Archive for the ‘Q.931’ tag
Progress Indicators (PIs) in ISDN Q.931
According to Bellcore and ANSI specifications, in-band progress tones and announcements are required for PSTN services and for ISDN speech and 3.1-kHz voice services. In order to guarantee that the necessary in-band tones are generated when required (and at the right switch), Cisco H.323 gateways must ensure that Progress Indicators or PIs are carried end-to-end in called signaling messages between the calling and called parties. The PI is an IE that signals when in-band tones and announcements are available. The PI is configured by the "progress_ind" command. Below is a list of PIs that can be configured on a Cisco H.323 gateway:
Configurable Progress Indicator Values for H.323 Gateways
- PI=0 No progress indicator is included. Message type: Setup
- PI=1 Call is not end-to-end ISDN; further call progress information may be available in-band. Message type: Alert, setup, progress, connect
- PI=2 Destination address is non-ISDN Message type: Alert, progress, connect
- PI=3 Origination address is non-ISDN Message type: Setup
- PI=8 In-band information or appropriate pattern is now available Message type: Alert, progress, connect
