Dialogic 6.2 manual Interpreting Information Elements, Hex Message, November 107

BSMI Debugging

Table 3. Q.931 Message Types (Continued)

Message Type Bits								Hex	Message
0	1	1	1	1	0	1	1	7B	Information
0	1	1	0	1	1	1	0	6E	Notify
0	1	1	1	1	1	0	1	7D	Status
0	1	1	1	0	1	0	1	75	Status Enquiry

Interpreting Information Elements

For Q.931 call control messages, the first Information Element (IE) starts at byte offset 9 in the hexadecimal string. Each message can contain several IEs of either fixed (single byte) or variable length.

03 278D Xmit 00 60 0 Setup 00 00 0 0018

00C10000080101050 4028890 180181 2C0735353532303030

IEs

Figure 8 on page 108 compares the general IE format against the first IE contained in the example SETUP message, and illustrates the following points:

„A value of 0 in the shaded bit position indicates a variable-length IE; a value of 1 in that position indicates a single byte IE.

Note: Single byte IEs are commonly used for locking codeset shifts. Locking shift IEs appear only after all variable-length IEs within the message. Refer to the Bellcore Technical Reference TR-TSY-000268 for more information on the structure and use of single byte IEs and codeset shifts.

„The IE identifier value 0x04 indicates a Bearer Capability IE; refer to Table 4 on page 108 for possible IE identifier values. IEs appear in messages in ascending order according to their identifier number.

„The 2-byte length of the IE value indicates that it contains only the required structures for a Bearer Capability IE.

„The IE contents indicate an information transfer capability of unrestricted digital information (0x88) and a transfer rate/mode equal to 64 kbps/circuit mode (0x90).

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