Symbol |
Time-out
value |
Cause for initiation |
Normal termination |
At expiry |
| T1 |
15-60 seconds |
When release message is sent |
At the receipt of Release complete message |
Retransmit release message and start timer T1 |
| T2 |
3 minutes |
When controlling exchange receives suspend (user) message |
At receipt of resume (user) message at controlling exchange |
Initiate release procedure |
| T3 |
2 minutes |
At receipt of overload message |
On expiry |
Initiate release procedure |
| T4 |
5-15 minutes |
At receipt of MTP-STATUS primitive with the cause "inaccessible
remote user " |
On expiry, or at receipt of user part available message (or any other) |
Send user part test message. Start T4 |
| T5 |
5-15 minutes |
When initial release message is sent |
At receipt of release complete message |
Send reset circuit message, alert maintenance personnel and remove the
circuit from service, stop T1, start T17. Procedure continues until maintenance
intervention occurs |
| T6 |
Covered in Rec. Q.118 |
When controlling exchange receives suspend (network) |
At receipt of resume (network) message or release message |
Initiate release procedure |
| T7 |
20-30 seconds |
When the latest address message is sent |
When the condition for normal release of address and routing information
is met (receipt of ACM, CON messages) |
Release all equipment and connection (send release message) |
| T8 |
10-15 seconds |
When an exchange receives Initial address message requiring continuity
check on this circuit or indicates that continuity check has been performed on a previous
circuit |
At receipt of continuity message |
Release all equipment and connection into the network (send release
message) |
| T9 |
Interval specified in Rec. Q.118 |
When national controlling or outgoing international exchange receives ACM |
At the receipt of answer |
Release connection send back release message |
| T10 |
4-6 seconds |
When last digit is received in interworking situations |
At the receipt of fresh information |
Send address complete message |
| T11 |
15-20 seconds |
When latest address message is received in interworking situations |
When ACM is sent |
Send address complete message |
| T12 |
15-60 seconds |
When blocking message is sent |
At receipt of blocking acknowledgement |
Retransmit blocking message and start T12 |
| T13 |
5-15 minutes |
When initial blocking message is sent |
At receipt of blocking acknowledgement |
Transmit blocking message and alert maintenance personnel, start T13,
stop T12. Procedure continues until maintenance intervention occurs |
| T14 |
15-60 seconds |
When unblocking message is sent |
At receipt of unblocking acknowledgement |
Retransmit unblocking message and start T14 |
| T15 |
5-15 minutes |
When initial unblocking message is sent |
At receipt of unblocking acknowledgement |
Retransmit unblocking message alert maintenance personnel, start T15 and
stop T14. Procedure continues until maintenance intervention occurs |
| T16 |
15-60 seconds |
When reset circuit message is sent not due to expiry of T5 |
At the receipt of the acknowledgement (RLC message) |
Retransmit reset circuit message and start T16 |
| T17 |
5-15 minutes |
When initial reset circuit message is sent |
At the receipt of the acknowledgement |
Alert maintenance personnel, retransmit reset circuit message, start T17,
stop T16. Procedure continues until maintenance intervention occurs |
| T18 |
15-60 seconds |
When group blocking message is sent |
At receipt of group blocking acknowledgement |
Retransmit group blocking message and start T18 |
| T19 |
5-15 minutes |
When initial group blocking message is sent |
At receipt of group blocking acknowledgement |
Retransmit group blocking message, alert maintenance personnel, start
T19, stop T18. Procedure continues until maintenance intervention occurs |
| T20 |
15-60 seconds |
When group unblocking message is sent |
At receipt of group unblocking acknowledgement |
Retransmit group unblocking message and start T20 |
| T21 |
5-15 minutes |
When initial group unblocking message is sent |
At receipt of group unblocking acknowledgement |
Retransmit group unblocking message, alert maintenance personnel, start
T21, stop T20. Procedure continues until maintenance intervention occurs |
| T22 |
15-60 seconds |
When circuit group reset message is sent |
At receipt of the acknowledgement |
Retransmit circuit group reset message and start T22 |
| T23 |
5-15 minutes |
When initial circuit group reset message is sent |
At the receipt of the acknowledgement |
Alert maintenance personnel and start T23, retransmit circuit group reset
message, stop T22. Procedure continues until maintenance intervention occurs |
| T24 |
< 2 seconds |
When check tone is sent |
At the receipt of the backward check tone |
Send continuity message with failure indication and:
a) start T25 if continuity check was asked in IAM and make automatic repeat attempt, or
b) start T24 if continuity check was asked in CCR
|
| T25 |
1-10 seconds |
When initial continuity check failure is detected |
– |
Send CCR message and repeat continuity check |
| T26 |
1-3 minutes |
When second or subsequent continuity check failure is detected |
– |
Send CCR message and repeat continuity check |
| T27 |
4 minutes |
When continuity check failure is received |
At receipt of continuity check request message |
Send reset circuit message, start T16 and T17 |
| T28 |
10 seconds |
When send CQM |
At receipt of CQR |
Alert maintenance |
| T29 |
300-600 ms |
Congestion indication received when T29 not running |
– |
New congestion indication will be taken into account |
| T30 |
5-10 seconds |
Congestion indication received when T29 not running |
– |
Restore traffic by one step if not yet at full load and start T30 |
| T31 |
> 6 minutes |
Release of ISDN User part signalling connection based on CO SCCP |
On expiry |
Call reference reusable |
| T32 |
3-5 seconds |
When response to request of end-to-end connection establishment is sent |
At receipt of first end-to-end message from the remote end |
End-to-end message allowed to be sent |
| T33 |
12-15 seconds |
When send INR |
On receipt of INF |
Release call, alert maintenance personnel |
| T34 |
2-4 seconds |
When indication of a segmented message is received on an IAM, ACM, CPG,
ANM or CON message |
At receipt of a segmentation message |
Proceed with call |
| T35 |
15-20 seconds |
At receipt of the latest digit (< >ST) and before the minimum or
fixed number of digits have been received |
At receipt of ST or when the minimum or fixed number of digits have been
received |
Send release message (cause 28) |
| T36 |
10-15 seconds |
When transit or incoming international exchange receives continuity check
request message |
At receipt of continuity or release message |
Release all equipment , send reset circuit message, start T16 and T17 |
| T37 – reserved for ISUP'92 |
2-4 seconds |
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| T38 |
Interval specified in Rec. Q.118 |
When the incoming international exchange sends to the preceding exchange
a suspend (network) message |
At receipt of resume (network) or release message |
Send release message (cause 102) |
| T39 |
Interval specified in Rec. Q.730 |
When a MCID request is sent |
At receipt of a MCID response |
Call continues |
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