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
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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.
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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
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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
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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]
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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.
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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
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