Factors that effectthe real-time capacity 117
TATcall Scenario
The following call scenario helps to understand TAT.
1. Site1 and Site 2 both have an IP Trunk 3.01 (or later) node installed. IP
Trunk3.01 (and later) is used for trunking between the two sites.
2. Telephone A at Site 1 calls TelephoneB at Site 2. TelephoneB answers
the call and decides to transfer the call to Phone C which is located at
Site A.
3. Telephone C answersthe call transferred from Telephone B at Site 2.
4. Afterthe call has been answered by Telephone C, Site B sends a TAT
Invokemessage to Site A. Site B only sends a TATInvoke message if the
TrombonedTrunks belong to the same D-Channel and Customer. If a
customer has multiple DCHIP cards in their node, The first leg of the call
could be associated with one D-Channel and the second leg of the call
associated with another D-Channel. In this case, TATwill not be invoked.
Toprevent problems, the following recommendations are made:
•The use of multiple DCHIPs in a node or the use of multiple IP Trunk
3.01 (and later) nodes in a system must be implemented with caution. It
can lead to poor voice quality in certain call scenarios.
•TrombonedTrunks must belong to the same customer.
•TAT must be configured in the RCAP prompt for D-Channel
Configuration. IP Trunk 3.01 (and later) Nodes atboth sites must have
TAT in the RCAP of their respective D-channels.
Therefore,TATcan fail if the originating sidehas multiple DCHIPsconfigured
or multiple nodes configured in a system. TATfailure can also occur if the
recipient of the TATInvoke message has multiple DCHIPs or IP Trunk3.01
(and later) nodes.
If Site A in the previously described scenario had multiple DCHIPs or
multiple IP Trunk3.01 (and later) nodes, TAT would fail. The reason is as
follows: if the call between TelephoneA and Telephone B was set up using
one D-Channel and the call between TelephoneB and Telephone C was set
up using another D-Channel, then the D-Channel for the first leg of the call
is not able to validate the Call Reference Value*for the second leg of the
call. This prevents TATfrom being used.
*The Facility message invoking TAT is sent using the Call Reference
Valueof the first call, which was from TelephoneA to Telephone B. The
TAT Invokeincludes the Call Reference Valueof the second call, which
was TelephoneB transferring the call to Telephone C.
Nortel Communication Server 1000
IP TrunkFundamentals
NN43001-563 02.01 Standard
Release 5.5 21December 2007
Copyright© 2007, Nor tel Networks
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