ISDN Messages
ISDN signaling is carried out by messages that are sent between endpoints on the D
channel. The Message Type is a single byte (octet) that indicates what type of message is
being sent or received. Four general categories of messages might be present: Call
Establishment, Call Information, Call Clearing, and Miscellaneous. Generally, the most
useful messages to understand are the Call Establishment and Call Clearing messages. The
most common messages are listed in Table 4-5.
Table 4-5 ISDN Messages
Message Type Binary Value Message Name
000 Call Establishment 00001 ALERTing
00010 CALL PROCeeding
00011 PROGress
00101 SETUP
00111 CONNect
01101 SETUP ACKnowledge
01111 CONNect ACKnowledge
001 Call Information 00000 USER INFOrmation
00001 SUSPend REJect
00010 RESume REJect
00101 SUSPend
00110 RESume
01101 SUSPend ACKnowledge
01110 RESume ACKnowledge
010 Call Clearing 00101 DISConnect
00110 Restart
01101 RELease
01110 Restart ACKnowledge
11010 RELease COMplete
Table 4-5 ISDN Messages (continued)
Message Type Binary Value Message Name
011 Miscellaneous 00000 SEGment
00010 FACility
01110 NOTIFY
10101 STATUS ENQuiry
11001 Congestion Control
11011 INFOrmation
11101 STATUS
Table 4-6 provides a list of message types and the IEs that can be associated with each
message.