SIP timer summary
RFC 3261, "SIP: Session Initiation Protocol" specifies various timers that SIP uses.
Timer Default value Section Meaning T1 500 ms 17.1.1.1 Round-trip time (RTT) estimate T2 4 sec. 17.1.2.2 Maximum retransmission interval for non-INVITE requests and INVITE responses T4 5 sec. 17.1.2.2 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 Timer C > 3 min. 16.6 bullet 11 Proxy INVITE transaction timeout Timer D > 32 sec. for UDP 17.1.1.2 Wait time for response retransmissions 0 sec. for TCP and SCTP Timer E initially T1 17.1.2.2 Non-INVITE request retransmission interval, UDP only Timer F 64*T1 17.1.2.2 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 Timer I T4 for UDP 17.2.1 Wait time for ACK retransmissions 0 sec. for TCP and SCTP Timer J 64*T1 for UDP 17.2.2 Wait time for retransmissions of non-INVITE requests 0 sec. for TCP and SCTP Timer K T4 for UDP 17.1.2.2 Wait time for response retransmissions 0 sec. for TCP and SCTP
Related tasks
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Configure SIP timers
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