SIP C. Jennings Internet-Draft Cisco Systems Expires: August 13, 2005 N. Modadugu Stanford University February 12, 2005 Using DTLS as a Transport for SIP draft-jennings-sip-dtls-00 Status of this Memo This document is an Internet-Draft and is subject to all provisions of section 3 of RFC 3667. 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 become aware will be disclosed, in accordance with RFC 3668. 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 13, 2005. Copyright Notice Copyright (C) The Internet Society (2005). Abstract This draft specifies how to use Datagram Transport Layer Security (DTLS) as a transport for SIP. DTLS is a new protocol for providing TLS security over a datagram protocol. This draft is being discussed on the sip@ietf.org mailing list. Jennings & Modadugu Expires August 13, 2005 [Page 1] Internet-Draft DTLS Transport for SIP February 2005 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Transport Parameters . . . . . . . . . . . . . . . . . . . . . 3 4. DTLS Usage . . . . . . . . . . . . . . . . . . . . . . . . . . 4 5. Locating DTLS SIP Servers . . . . . . . . . . . . . . . . . . 4 6. Security Considerations . . . . . . . . . . . . . . . . . . . 4 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5 9. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5 9.1 Normative References . . . . . . . . . . . . . . . . . . . . 5 9.2 Informational References . . . . . . . . . . . . . . . . . . 5 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 6 Intellectual Property and Copyright Statements . . . . . . . . 7 Jennings & Modadugu Expires August 13, 2005 [Page 2] Internet-Draft DTLS Transport for SIP February 2005 1. Introduction Datagram Transport Layer Security (DTLS) [7] provides communication privacy similar to TLS for datagram packets. SIP can run over both stream and datagram transports. SIP already defines how to use TLS with stream oriented transports. This specification extends SIP to use DTLS with datagram oriented transports. 2. Terminology 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 RFC 2119 [3]. 3. Transport Parameters SIP URIs can carry a transport parameter indicating the transport protocol to be used. This specification defines two new values for the transport parameter: "dtls-udp" for the SIP URI transport parameter to be used for messages sent using DTLS over UDP, and "dtls-dccp" for messages sent using DTLS over DCCP. The update to the ABNF in RFC 3261 for this parameter is the following: transport-param = "transport=" ( "udp" / "tcp" / "sctp" / "tls" / "tls-sctp" "dtls-dccp" / "dtls-udp" / other-transport) The following is an example of SIP URIs using "dtls-udp": sip:alice@example.com;transport=dtls-udp Via header fields also carry a transport protocol identifier. This specification extends RFC 3261 to define the value "DTLS-UDP" for DTLS over UDP and "DTLS-DCCP" for DTLS over DCCP. The update to the ABNF in RFC 3261 for this parameter is the following: transport = "UDP" / "TCP" / "TLS" / "SCTP" / "TLS-SCTP" "DTLS-DCCP" / "DTLS-UDP" / other-transport The following is an example Via header field: Via: SIP/2.0/DTLS-UDP atlanta.example.com:5060 Jennings & Modadugu Expires August 13, 2005 [Page 3] Internet-Draft DTLS Transport for SIP February 2005 4. DTLS Usage The normal rules for sending a request over UDP in RFC 3261 apply to sending over DTLS. Note that the congestion safety rules for UDP do not apply to DCCP. In addition, the normal rules for validating a TLS connection in RFC 3261 apply to DTLS connections. Requests with a sips URI can be sent over DTLS as well as TLS. 5. Locating DTLS SIP Servers The normal rules from RFC 3263 [4] apply when locating a SIP server that supports DTLS. The following new NAPTER[5] service values are defined: "SIPS+D2U" for UDP, and "SIPS+D2D" for DCCP. In addition, "SIP+D2D" should be used for SIP without DTLS over DCCP. The default port for DTLS over UDP is 5061. 6. Security Considerations The security issues with SIP using DTLS are closely equivalent to the issues of using SIP with TLS. All the security considerations in RFC 3261 relevant to TLS apply to DTLS. 7. IANA Considerations The IANA is requested to update the following entry to the "SIP/SIPS URI Parameters" registry. The reference to this RFC should appear in double-brackets and be appended to the list of references already listed on for the transport parameter, as indicated in RFC 3969 [6]. The resulting entry should be similar to: Parameter Name Predefined Values Reference -------------- ----------------- --------- transport Yes [RFC3261] [[RFCXXXX]] This document also defines new NAPTR service field values. The IANA is requested to register these values under the "Registry for the SIP SRV Resource Record Services Field". The resulting entries should be: Services Field Protocol Reference -------------------- -------- --------- SIPS+D2U UDP [RFCXXXX] SIPS+D2D DCCP [RFCXXXX] SIP+D2D DCCP [RFCXXXX] Jennings & Modadugu Expires August 13, 2005 [Page 4] Internet-Draft DTLS Transport for SIP February 2005 8. Acknowledgments Much of text and outline for this specification came from [8] authored by Jonathan Rosenberg, Henning Schulzrinne, and Gonzalo Camarillo. 9. References 9.1 Normative References [1] Rescorla, E., "Datagram Transport Layer Security", draft-rescorla-dtls-02 (work in progress), December 2004. [2] Rosenberg, J., Schulzrinne, H., Camarillo, G., Johnston, A., Peterson, J., Sparks, R., Handley, M. and E. Schooler, "SIP: Session Initiation Protocol", RFC 3261, June 2002. [3] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [4] Rosenberg, J. and H. Schulzrinne, "Session Initiation Protocol (SIP): Locating SIP Servers", RFC 3263, June 2002. [5] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part Three: The Domain Name System (DNS) Database", RFC 3403, October 2002. 9.2 Informational References [6] Camarillo, G., "The Internet Assigned Number Authority (IANA) Uniform Resource Identifier (URI) Parameter Registry for the Session Initiation Protocol (SIP)", BCP 99, RFC 3969, December 2004. [7] Kohler, E., "Datagram Congestion Control Protocol (DCCP)", draft-ietf-dccp-spec-09 (work in progress), November 2004. [8] Rosenberg, J., "The Stream Control Transmission Protocol (SCTP) as a Transport for the Session Initiation Protocol (SIP)", draft-ietf-sip-sctp-06 (work in progress), February 2005. Jennings & Modadugu Expires August 13, 2005 [Page 5] Internet-Draft DTLS Transport for SIP February 2005 Authors' Addresses Cullen Jennings Cisco Systems 170 West Tasman Drive MS: SJC-21/2 San Jose, CA 95134 USA Phone: +1 408 902-3341 EMail: fluffy@cisco.com Nagendra Modadugu Stanford University 353 Serra Mall Stanford, CA 94305 USA EMail: Nagendra@cs.stanford.edu Jennings & Modadugu Expires August 13, 2005 [Page 6] Internet-Draft DTLS Transport for SIP February 2005 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any Intellectual Property Rights 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; nor does it represent that it has made any independent effort to identify any such rights. 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Disclaimer of Validity This document and the information contained herein are provided on an "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Copyright Statement Copyright (C) The Internet Society (2005). 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. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Jennings & Modadugu Expires August 13, 2005 [Page 7]