SIP Timers

Created by Kelly Evans, Modified on Fri, 31 Jan at 11:10 AM by Kelly Evans

Section 17 of RFC 3261 defines several SIP Timers

17 Transactions

17.1 Client Transaction

17.1.1  INVITE Client Transaction

17.1.1.1  Overview of INVITE Transaction

17.1.1.2 Formal Description

17.1.1.3 Construction of the ACK Request

17.1.2 Non-INVITE Client Transaction

17.1.2.1 Overview of the non-INVITE Transaction

17.1.2.2 Formal Description

17.1.3 Matching Responses to Client Transactions

17.1.4 Handling Transport Errors

17.2 Server Transaction

17.2.1 INVITE Server Transaction

17.2.2 Non-INVITE Server Transaction

17.2.3 Matching Requests to Server Transactions

17.2.4 Handling Transport Errors

This table is a Summary of SIP Timers that are defined in Section 17 of RFC 3261 and used by the Peeredge Orchestrator.

Timer
Default value
Section
Meaning
Timer
Default value
Section
Meaning
T1
500 ms
17.1.1.1
Round-trip time (RTT) estimate
T2
4 sec
17.1.1.2
Maximum retransmission interval for non-INVITE requests and INVITE responses
T4
5 sec
17.1.1.2
Maximum duration that a message can remain in the network
Timer A
initially T1
17.1.1.2
INVITE request retransmission interval, for UDP only
Timer B
64*T1
17.1.1.2
INVITE transaction timeout timer for INVITE transaction
Timer D
>32 sec for UDP
0 sec for TCP/TLS
17.1.1.2
Wait time for response retransmissions for INVITE transaction
Timer E
initially T1
17.1.1.2
Non-INVITE request retransmission interval, UDP only
Timer F
64*T1
17.1.1.2
Non-INVITE transaction timeout timer
Timer G
initially T1
17.2.1
INVITE response retransmission interval
Timer H
64*T1
17.2.1
Wait time for ACK receipt for INVITE transaction
Timer I
T4 for UDP
0 sec for TCP/TLS
17.2.1
Wait time for ACK retransmissions
Timer J
64*T1 for UDP
0 sec
17.2.2
Wait time for retransmissions of non-INVITE requests
Timer K
T4 for UDP
0 sec for TCP/TLS
17.2.2.1
Wait time for response retransmissions

Timer	Default value	Section	Meaning
T1	500 ms	17.1.1.1	Round-trip time (RTT) estimate
T2	4 sec	17.1.1.2	Maximum retransmission interval for non-INVITE requests and INVITE responses
T4	5 sec	17.1.1.2	Maximum duration that a message can remain in the network
Timer A	initially T1	17.1.1.2	INVITE request retransmission interval, for UDP only
Timer B	64*T1	17.1.1.2	INVITE transaction timeout timer for INVITE transaction
Timer D	>32 sec for UDP 0 sec for TCP/TLS	17.1.1.2	Wait time for response retransmissions for INVITE transaction
Timer E	initially T1	17.1.1.2	Non-INVITE request retransmission interval, UDP only
Timer F	64*T1	17.1.1.2	Non-INVITE transaction timeout timer
Timer G	initially T1	17.2.1	INVITE response retransmission interval
Timer H	64*T1	17.2.1	Wait time for ACK receipt for INVITE transaction
Timer I	T4 for UDP 0 sec for TCP/TLS	17.2.1	Wait time for ACK retransmissions
Timer J	64*T1 for UDP 0 sec	17.2.2	Wait time for retransmissions of non-INVITE requests
Timer K	T4 for UDP 0 sec for TCP/TLS	17.2.2.1	Wait time for response retransmissions