Sizing

How to correctly size an IP/PSTN gateway or SIP trunk for Lync Server 2013 voice services is a common question and, unfortunately, is going to vary greatly depending on the users in each location. Sizing for an IP/PSTN gateway depends on the user’s dialing habits as well as whether any simultaneous ringing is configured.

Microsoft offers some planning numbers that can be used to perform a rough analysis. If at all possible, retrieve reporting data from the existing PBX to determine the expected usage requirements for each site. Table 32.1 offers a suggestion on how many PSTN ports to allocate to a site depending on the usage level. For example, in a branch office with 25 users with light usage, only two PSTN ports are suggested, but it is important for each business to determine whether these suggested numbers make sense for their own purpose.

Table 32.1. Voice Port Planning Figures