DTLS-SRTP Handling in SIP Back-to-Back User Agents
RFC 7879
Internet Engineering Task Force (IETF) R. Ravindranath
Request for Comments: 7879 T. Reddy
Category: Standards Track G. Salgueiro
ISSN: 2070-1721 Cisco
V. Pascual
Oracle
P. Ravindran
Nokia Networks
May 2016
DTLS-SRTP Handling in SIP Back-to-Back User Agents
Abstract
Session Initiation Protocol (SIP) Back-to-Back User Agents (B2BUAs)
exist on the signaling and media paths between the endpoints. This
document describes the behavior of B2BUAs when Secure Real-time
Transport (SRTP) security context is set up with the Datagram
Transport Layer Security (DTLS) protocol.
Status of This Memo
This is an Internet Standards Track document.
This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7879.
Ravindranath, et al. Standards Track [Page 1]
RFC 7879 DTLS-SRTP Handling in SIP B2BUA May 2016
Copyright Notice
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Overview . . . . . . . . . . . . . . . . . . . . . . . . 3
1.2. Goals and Scope of this Document . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. B2BUAs Procedures to Allow End-to-End DTLS-SRTP . . . . . . . 5
4. Signaling-Plane B2BUA Handling of DTLS-SRTP . . . . . . . . . 5
4.1. Proxy-B2BUAs . . . . . . . . . . . . . . . . . . . . . . 6
4.2. Signaling-Only and SDP-Modifying Signaling-Only B2BUAs . 6
5. Media-Plane B2BUA Handling of DTLS-SRTP . . . . . . . . . . . 6
5.1. General . . . . . . . . . . . . . . . . . . . . . . . . . 6
5.1.1. Media Relay . . . . . . . . . . . . . . . . . . . . . 6
5.1.2. RTP- and RTCP-Aware Media-Aware B2BUA . . . . . . . . 8
6. Forking Considerations . . . . . . . . . . . . . . . . . . . 9
7. Security Considerations . . . . . . . . . . . . . . . . . . . 10
8. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
8.1. Normative References . . . . . . . . . . . . . . . . . . 11
8.2. Informative References . . . . . . . . . . . . . . . . . 11
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 12
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
Ravindranath, et al. Standards Track [Page 2]
RFC 7879 DTLS-SRTP Handling in SIP B2BUA May 2016
1. Introduction
1.1. Overview
[RFC5763] describes how the Session Initiation Protocol (SIP)
[RFC3261] can be used to establish a Secure Real-time Transport
Protocol (SRTP) [RFC3711] security context with the Datagram
Transport Layer Security (DTLS) protocol [RFC6347]. It describes a
mechanism for transporting a certificate fingerprint using the
Session Description Protocol (SDP) [RFC4566]. The fingerprint
identifies the certificate that will be presented during the DTLS
handshake. DTLS-SRTP is currently defined for point-to-point media
sessions, in which there are exactly two participants. Each DTLS-
SRTP session (described in Section 3 of [RFC5764]) contains a single
DTLS connection (if RTP and RTP Control Protocol (RTCP) are
multiplexed) or two DTLS connections (if RTP and RTCP are not
multiplexed), and either two SRTP contexts (if media traffic is
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