118 ITG engineering guidelines
TATversus TRO
Nortel recommends that both Trunk Route Optimization (TRO) and TAT be
implemented with IP Trunk3.01 (and later) nodes.
TRO functions in a differentmanner than TAT.TRO is invoked before the call
has been answered. TATis invoked once the call has been answered. To
reduce the number of trunks being used due to call redirection by CFNA,
Hunt, or Forwardall Calls, configure TRO in the RDB. TRO must be enabled
at all sites.
If TelephoneA at Site 1 calls Telephone B at Site 2, and Telephone B
forwards a call using CFNA to TelephoneC at Site 3, then TRO must be
enabled at Sites 1 and 2. If TRO is enabled at both sites, Site 2 will drop
out, freeing up the trunk, and only trunks on Site 1 and 3 are used. This
reduces the number of trunks in use, conserves bandwidth, and improves
voice quality.
The TRMB prompt in RDB does not have to be set to Yesfor TATor TRO to
work. The function of the TRMB prompt is to allow or disallow tromboning
caused by NARS/BARS mis-configuration. For example, Site A has DSC of
4000 pointing to Site B. Site B has DSC of 4000 pointing back to Site A. If a
caller at Site A dials 4000, this can lead to the call orbiting between the two
sites. This is commonly referred to as the "Ping-Pong" effect. Therefore,
Nortel recommends setting TRMB to NO.
WAN route bandwidth engineering
After the TLAN subnet traffic is calculated, determine the bandwidth
requirement for the WAN. In this environment, bandwidth calculation is
based on network topology and destination pairs.
Before network engineering can begin, obtain thefollowing network data:
•A network topology and routing diagram.
•A list of the sites where the IP Trunk 3.01 (and later) nodes are to be
installed.
•List the sites with IP Trunk 3.01 (and later) traffic, and the codec and
frame duration (payload) to be used.
•Obtain the offered traffic in CCS for each site pair; if available, separate
voice traffic from faxtraffic (fax traffic sent and received).
•In a network with multiple time zones, use the same real-time busy hour
varying clock hours) at each site that yields the highest overallnetwork
traffic. Traffic to a route is the sum of voice traffic plus the larger of one
way fax traffic(either sent or received.
Nortel Communication Server 1000
IP TrunkFundamentals
NN43001-563 02.01 Standard
Release 5.5 21 December 2007
Copyright© 2007, Nor tel Networks
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