The following table provides a summary of the MTP3 messages included in this
page:
| Octet 1: |
field |
| bits 4-1 |
Service Indicator (bits DCBA) |
| bits 8-5 |
Sub-service field which contains the network indicator (bits
DC) and two spare bits (bits BA) |
| DCBA |
Service Indicator |
| 0 0 0 0 |
SNMM: Signalling Network Management Messages |
| 0 0 0 1 |
SNTM: Signalling Network Testing and Maintenance Messages |
| 0 0 1 0 |
Spare |
| 0 0 1 1 |
SCCP: Signalling Connection Control Part |
| 0 1 0 0 |
TUP: Telephone User Part |
| 0 1 0 1 |
ISUP: ISDN User Part |
| 0 1 1 0 |
DUPC: Data User Part (call and circuit related messages) |
| 0 1 1 1 |
DUPR: Data User Part (facility registration and cancellation
messages) |
| 1 0 0 0 |
Reserved for MTP Testing User Part |
| DC |
Sub-service field |
| 0 0 |
International Network |
| 0 1 |
Spare (Reserved for national use) |
| 1 0 |
National Network |
| 1 1 |
Reserved for national use |
The standard routing label has a length of 32 bits and is placed at the
beginning of the Signalling Information Field of a MSU:
The following timers have been defined. The ranges are given
below. The values, in brackets, are the minimum values for use when routes with
long propagation delays are used (e.g. routes including satellite sections).
|
Timer |
Value |
Designation |
| T1 |
500 (800) to 1200 ms. |
Delay to avoid message mis-sequencing on
changeover. |
| T2 |
700 (1400) to 2000 ms |
Waiting for changeover acknowledgement |
| T3 |
500 (800) to 1200 ms. |
Time controlled diversion-delay to avoid mis-sequencing
on changeback |
| T4 |
500 (800) to 1200 ms |
Waiting for changeback acknowledgement (first
attempt). |
| T5 |
500 (800) to 1200 ms |
Waiting for changeback acknowledgement (second
attempt). |
| T6 |
500 (800) to 1200 ms |
Delay to avoid message mis-sequencing on
controlled rerouting. |
| T7 |
1 to 2 seconds. |
Waiting for signalling data link connection
acknowledgement. |
| T8 |
800 to 1200 ms. |
Transfer prohibited inhibition timer
(transient solution). |
| T9 |
|
Not used. |
| T10 |
30 to 60 seconds. |
Waiting to repeat signalling route set test
message
The maximum value may be extended at the discretion of the management
function in certain situations, e.g. many signalling points being
unavailable or signalling point of known long term unavailability. |
| T11 |
30 to 90 seconds |
Transfer restricted timer. (This is one way of
implementing the function described in 13.4 and mainly intended to
simplify STPs.) |
| T12 |
800 to 1500 ms. |
Waiting for uninhibit acknowledgement. |
| T13 |
800 to 1500 ms |
Waiting for force uninhibit. |
| T14 |
2 to 3 seconds. |
Waiting for inhibition acknowledgement |
| T15 |
2 to 3 seconds. |
Waiting to start signalling route set
congestion test. |
| T16 |
1.4 to 2 seconds. |
Waiting for route set congestion status
update. |
| T17 |
800 to 1500 ms. |
Delay to avoid oscillation of initial
alignment failure and link restart. |
| T18 |
|
Timer within a signalling point whose MTP
restarts for supervising link and link set activation as well as the
receipt of routing information. The value is implementation and network
dependent.Criteria to choose T18 are given in 9.2 |
| T19 |
67 to 69 seconds |
Supervision timer during MTP restart to avoid
possible ping-pong of TFP, TFR and TRA messages. |
| T20 |
59 to 61 seconds. |
Overall MTP restart timer at the signalling
point whose MTP restarts. |
| T21 |
63 to 65 seconds. |
Overall MTP restart timer at a signalling
point adjacent to one whose MTP restarts. |
| T22 |
3 to 6 minutes (provisional value) |
Local inhibit test timer. |
| T23 |
3 to 6 minutes (provisional value). |
Remote inhibit test timer. |
| T24 |
500 ms (provisional value). |
Stabilising timer after removal of local
processor outage, used in LPO latching to RPO (national option) |
