Q.931 Information Elements

Information Elements (IEs) must appear in numerically ascending order within ascending codeset order. Not all IEs are valid with all message types. IEs take two formats; one-octet IEs or variable length IEs.

Codesets

The documentation defines four codesets being:

• Codeset 0 -ITU standard (default start codeset)
• Codeset 5 - National specific
• Codeset 6 - Network Specific
• Codeset 7 - User Specific

One-Octet IEs

These IEs are all shift types (escape codes in non-ITU language) between various code sets.

Value	Meaning
0x95	Locking Shift to Codeset 5
0x96	Locking Shift to Codeset 6
0x9D	Non-Locking Shift to Codeset 5
0x9E	Non-Locking Shift to Codeset 6

NOTE: Those of you still awake will have spotted that the top bit (bit 8 in ITU-speak) is always set on single octet IEs.

Variable Length ITU IEs (Codeset 0)

All the IEs shown are in '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	Notes
0x00	Segmented Message
0x04	Bearer	Required bearer service e.g. voice, data etc.
0x08	Cause	Error/termination code/status.
0x0D	Extended Facility
0x14	Call State
0x18	Channel Id	Defines B channel being used.
0x1C	Facility
0x1E	Progress Indication	Information about call in pr0gress.
0x27	Notification Indication
0x2C	Keypad	Dialed digits.
0x32	Information Request
0x34	Signal	Call progress info including
0x38	Feature Activation	one-octet format
0x39	Feature Indication
0x3A	SPID	infamous Service Profile Identification.
0x3B	Endpoint Identifier
0x40	Information Rate	Packet Mode (PMD)
0x43	Transition Delay	Packet Mode (PMD)
0x44	Packet Layer Binary Params	Packet Mode (PMD)
0x45	Packet Layer window Size	Packet Mode (PMD)
0x46	Packet Size	Packet Mode (PMD)
0x4C	Connected Number	If a disconnect during CONFERENCE indicates the remaining caller.
0x6C	Calling Party Number	Who is calling
0x6D	Calling Party Subaddress
0x70	Called Party Number	Who we are calling.
0x71	Called Party subaddress
0x74	Redirecting Number
0x76	Redirection Number
0x78	Transit Network Selection
0x79	Restart Indicator
0x7C	LLC	Lower Layer Compatability
0x7D	HLC	Higher Layer Compatability
0x7E	User-User	User-User Information

National Specific IEs (Codeset 5)

Since these message types are National they are listed under the country/region. These IE's are preceded with a locking (0x95) or non-locking (0x9D) shift to codeset 5.

North America - NI-1, 2 and 3

Value	Name	Notes
0x01	Operator System Access	Only in originating SETUP (User-Network)
0x2A	Display Text	Formatted text for display

Network Specific IEs (Codeset 6)

Since these message types are typically proprietary or National they are listed under the vendor (or country) value. These IE's are preceded with a locking (0x96) or non-locking (0x9E) shift to codeset 6.

North America - NI-1, 2 and 3

Value	Name	Notes
0x3E	Protocol Version Control
0x41	Closed User Group
0x42	Reverse Charging Indication
0x75	Redirecting Subaddress
0x7B	Call Appearance	Call Appearance number being used (Key system IE)

CUSTOM LUCENT

Value	Name	Notes
0x02	User Code	Provides authorization info for calls (voice or data)
0x21	Associated Type	Provides call status for key systems
0x22	Selected Call appearance	Network says use this call appearance
0x23	Origination Call Appearance	The call appearance we are using for this call
0x25	Destination Call Appearance	On incoming call - should be same as last SCA
0x26	Endpoint Identifier
0x32	Keypad Control
0x36	Switch hook	0 = on-hook, 1 = off-hook
0x37	Other Call Reference	Used in CONFerence operations
0x38	Feature Activation	two-octet format
0x39	Feature Indication
0x3A	Adjunct Control
0x3B	Display Control
0x3C	Display Field	5ESS is very verbose
0x7A	Management	used in MAN_INFO message types

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