DNS Extensions Working Group G. Barwood Internet-Draft Intended status: Standards Track 20 September 2009 Expires: March 2010 DNS Transport Signal draft-barwood-dnsext-dns-transport-signal-00 Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and 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 March 19, 2010. Copyright Notice Copyright (c) 2009 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 in effect on the date of publication of this document (http://trustee.ietf.org/license-info). Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Abstract Describes a DNS resource record that is used to signal support for DNS transport protocols. Barwood Expires March 2010 [Page 1] Internet-Draft DNS Transport Signal September 2009 1. Introduction DNS clients are currently unable to efficiently determine which transport protocols a DNS server supports. A DNS client may try each protocol in turn, but this is an undesirable waste of resources and time, especially as multiple probes have to be sent to take account of packet loss. Even for the current protocols, TCP and UDP, a client may prefer to use TCP for security reasons, but may not be willing to wait for the TCP connection to fail where the server does not support TCP. It is expected that new optional transport protocols may be added in future, for example a protocol which combines the best features of TCP and UDP. Therefore a new resource record type, TPORT is proposed. 2. TPORT Resource record format The RDATA wire format is a list of 8-bit numbers that identify DNS transport protocols. The RDATA presentation format is a list of protocol mnenomics. If the mnemonic is not known, PROTOCOL may be used where is the number of the protocol. Example: NS1.EXAMPLE.NET. 3600 TPORT UDP TCP 3. Protocol The TPORT record for a domain is added to the Additional Section of a DNS response whenever an A or AAAA record for the domain is sent. In particular, a parent zone with a glue A or AAAA record may also have a glue TPORT record. If the parent zone does not support the TPORT record, or there is no facility for the domain owner to upload a TPORT record to the parent zone, the method described in Appendix A may be used instead. 4. Security Considerations TBD Barwood Expires March 2010 [Page 2] Internet-Draft DNS Transport Signal September 2009 5. IANA Considerations The TPORT resource record type, with a sub-registry for DNS transport protocols, initialized to TCP 1 [RFC1035] UDP 2 [RFC1035] 6. Acknowledgments TBD 7. Normative References [RFC1035] Mockapetris, P., "Domain names - implementation and specification", STD 13, RFC 1035, November 1987. Appendix A. Name server name encoding It may take some time for the TPORT record to be universally supported. In the interim period, TPORT information may be encoded into a name server name. The convention is that the name server name contains a label starting with 'TPORT-', followed by a list of one or more protocol mnemomics separated by '-'. For example EXAMPLE.COM 3600 NS TPORT-TCP-UDP.NS1.EXAMPLE.NET. indicates that the name server for EXAMPLE.COM has support for TCP and UDP. Author's Address George Barwood 33 Sandpiper Close Gloucester GL2 4LZ United Kingdom Phone: +44 452 722670 EMail: george.barwood@blueyonder.co.uk Barwood Expires March 2010 [Page 3]