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Traffic engineering
198 Avaya Application Solutions IP Telephony Deployment Guide
 
A seven-site COI matrix analogous to the three-site matrix in 
on page 184 can be constructed for the network shown in 
. A corresponding seven-site, expanded COI matrix, similar to the one in 
on page 192, can also be constructed. 
However, when multiple systems are networked together, the additional step of engineering the 
tie trunk groups must be performed. To do this, the COI matrices are used to determine the 
traffic flow between each pair of Avaya systems.
In the network that is shown in 
, IP Trunk Group 1 carries calls between Sites 1 and 3, 
Sites 1 and 4, Sites 2 and 3, and Sites 2 and 4, in addition to a presumably small amount of 
overflow traffic that involves other sites. The traffic load that is associated with such calls is used 
to size that trunk group. Tie trunk groups are typically sized at either P01 (1% blocking) or P03 
(3% blocking). In a system such as the one in 
, the traffic engineer must account for 
overflow traffic. The traditional Wilkinson model is an effective tool for doing so. However, for 
systems that have larger numbers of systems in the network, there can be many possible paths 
between a given pair of systems. In such cases, determining the hierarchy of paths to consider 
for calls between two systems is not always straightforward. The analysis involved in sizing the 
tie trunk groups in topologies such as those can be quite complex.
Resource sizing
This section provides a description of the resources that have the potential to be bottlenecks, 
and a discussion about how to engineer them. This is the final stage of the design process.
Overview
The primary Communication Manager resources that have the potential to be bottlenecks are:
the TN799DP C-LAN (Control LAN) circuit packs 
the port network TDM bus pairs
the TN2602AP IP Media Resource 320 and TN2302AP IP Media Processor circuit packs
the TN2312BP IP server (IPSI) circuit packs
the server’s processing capacity
IP bandwidth.