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The sequence of the example call in Figure 5-3 is described as follows.
Information from the example is shown in italics.
Table TRKGRP
The call comes into the switch over D2MPRI. D2MPRI is a PRA250 trunk
mapped against the ISDN 900 logical terminal identifier (LTID). The LTID
(ISDN 900) indexes into table LTCALLS.
Table LTCALLS
Table LTCALLS provides initial translations for calls that can be routed over
the trunk group's LTID. Table LTCALLS includes:
the trunk group's LTID—defined in table LTDEF
the call type
— conveyed between switches by the Q.931 SETUP message
— determines the translations that will be used to route an incoming call
the initial translations route for the call
In the example, after table LTCALLS is indexed by LTID and CALLTYPE,
it supplies the necessary information to begin translation of the called party
number. The call type is PRISM. As shown in Figure 5-3, the LTCALLS
tuple associated with ISDN 900 and call type PRISM is the interexchange
carrier translation information (XLAIEC). The XLAIEC refinement
provides a call attributes index (CALLATTR); this index references into
table CALLATTR. In the example, the CALLATTR index is 600.
Table CALLATTR
Table CALLATTR contains various translations information used in
translating and screening DMS-250 switch calls.
In this example, table CALLATTR contains PRAX in the field
PRETRANSLATOR NAME and 8140000 in the field AUTHCODE. This
authcode is used in the same manner as authcodes filed against non-PRI
trunk groups. (For more information, see "Filed hotline numbers" in Chapter
7, "Feature interaction.") The authcode acts as an index into table
AUTHCODM.
Table AUTHCODM
Table AUTHCODM provides additional translations information, mainly the
serving translation scheme used later (in the example: 904).
The AUTHCODE field provides a means to bill calls originating on the PRI
and is captured in the call detail record accordingly. Also, the AUTHCODE
provides a way to indicate optional account code digits are required for calls
originating on that call attribute.
Digital Switching Systems DMS-250 ISDN Reference Manual MWC14 (CSP14)
Call control procedures 5-7
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