Connection Reuse in the Session Initiation Protocol (SIP)
RFC 5923
Internet Engineering Task Force (IETF) V. Gurbani, Ed.
Request for Comments: 5923 Bell Laboratories, Alcatel-Lucent
Category: Standards Track R. Mahy
ISSN: 2070-1721 Unaffiliated
B. Tate
BroadSoft
June 2010
Connection Reuse in the Session Initiation Protocol (SIP)
Abstract
This document enables a pair of communicating proxies to reuse a
congestion-controlled connection between themselves for sending
requests in the forwards and backwards direction. Because the
connection is essentially aliased for requests going in the backwards
direction, reuse is predicated upon both the communicating endpoints
authenticating themselves using X.509 certificates through Transport
Layer Security (TLS). For this reason, we only consider connection
reuse for TLS over TCP and TLS over Stream Control Transmission
Protocol (SCTP). This document also provides guidelines on
connection reuse and virtual SIP servers and the interaction of
connection reuse and DNS SRV lookups in SIP.
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 5741.
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/rfc5923.
Gurbani, et al. Standards Track [Page 1]
RFC 5923 SIP Connection Reuse June 2010
Copyright Notice
Copyright (c) 2010 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
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Table of Contents
1. Introduction ...................................................3
2. Terminology ....................................................4
3. Applicability Statement ........................................5
4. Benefits of TLS Connection Reuse ...............................5
5. Overview of Operation ..........................................6
6. Requirements ..................................................10
7. Formal Syntax .................................................11
8. Normative Behavior ............................................11
8.1. Client Behavior ...........................................11
8.2. Server Behavior ...........................................13
8.3. Closing a TLS Connection ..................................14
9. Security Considerations .......................................14
9.1. Authenticating TLS Connections: Client View ...............14
9.2. Authenticating TLS Connections: Server View ...............15
9.3. Connection Reuse and Virtual Servers ......................15
10. Connection Reuse and SRV Interaction ..........................17
11. IANA Considerations ...........................................17
12. Acknowledgments ...............................................17
13. References ....................................................18
13.1. Normative References ......................................18
13.2. Informative References ....................................18
Gurbani, et al. Standards Track [Page 2]
RFC 5923 SIP Connection Reuse June 2010
1. Introduction
SIP entities can communicate using either unreliable/connectionless
(e.g., UDP) or reliable/connection-oriented (e.g., TCP, SCTP
[RFC4960]) transport protocols. When SIP entities use a connection-
oriented protocol (such as TCP or SCTP) to send a request, they
typically originate their connections from an ephemeral port.
In the following example, A listens for SIP requests over TLS on TCP
port 5061 (the default port for SIP over TLS over TCP), but uses an
ephemeral port (port 49160) for a new connection to B. These
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