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Tech Stuff - Q.931 Message Types

Message Types may take two formats; a one-octet ITU standard or a two-octet Network Specific (which is sometimes a euphemism for proprietary).

Two-Octet Format

This message type is preceeded by an escape octet = 0.

8 7 6 5 4 3 2 1
0 0 0 0 0 0 0 0
Message Type

Message Types

All the message types shown are as 'C' type hexadecimal values rather than the more normal bit format of ITU documentation - for our ease of use. You are welcome to convert them back to binary if that is easier to work with!!

Standard ITU one-octet messages

Value Name Direction
0x01 ALERTing Both
0x02 CALL PROCeeding Both
0x03 PROGress Network->User
0x05 SETUP Both
0x07 CONNect Both
0x0D SETUP ACKnowledge Network->User
0x0F CONNect ACKnowledge Both
0x24 HOLD Both
0x28 HOLD ACKnowledge Both
0x30 HOLD REJect Both
0x31 RETrieve Both
0x33 RETrieve ACKnowledge Both
0x37 RETrieve REJect Both
0x45 DISConnect Both
0x4D RELease Both
0x5A RELease COMplete Both
0x60 SEGment Network->User
0x62 FACility Both
0x64 REGister User->Network
0x75 STATUS ENQuiry Network->User
0x7B INFOrmation Both
0x7D STATUS User->Network
0x7E NOTIFY Network->User

Network Specific two-octet messages

Since these message types are typically proprietary or National they are listed under the vendor (or country) value. For the sake of brevity the preceding zero (see above) has been omitted.

National ISDN-1, 2, 3 (North America)

Value Name Direction
0xFB KEY HOLD Network->User
0xFC KEY RELease Network->User
0xFF KEY SETUP Network->User
0xFE KEY SETUP ACKnowledge User->Network

CUSTOM LUCENT

Value Name Direction
0x90 CONFerence User->Network
0x91 CONFerence ACKnowledge Network->User
0x92 CONFerence REJect Network->User
0x93 TRANSfer User->Network
0x94 TRANSfer ACKnowledge Network->User
0x95 TRANSfer REJect Network->User
0x96 ASSOCiated Network->User
0x97 ASSOCiated ACKnowledge User->Netwok
0x98 DROP User->Network
0x99 DROP ACKnowledge Network->User
0x9A DROP REJect Network->User
0x9B HOLD User->Network
0x9C HOLD ACKnowledge Network->User
0x9D HOLD REJect Network->User
0x9E RECONNect User->Network
0x9CF RECONNect ACKnowledge Network->User
0xB0 RECONNect REJect Network->User
0xB1 REDIRect Network->User
0xF7 MANagement INFOrmation Both


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