Signaling System No. 7 (SS7/C7): Protocol, Architecture, and Services

Appendix H. ISUP Timers for ANSI/ETSI/ITU-T Applications

This appendix lists all ISUP timers. The timer values are specified in ITU-T Q.764 [78]. ETSI ISUP timers [18] are identical to ITU-T timers.

Timers applicable to the US network are specified in ANSI T1.113-2000 [3].

Table H-1. ISUP Timers Specified in ANSI, ETSI and ITU-T

Timer	Duration Before Time-Out	Starts	Normal Termination	Action at Time-Out
min = minute(s) sec = seconds(s) ms = millisecond(s)
T1	15–60 sec (ITU) 4–15 sec (ANSI)	When Release Message is sent	Upon receipt of Release Complete Message	Retransmit Release Message and start timer T1
T2 (ITU-T ONLY)	3 min	When controlling exchange receives Suspend (User) Message	Upon receipt of Resume (User) Message, at controlling exchange	Initiate release ...