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)
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Authors | Henning Schulzrinne , Jonathan Rosenberg , Gonzalo Camarillo | ||
Last updated | 2015-10-14 | ||
Stream | IETF | ||
Formats | plain text html pdf htmlized 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 resultsShow full document text