One document matched: draft-jennings-sip-dtls-05.txt
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Network Working Group C. Jennings
Internet-Draft Cisco Systems
Intended status: Standards Track N. Modadugu
Expires: April 12, 2008 Google, Inc.
October 10, 2007
Session Initiation Protocol (SIP) over Datagram Transport Layer Security
(DTLS)
draft-jennings-sip-dtls-05
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Copyright Notice
Copyright (C) The IETF Trust (2007).
Abstract
This specification defines how to use Datagram Transport Layer
Security (DTLS) as a transport for Session Initiation Protocol (SIP).
DTLS is a protocol for providing Transport Layer Security (TLS)
security over a datagram protocol. This specification also specifies
the IANA registrations for using SIP with Datagram Congestion Control
Protocol (DCCP). DTLS can be used with either UDP or the Datagram
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Congestion Control Protocol (DCCP). To accommodate this, this
specification also defines how to use SIP directly over DCCP.
1. Introduction
Datagram Transport Layer Security (DTLS) [2] provides communication
privacy similar to TLS [9] for datagram packets. SIP can run over
both stream and datagram transports, including UDP and TCP. SIP [4]
already defines how to use TLS with stream oriented transports. This
specification extends SIP to use DTLS with datagram oriented
transports. Since DTLS can be used with either UDP or the Datagram
Congestion Control Protocol (DCCP) as the underlying transport this
specification also defines the usage of SIP directly over DCCP.
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 [5].
3. VIA Codes
Via header fields in SIP carry a transport protocol identifier. This
specification extends RFC 3261 to define the value "DTLS-UDP" for
DTLS over UDP[2] and "DTLS-DCCP" for DTLS over DCCP[1] and "DCCP" for
directly over DCCP[8]. The update to the ABNF[3] in RFC 3261 for
this parameter is the following:
transport =/ "DCCP" / "DTLS-DCCP" / "DTLS-UDP"
The following is an example Via header field:
Via: SIP/2.0/DTLS-UDP atlanta.example.com:5060
4. DTLS and DCCP Usage
The normal rules for sending a request over UDP in RFC 3261 apply to
sending over DTLS and directly over DCCP. Note that the congestion
safety rules for UDP do not apply to DTLS over DCCP and 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.
Note that DCCP performs Path Maximum Transfer Unit (PMTU) discovery.
Implementations of SIP over DTLS over DCCP and SIP over DCCP MUST use
the PMTU discovered by DCCP when determining the maximum request size
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for the connection.
4.1. DCCP Option Usage
The following considerations regarding the usage of DCCP options and
features apply to the DCCP connections for DTLS and SIP directly over
DCCP:
o Congestion Control ID (CCID) negotiation for both directions of
the connection MUST include CCID 2 (TCP-like congestion control).
CCID 2 optimizes for throughput over smooth rate changes and
should be suitable for SIP applications. Applications MAY choose
to include other CCIDs, in any preference order.
o Connections MUST NOT use the Minimum Checksum Coverage Feature.
5. Locating DTLS SIP Servers
The normal rules from RFC 3263 [6] apply when locating a SIP server
that supports DTLS. The following new NAPTR[7] service values are
defined: "SIPS+D2U" for UDP, and "SIPS+D2D" for DCCP[8]. In
addition, the service value "SIP+D2D" should be used for SIP without
DTLS directly over DCCP.
The default port for DTLS over UDP or DCCP is 5061. The default port
for SIP directly over DCCP is 5060.
6. Security Considerations
The security issues with SIP using DTLS are equivalent to the issues
of using SIP with TLS. All the security considerations in RFC 3261
relevant to TLS apply to DTLS.
SIP over DCCP presents the same security issues as SIP over UDP, with
the exception that DCCP enforces congestion control at the transport
layer.
7. IANA Considerations
This document defines new NAPTR service field values for DTLS over
DCCP and UDP as well as over DCCP with no DTLS. IANA is requested to
register these values under the "Registry for the SIP SRV Resource
Record Services Field". The resulting entries should be:
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Services Field Protocol Reference
-------------------- -------- ---------
SIPS+D2U UDP [RFCXXXX]
SIPS+D2D DCCP [RFCXXXX]
SIP+D2D DCCP [RFCXXXX]
[Note to RFC Editor: Please replace XXXX with the RFC number of this
specification.]
This document registers two new DCCP Service Codes registry as
defined by RFC 4340.
Service Code ASCII Description Reference
------------ ----- ---------------------------------- ---------
1936289824 sip SIP over DCCP [RFCXXXX]
1936289907 sips SIP over DCCP over DTLS [RFCXXXX]
This document defines to new ports in the DCCP Port Numbers Registry
as defined by RFC 4340.
Port Name Port Number Description Reference
-------------- ------------- ------------------------- ---------
sip-dccp 5060/dccp SIP over DCCP [RFCXXXX]
sip-dtls-dccp 5061/dccp SIP over DTLS over DCCP [RFCXXXX]
8. Acknowledgments
Much of text and outline for this specification came from RFC 4168
authored by Jonathan Rosenberg, Henning Schulzrinne, and Gonzalo
Camarillo. Jakob Schlyter caught several typos. Eric Rescorla
provided helpful comments and text. Tom Phelan provided much of the
DCCP text. Thanks also to Colin Perkins.
9. References
9.1. Normative References
[1] Phelan, T., "Datagram Transport Layer Security (DTLS) over the
Datagram Congestion Control Protocol (DCCP)",
draft-ietf-dccp-dtls (work in progress).
[2] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security", RFC 4347, April 2006.
[3] Crocker, D. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 4234, October 2005.
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[4] 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.
[5] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[6] Rosenberg, J. and H. Schulzrinne, "Session Initiation Protocol
(SIP): Locating SIP Servers", RFC 3263, June 2002.
[7] Mealling, M., "Dynamic Delegation Discovery System (DDDS) Part
Three: The Domain Name System (DNS) Database", RFC 3403,
October 2002.
[8] Kohler, E., Handley, M., and S. Floyd, "Datagram Congestion
Control Protocol (DCCP)", RFC 4340, March 2006.
9.2. Informative References
[9] Dierks, T. and E. Rescorla, "The Transport Layer Security (TLS)
Protocol Version 1.1", RFC 4346, April 2006.
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
Google, Inc.
1600 Ampitheatre Parkway
Muntain View, CA 94043
USA
Email: ngm@google.com
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