cc/td/doc/product/software/ios122/rel_docs
hometocprevnextglossaryfeedbacksearchhelp
PDF

Table of Contents

SIP Messages and Methods Overview

SIP Messages and Methods Overview

This chapter provides a brief overview of SIP messages and methods. This chapter contains information about the following:

Format

All SIP messages are either requests from a server or client or responses to a request. The messages are formatted according to RFC 822, "Standard for the format of ARPA internet text messages." For all messages, the general format is:

Each line must end with a carriage return-line feed (CRLF).

Requests

SIP uses six types (methods) of requests:

Responses

The following types of responses are used by SIP and generated by the Cisco SIP Proxy Server:

The Registration Process

A registration occurs when a client needs to inform a proxy or redirect server of its location. During this process, the client sends a REGISTER request to the proxy or redirect server and includes the address (or addresses) at which it can be reached.

The Invitation Process

An invitation occurs when one SIP end point (user A) "invites" another SIP endpoint (user B) to join in a call. During this process, user A sends an INVITE message requesting that user B join a particular conference or establish a two-party conversation. If user B wants to join the call, it sends an affirmative response (SIP 2xx). Otherwise, it sends a failure response (SIP 4xx). Upon receiving the response, user A acknowledges the response with an ACK message. If user A no longer wants to establish this conference, it sends a BYE message instead of an ACK message.

SIP is a new protocol developed by the Internet Engineering Task Force (IETF) Multiparty Multimedia Session Control (MMUSIC) Working Group as an alternative to the ITU-T H.323 specification. SIP is defined by RFC 2543 and is used for multimedia call session setup and control over IP networks.


hometocprevnextglossaryfeedbacksearchhelp
Posted: Wed Sep 11 14:04:58 PDT 2002
All contents are Copyright © 1992--2002 Cisco Systems, Inc. All rights reserved.
Important Notices and Privacy Statement.