118 ITG engineering guidelinesTAT versus TRONortel recommends that both Trunk Route Optimization (TRO) and TAT beimplemented with IP Trunk 3.01 (and later) nodes.TRO functions in a different manner than TAT. TRO is invoked before the callhas been answered. TAT is invoked once the call has been answered. Toreduce the number of trunks being used due to call redirection by CFNA,Hunt, or Forward all Calls, configure TRO in the RDB. TRO must be enabledat all sites.If Telephone A at Site 1 calls Telephone B at Site 2, and Telephone Bforwards a call using CFNA to Telephone C at Site 3, then TRO must beenabled at Sites 1 and 2. If TRO is enabled at both sites, Site 2 will dropout, freeing up the trunk, and only trunks on Site 1 and 3 are used. Thisreduces the number of trunks in use, conserves bandwidth, and improvesvoice quality.The TRMB prompt in RDB does not have to be set to Yes for TAT or TRO towork. The function of the TRMB prompt is to allow or disallow tromboningcaused by NARS/BARS mis-configuration. For example, Site A has DSC of4000 pointing to Site B. Site B has DSC of 4000 pointing back to Site A. If acaller at Site A dials 4000, this can lead to the call orbiting between the twosites. This is commonly referred to as the "Ping-Pong" effect. Therefore,Nortel recommends setting TRMB to NO.WAN route bandwidth engineeringAfter the TLAN subnet traffic is calculated, determine the bandwidthrequirement for the WAN. In this environment, bandwidth calculation isbased on network topology and destination pairs.Before network engineering can begin, obtain the following network data:• A network topology and routing diagram.• A list of the sites where the IP Trunk 3.01 (and later) nodes are to beinstalled.• List the sites with IP Trunk 3.01 (and later) traffic, and the codec andframe duration (payload) to be used.• Obtain the offered traffic in CCS for each site pair; if available, separatevoice traffic from fax traffic (fax traffic sent and received).• In a network with multiple time zones, use the same real-time busy hourvarying clock hours) at each site that yields the highest overall networktraffic. Traffic to a route is the sum of voice traffic plus the larger of oneway fax traffic (either sent or received.Nortel Communication Server 1000IP Trunk FundamentalsNN43001-563 02.01 StandardRelease 5.5 21 December 2007Copyright © 2007, Nortel Networks.
