Reference
(subclause)

Call establishment messages:

ALERTING

3.3.1

CALL PROCEEDING

3.3.2

CONNECT

3.3.4

CONNECT ACKNOWLEDGE

3.3.5

SETUP

3.3.9

SETUP ACKNOWLEDGE

3.3.10

Call information phase messages:

USER INFORMATION

3.3.13

Call clearing messages:

RELEASE

3.3.7

RELEASE COMPLETE

3.3.8

Miscellaneous messages:

CONGESTION CONTROL

3.3.3

INFORMATION

3.3.6

STATUS

3.3.11

STATUS ENQUIRY

3.3.12

Note - In Recommendation Q.931 (1988), support of user-user signalling was included for a number of reasons, including support of additional compatibility checking upon bilateral agreement with other users or in accordance with other standards (e.g. Recommendation X.213 [23]). To utilise this capability, the User-user information element can be included in the ALERTING, CONNECT, RELEASE, RELEASE COMPLETE and SETUP messages. Details on this capability (explicit and implicit Type 1 user-user signalling) are given in Recommendation Q.957 [54].