-ulevitch-edns-ping-00.txt Status of this Memo By submitting this Internet-Draft, each author represents that any 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 aware will be disclosed, in accordance with Section 6 of BCP 79. 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 February 18, 2009. Hubert & Ulevitch Expires February 18, 2009 [Page 1] Internet-Draft EDNS Option for performing a data PING August 2008 Abstract For various reasons, it may be desireable to ask a remote nameserver to add certain data to the response to a query. This document describes an EDNS option that implements such behaviour. Table of Contents 1. Key words . . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4 3. Protocol . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1. Nameserver Behaviour . . . . . . . . . . . . . . . . . . . 5 3.2. Resolver Behaviour . . . . . . . . . . . . . . . . . . . . 5 3.3. The PING option . . . . . . . . . . . . . . . . . . . . . 5 3.4. Presentation format . . . . . . . . . . . . . . . . . . . 5 4. Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . 6 4.1. Truncation . . . . . . . . . . . . . . . . . . . . . . . . 6 5. Security Considerations . . . . . . . . . . . . . . . . . . . 7 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 8 7. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 9 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10 8.1. Normative References . . . . . . . . . . . . . . . . . . . 10 8.2. Informative References . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 Intellectual Property and Copyright Statements . . . . . . . . . . 12 Hubert & Ulevitch Expires February 18, 2009 [Page 2] Internet-Draft EDNS Option for performing a data PING August 2008 1. Key words 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 [RFC2119]. Hubert & Ulevitch Expires February 18, 2009 [Page 3] Internet-Draft EDNS Option for performing a data PING August 2008 2. Introduction This document describes an EDNS option that can be used to ask a remote nameserver, be it authoritative or a caching resolver, to copy an opaque string from the query to the response. This string can be used to verify proper transmission of DNS questions and responses of various sizes. Additionally, implementations could utilise EDNS PING as a way to enhance the security of DNS over UDP. Hubert & Ulevitch Expires February 18, 2009 [Page 4] Internet-Draft EDNS Option for performing a data PING August 2008 3. Protocol This document uses an EDNS [RFC2671] option to signal that the remote nameserver should copy this option, and its payload, from the query to the response. 3.1. Nameserver Behaviour A name server that understands the PING option and chooses to honor a particular PING request MUST respond by including the opaque payload in a PING option in an EDNS OPT pseudo-RR in the response message. The PING response should be included in addition to the records that would be returned if no PING request were included. 3.2. Resolver Behaviour Resolvers, including stub resolvers, can signal their desire for an EDNS PING response by adding a PING option in an EDNS OPT pseudo-RR in the question message. The resolver is free to choose a length for the opaque payload of the PING option request, but care should be taken not to exceed acceptable DNS packet size limits. 3.3. The PING option The OPTION-CODE for the PING option is 5. The OPTION-DATA for the PING option is an opaque byte string, the semantics of which are deliberately left outside the protocol. 3.4. Presentation format The presentation format of the PING option is left outside the scope of the protocol. It should be observed that the payload of the PING option is completely arbitrary, and need not be null-terminated, and in general will not be. Hubert & Ulevitch Expires February 18, 2009 [Page 5] Internet-Draft EDNS Option for performing a data PING August 2008 4. Discussion The PING option is modeled on ICMP ECHO-REQUEST and ECHO-RESPONSE packets ([RFC0792]), and can in fact be used in a similar manner to verify connectivity. An example of such verification is to determine the maximum response size that arrives unscathed. In addition, a resolver is free to append a PING option to outgoing queries in order to protect itself from accepting false data by requesting a more more clearly marked response. Such a PING-adorned response can clearly be separated from responses sent by third parties. 4.1. Truncation In some cases, adding the PING option to a response message may trigger message truncation. This specification does not change the rules for DNS message truncation in any way, but implementors will need to pay attention to this issue. Implementations claiming conformance to this draft, and which are configured to honor PING requests MUST respond to such requests, and not drop the PING response to prevent truncation. By definition, a resolver that requests PING responses also supports EDNS, so a resolver that requests PING responses can also use the "sender's UDP payload size" field of the OPT pseudo-RR to signal a receive buffer size large enough to make truncation unlikely. Hubert & Ulevitch Expires February 18, 2009 [Page 6] Internet-Draft EDNS Option for performing a data PING August 2008 5. Security Considerations While EDNS PING might be used to enhance the security of query/ response correlation, in and of itself it is not expected to have security implications. Hubert & Ulevitch Expires February 18, 2009 [Page 7] Internet-Draft EDNS Option for performing a data PING August 2008 6. IANA Considerations IANA is expected and requested to reserve option 5 for EDNS PING. Hubert & Ulevitch Expires February 18, 2009 [Page 8] Internet-Draft EDNS Option for performing a data PING August 2008 7. Acknowledgments Donald Eastlake first discussed the concept of DNS cookies ([I-D.eastlake-dnsext-cookies]), which are remarkably similar to EDNS PING requests, but cover a wider scope and have a defined purpose. Most of this document was copied almost verbatim from [RFC5001] which implements a very similar EDNS option, used for very different purposes. Thanks are due to Rob Austein and other contributors to the NSID RFC. Although any mistakes remain our own, the authors gratefully acknowledge the help and contributions of: Peter van Drijk Hubert & Ulevitch Expires February 18, 2009 [Page 9] Internet-Draft EDNS Option for performing a data PING August 2008 8. References 8.1. Normative References [RFC0792] Postel, J., "Internet Control Message Protocol", STD 5, RFC 792, September 1981. [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. [RFC2181] Elz, R. and R. Bush, "Clarifications to the DNS Specification", RFC 2181, July 1997. [RFC2671] Vixie, P., "Extension Mechanisms for DNS (EDNS0)", RFC 2671, August 1999. 8.2. Informative References [I-D.eastlake-dnsext-cookies] 3rd, D., "Domain Name System (DNS) Cookies", draft-eastlake-dnsext-cookies-03 (work in progress), February 2008. [RFC1123] Braden, R., "Requirements for Internet Hosts - Application and Support", STD 3, RFC 1123, October 1989. [RFC4301] Kent, S. and K. Seo, "Security Architecture for the Internet Protocol", RFC 4301, December 2005. [RFC5001] Austein, R., "DNS Name Server Identifier (NSID) Option", RFC 5001, August 2007. Hubert & Ulevitch Expires February 18, 2009 [Page 10] Internet-Draft EDNS Option for performing a data PING August 2008 Authors' Addresses Bert Hubert Netherlabs Computer Consulting BV. Braillelaan 10 Rijswijk (ZH) 2289 CM The Netherlands Email: bert.hubert@netherlabs.nl David Ulevitch EveryDNS PO Box 927941 San Diego, CA 92192-7941 United States of America Email: davidu@everydns.net Hubert & Ulevitch Expires February 18, 2009 [Page 11] Internet-Draft EDNS Option for performing a data PING August 2008 Full Copyright Statement Copyright (C) The IETF Trust (2008). This document is subject to the rights, licenses and restrictions contained in BCP 78, and except as set forth therein, the authors retain all their rights. 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Information on the procedures with respect to rights in RFC documents can be found in BCP 78 and BCP 79. Copies of IPR disclosures made to the IETF Secretariat 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 implementers or users of this specification can be obtained from the IETF on-line IPR repository at http://www.ietf.org/ipr. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights that may cover technology that may be required to implement this standard. Please address the information to the IETF at ietf-ipr@ietf.org. Hubert & Ulevitch Expires February 18, 2009 [Page 12]