The Stream Control Transmission Protocol (SCTP) as a Transport for the Session Initiation Protocol (SIP)
RFC 4168
| Document | Type |
RFC - Proposed Standard
(October 2005; No errata)
Was draft-ietf-sip-sctp (sip WG)
|
|
|---|---|---|---|
| Last updated | 2015-10-14 | ||
| Stream | IETF | ||
| Formats | plain text pdf html bibtex | ||
| Stream | WG state | (None) | |
| Document shepherd | No shepherd assigned | ||
| IESG | IESG state | RFC 4168 (Proposed Standard) | |
| Consensus Boilerplate | Unknown | ||
| Telechat date | |||
| Responsible AD | Allison Mankin | ||
| Send notices to | <rohan@cisco.com> | ||
Network Working Group J. Rosenberg
Request for Comments: 4168 Cisco Systems
Category: Standards Track H. Schulzrinne
Columbia University
G. Camarillo
Ericsson
October 2005
The Stream Control Transmission Protocol (SCTP)
as a Transport for the Session Initiation Protocol (SIP)
Status of This Memo
This document specifies an Internet standards track protocol for the
Internet community, and requests discussion and suggestions for
improvements. Please refer to the current edition of the "Internet
Official Protocol Standards" (STD 1) for the standardization state
and status of this protocol. Distribution of this memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (2005).
Abstract
This document specifies a mechanism for usage of SCTP (the Stream
Control Transmission Protocol) as the transport mechanism between SIP
(Session Initiation Protocol) entities. SCTP is a new protocol that
provides several features that may prove beneficial for transport
between SIP entities that exchange a large amount of messages,
including gateways and proxies. As SIP is transport-independent,
support of SCTP is a relatively straightforward process, nearly
identical to support for TCP.
Rosenberg, et al. Standards Track [Page 1]
RFC 4168 SCTP as a Transport for SIP October 2005
Table of Contents
1. Introduction ....................................................2
2. Terminology .....................................................2
3. Potential Benefits ..............................................2
3.1. Advantages over UDP ........................................3
3.2. Advantages over TCP ........................................3
4. Transport Parameter .............................................5
5. SCTP Usage ......................................................5
5.1. Mapping of SIP Transactions into SCTP Streams ..............5
6. Locating a SIP Server ...........................................6
7. Security Considerations .........................................7
8. IANA Considerations .............................................7
9. References ......................................................7
9.1. Normative References .......................................7
9.2. Informative References .....................................8
1. Introduction
The Stream Control Transmission Protocol (SCTP) [4] has been designed
as a new transport protocol for the Internet (or intranets) at the
same layer as TCP and UDP. SCTP has been designed with the transport
of legacy SS7 signaling messages in mind. We have observed that many
of the features designed to support transport of such signaling are
also useful for the transport of SIP (the Session Initiation
Protocol) [5], which is used to initiate and manage interactive
sessions on the Internet.
SIP itself is transport-independent, and can run over any reliable or
unreliable message or stream transport. However, procedures are only
defined for transport over UDP and TCP. This document defines
transport of SIP over SCTP.
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 [1].
3. Potential Benefits
RFC 3257 presents some of the key benefits of SCTP [10]. We
summarize some of these benefits here and analyze how they relate to
SIP (a more detailed analysis can be found in [12]).
Rosenberg, et al. Standards Track [Page 2]
RFC 4168 SCTP as a Transport for SIP October 2005
3.1. Advantages over UDP
All the advantages that SCTP has over UDP regarding SIP transport are
also shared by TCP. Below, there is a list of the general advantages
that a connection-oriented transport protocol such as TCP or SCTP has
over a connection-less transport protocol such as UDP.
Fast Retransmit: SCTP can quickly determine the loss of a packet,
because of its usage of SACK and a mechanism that sends SACK
messages faster than normal when losses are detected. The result
is that losses of SIP messages can be detected much faster than
when SIP is run over UDP (detection will take at least 500 ms, if
not more). Note that TCP SACK exists as well, and TCP also has a
fast retransmit option. Over an existing connection, this results
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