Progress IE
Progress tones such as ring back and busy tones, and announcements, such as “The number
you have dialed is no longer in service,” are required to successfully signal voice calls.
Progress tones can be generated by the originating, terminating, or intermediate devices.
The indication of in-band tones and announcements is controlled by the progress IE in
ISDN and H.323 networks. The progress IE signals those interworking situations where
in-band tones and announcements must be used.
The indication that tones and announcements are available is signaled by an alerting, call
proceeding, progress, connect, setup acknowledge, or disconnect message containing a
progress indicator (PI) of PI = 1 or 8, which would be sent in the progress description
field in octet 4. A SETUP message of PI = 3 means the switch is indicating to the originating
gateway that in-band messages are expected.
Table 4-7 describes the meanings for various Progress Description field values.
Table 4-7 ISDN Progress Description Field Values
Hex Value Decimal Binary Description
0x01 1 000 0001 Call is not end-to-end ISDN.
0x02 2 000 0010 Destination address is non-ISDN.
0x03 3 000 0011 Origination address is non-ISDN.
0x04 4 000 0100 Call has returned to the ISDN.
0x08 8 000 1000 In-band information or the appropriate pattern is now
available.
0x0A 10 000 1010 Delay in response at the destination interface.