Installation guide

30 Planning and Installation Guide ShoreTel 14.2
Planning and System Design Trunk Requirements
2
Trunk Requirements
Trunks provide connectivity between users on the ShoreTel system and the public switched telephone
network (PSTN). In this next task in the system design process, you determine the number of trunks
required.
The number of trunks required on your system varies, depending on the number of users and your
specific application needs. It is important to size your trunking correctly because not having enough
trunks can lead to blocked calls when all trunks are busy, and too many trunks can lead to wasted
money on monthly access charges.
See Telephone Planning and Ordering on page 163, for more information about trunk features,
ordering, and installation.
You have several options for determining the number of trunks your site requires:
 Review the number of trunks on your current system. In general, this is one of the best methods to
gauge the number of trunks you need.
 You can also request a traffic analysis from your service provider, interconnect, or telecom
manager to understand your current trunk utilization. This method will help you understand your
current usage and allow you to maintain the current service level.
 Visit a web site, such as www.erlang.com, to use a traffic calculator for determining your trunk
requirements.
 Consider the following:

Larger locations can typically use lower-density trunking (15%).

Smaller locations need higher-density trunking (50%).

Some applications, such as call centers, can demand higher-density trunking (50%).
When planning trunks, consider the call volume for your workgroups or ACD groups. Since there is
generally a queuing solution in place for ACD calls, the number of trunks required should be based on
the full utilization of the expected number of agents and sufficient trunks for the expected number of
waiting callers.
Table 7: Trunk Density
Trunk Density Trunks/Users%
Low 15%
Average 30%
High 50%