Figures II.8 through II.16 show example conditions when cause mappings would be utilized between Q.931 and X.25messages and utilize the specific mappings of Table 6-5 and Table 6-6 as shown below.
Figure Reference Table
Q.931 failures during call establishment
User side failures during X.25 data transfer phase
Figure II.13 Table 6-5 (Note1)
Figure II.14 Table 6-5 (Note2)
Network side premature clearing
NOTES
1. This mapping is only needed in the case of the Q.931 message arriving prior to the clearing of the last virtual call.
2. This situation always results in either an X.25 clear indication packet with cause No. 9, out of order for switched virtual calls, or an X.25 reset packet with cause No. 9,out of order for permanent virtual circuits.
Figure II.1/Q.931 – Example message sequence for the ISDN virtual circuit service B-channel access – First virtual call set-up in this channel
Figure II.2/Q.931 – Example message sequence for the ISDN virtual circuit service B-channel access – Last virtual call cleared in this channel
Figure II.3/Q.931 – Example message sequence for the ISDN virtual circuit service D-channel access – First virtual call set-up in this SAPI = 16 link
Figure II.4/Q.931 – Example message sequence for the ISDN virtual circuit service D-channel access – Last virtual call cleared in this SAPI = 16 link
Figure II.5/Q.931 – Example of incoming call offering procedures using signalling on SAPI = 0 link – Terminal accepts call on a new B-channel
Figure II.6/Q.931 – Example of incoming call offering procedures using signalling on SAPI = 0 link – Terminal accepts call on a established B-channel
Figure II.7/Q.931 – Example of incoming call offering procedures using signalling on SAPI = 0 link – Terminal accepts call on the D-channel
Figure II.8/Q.931 – Undeliverable call
Figure II.9/Q.931 – Erroneous message (e.g. format error)
Figure II.10/Q.931 – No responding user
Figure II.11/Q.931 – Expiry of timer T301
Figure II.12/Q.931 – Call rejection by called party
Figure II.13/Q.931 – Q.931 clearing during X.25 data transfer phase
Figure II.14/Q.931 – Q.931 RESTART during X.25 data transfer phase
Figure II.15/Q.931 – Premature clearing of the virtual call (e.g. expiry of X.25 timer T21)
Figure II.16/Q.931 – Premature clearing of the virtual call
