Reference
(subclauses)

Call establishment messages:

ALERTING

3.1.1

CALL PROCEEDING

3.1.2

CONNECT

3.1.3

CONNECT ACKNOWLEDGE

3.1.4

PROGRESS

3.1.8

SETUP

3.1.14

SETUP ACKNOWLEDGE

3.1.15

Call information phase messages:

RESUME

3.1.11

RESUME ACKNOWLEDGE

3.1.12

RESUME REJECT

3.1.13

SUSPEND

3.1.18

SUSPEND ACKNOWLEDGE

3.1.19

SUSPEND REJECT

3.1.20

Call clearing messages:

DISCONNECT

3.1.5

RELEASE

3.1.9

RELEASE COMPLETE

3.1.10

Miscellaneous messages:

INFORMATION

3.1.6

NOTIFY

3.1.7

STATUS

3.1.16

STATUS ENQUIRY

3.1.17

Note - In Recommendation Q.931 (1988) [53], 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 utilize this capability, the User-user information element can be included in the ALERTING, CONNECT, DISCONNECT, PROGRESS, 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].