The PINX at the destination interface may, optionally, include any of the specific private network Progress description values in the ALERTING, PROGRESS or CONNECT message returned to the public network, to enable notification of particular situations at the destination side. The public network shall then transfer the information as follows:
– a Transit PINX shall transfer the information elements to the preceding PINX;
– a Relay Node shall transfer the information elements to the preceding PINX;
– an Incoming Gateway PINX may transfer the information to the other network;
– an Originating PINX may convey the information to the calling user.
Incoming Gateway PINX functionality shall provide Progress indicator information elements in the SETUP message as specified below, and this information shall be transferred to the physical PINX. If none of the specified conditions apply, no Progress indicator information element shall be included.
If one of the following progress descriptions has been received on a call entering the CN, that information shall be passed on:
– No. 1 – Call is not end-to-end ISDN, further call progress information may be available inband.
– No. 3 – Origination address is non-ISDN.
If the call has entered the Corporate Network from a network (public or private) which is not ISDN, a Progress indicator information element may be sent containing progress description No. 1, Call is not end-to-end ISDN; further call progress information may be available in-band.
When the public network receives a specific private network Progress description value from the preceding PINX, it shall transfer it to the physical PINX at the destination interface, without acting upon it.
Up to three Progress indicator information elements may be included in a SETUP, ALERTING, PROGRESS and CONNECT message.