Archive for the ‘ISDN’ 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
ISDN Overlap Receiving
Overlap receiving allows the matching of dial peers as the digits are being entered. I’m not aware of the benefits of ISDN overlap receiving, but it does exist and we need to be prepared for it on the voice lab. Without overlap receiving, digits presented to available dial peers are sent en bloc, meaning that 5123 is analyzed as “5123″ and not “5″ … “1″ … “2″ … “3″
