Yealink SIP-T41P Configuration Manual page 23

Timer T1
Timer T1 is an estimate of the Round Trip Time (RTT) of transactions between a SIP client
and SIP server.
Timer T2
Timer T2 represents the maximum retransmitting time of any SIP request message. The
re-transmitting and doubling of T1 will continue until the retransmitting time reaches the
T2 value.
Example:
The user registers a SIP account for the IP phone and then set the value of Timer T1,
Timer T2 respectively (Timer T1: 0.5, Timer T2: 4). The SIP registration request message
will be re-transmitted between the IP phone and SIP server. The re-transmiting and
doubling of Timer T1 (0.5) will continue until the retransmitting time reaches the Timer T2
(4). The total registration request retry time will be less than 64 times of T1 (64 * 0.5 = 32).
The re-transmitting interval in sequence is: 0.5s, 1s, 2s, 4s, 4s, 4s, 4s, 4s, 4s and 4s.
Timer T4
Timer T4 represents the time the network will take to clear messages between the SIP
client and server.
To configure SIP session timer via CommPortal phone configurator:
1. Click on Preference->SIP.
2. Enter the desired value in the SIP Session Timer T1 field.
The valid value is 0.5-10s, and the default value is 0.5s.
3. Enter the desired value in the SIP Session Timer T2 field.
The valid value is 2-40s, and the default value is 4s.
4. Enter the desired value in the SIP Session Timer T4 field.
The valid value is 2.5-60s, and the default value is 5s.
Customizing Your Phone
15