[Asterisk-Users] OT: Calculating Bandwith

[Rich Adamson]

> I am trying to calculate bandwidth needs.  Is 1 T1 Line able to provide
> 488.5 Gigabytes of traffic for 1 month based on a 30 day week?   I did my
> calculation as follows:
> 
> 1.544 mps * number of seconds in a minute(60) * number of minutes in a hour
> (60) * number of hours in a day(24) * number of days in a month(30) =
> 4002048 megabits / 1024 = (3908.25 gigabits)  / 8 = (488.53125 gigabytes) of
> bandwidth for a T1 Line.
> 
> Please correct me if I am wrong.

If you're doing the above calculations for the purposes of engineering
bandwidth requirements for * trunking (whether sip or iax), then you might
want to consider doing this using a shorter timeframe (maybe an hour as one
example).

The telephony engineering types that do this for a living often times use 
"peak busy hour" traffic to engineer bandwidth, and express their calculations 
in terms of what the probability is of a user incurring blockage (no bandwidth
available) during that period. That would imply calculating the bandwidth
available per hour, dividing the bandwidth consumed per codec, etc, to 
reach a number that says something like "x number of simultanous calls can
be supported". The x+1 call will fail 99% of the time (or some such approach).

Of coarse, one has to consider each type facility (half duplex ethernet:
20% - 30% max before quality drops; full duplex ethernet: 90% roughly;
full duplex T1: ~95%; number of isdn trunks, etc, etc.)