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4-6 Message structure and function
preference to other information (for example, destination number, number
plan identification, and so forth); checks are made to ensure that the call
setup information is consistent with the network facilities requested for the
call.
Notification Indicator
The Notification Indicator information element indicates or conveys
information pertaining to a call.
Original Called Number
The Original Called Number information element identifies the number
from which the first redirection/diversion was invoked. Optionally, this
information element may be passed from user to user without network
interpretation or interaction. The Original Called Number information
element is Northern Telecom proprietary to support cross-product
interworking and is coded as codeset 0 to accommodate inter-vendor
connectivity.
Progress Indicator
The Progress Indicator information element describes an event that has
occurred during the life of a call and affects the handling of a call. It is
supported as a mandatory information element in the progress message and
optional in the alerting message. For examples of use of this element, refer
to "Termination to a non-ISDN trunk" and "Calls routed to treatment," in
Chapter 5, "Call control procedures."
The following conditions describe these events:
Redirecting Number
The Redirecting Number information element is the number from which call
redirection/diversion was invoked. Optionally, this information element may
be passed from user to user without network interpretation or interaction.
Redirection Number
The Redirection Number information element indicates the number to which
call redirection/diversion should be or has been invoked. Optionally, this
information element may be passed from user to user without network
interpretation or interaction.
297-2521-106 Standard 23.01 March 2001
A call is not end-to-end ISDN—The connection from source to
destination includes a per-trunk signaling trunk.
In-band information is now available—An event occurred that must be
told again to the originator of the call. When this information cannot be
sent out-of-band on the D-channel, it is sent as a treatment on a
B-channel.
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