Yealink SIP-T21 E2 Administrator's Guide

Configuring Basic Features
435
Parameters
Permitted Values
Default
Description:
Configures the SIP session timer of T4 (in seconds).
T4 represents the maximum duration a message will remain in the network.
Web User Interface:
Settings->SIP->SIP Session Timer T4 (2.5~60s)
Phone User Interface:
None
To configure session timer via web user interface:
1. Click on Settings->SIP.
2. Enter the desired value in the SIP Session Timer T1 (0.5~10s) field.
3. Enter the desired value in the SIP Session Timer T2 (2~40s) field.
4. Enter the desired value in the SIP Session Timer T4 (2.5~60s) field.
5. Click Confirm to accept the change.
Session Timer
Session timer allows a periodic refresh of SIP sessions through an UPDATE request, to
determine whether a SIP session is still active. Session timer is specified in RFC 4028. IP phones
support two refresher modes: UAC and UAS. Whether the endpoint functions as a UAC or a
UAS depends on the UA that initiates the SIP request. If the initiator is configured as UAC, the
other client or the SIP server will function as a UAS. If the initiator is configured as UAS, the
other client or the SIP server will function as a UAC. The session expiration is negotiated via the
Session-Expires header in the INVITE message. The negotiated refresher is always the UAC and

Yealink SIP-T21 E2 Specifications

General

Brand	Yealink
Model	SIP-T21 E2
Category	IP Phone
Language	English