Tech Info - 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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