To obtain an estimate of the additional traffic the Messaging system will add to your network, you can calculate the bandwidth usage between the application servers and the storage server. The calculation must include the number of application servers in the Messaging system, the number of ports on each application server, and usage characteristics. The encoding method you use is also a key factor.
For a worst case estimate of network load added by a Messaging system using the G.711 encoding format, which has a bit rate of 64 kbps, the formula is:
number of servers X the number of ports on each server X 64
For a site with a Messaging system containing three application servers, each with 100 ports, the formula is:
3 X 100 X 64 = 19,200 kbps
If you use the GSM 6.10 encoding format, which has a bit rate of 13 kbps, the calculation for this site yields the following:
3 X 100 X 13 = 3,900 kbps
This calculation is based on the assumption that all ports are recording or playing voice data at the same time. Note that this formula estimates the total network traffic potentially added but does not indicate how many ports receive calls and how many ports make calls. To allow for the overhead used by the network protocols and options, add 10% to the result. Note that this worst case network load calculation does not include burst rates caused by bursty message deliveries or bursty message playback.