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Command Reference Guide
Global Configuration Mode Command Set
ip sip grammar require 100rel
Use the ip sip grammar require 100rel command to add 100rel to the Require header of a Session
Initiation Protocol (SIP) provisional response. Use the no form of this command to return to the default
setting.
Syntax Description
No subcommands.
Default Values
By default, ip sip grammar require 100rel is disabled.
Command History
Release 15.1
Command was introduced.
Functional Notes
This command enables or disables the sending of reliable provisional responses to clients that support
100rel. Reliable provisional responses will always be sent to clients that require 100rel even with ip sip
grammar require 100rel disabled.
Usage Examples
The following example enables ip sip grammar require 100rel:
(config)#ip sip grammar require 100rel
Technology Review
There are two Require headers that may use the 100rel tag, one in the initial request, and one in the
provisional response.
The user agent client (UAC) is used to initiate SIP requests. When the UAC creates a new request, it can
require reliable provisional responses for that request by adding the option tag 100rel to the Require
header of that request.
The user agent server (UAS) contacts the user when SIP requests are received, and returns responses on
behalf of the user, using provisional responses for request progress information. Provisional responses
(100 to 199) are transmitted on a best-effort basis. By using reliable provisional responses, responses are
sent by the UAS until they are acknowledged as received. This is especially beneficial when sending
provisional responses over an unreliable transport, such as User Datagram Protocol (UDP).
The UAS must send any non-100 provisional responses reliably if the initial request contained a Require
header field with the option tag 100rel. If the UAS is unwilling to do so, it must reject the initial request with
a Bad Extension message and include an Unsupported header field containing the option tag 100rel. If the
client supports 100rel, the UAS has the option of sending provisional responses with or without the
Require 100rel tag as instructed by the ip sip grammar require 100rel command.
60000CRG0-35E
Copyright © 2012 ADTRAN, Inc.
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