[asterisk-users] Bandwidth requirements for 1, 000, 000 minutes a month

[Steve Edwards]

This may expose my ignorance, but here goes :)

I've been asked to figure out how much bandwidth would be needed to handle 
1,000,000 minutes a month.

Here's the environment:

) All calls are received via SIP.

) All calls use the ulaw codec.

) Calls average 10 minutes in duration.

) The "busiest" hour will account for 10% of the daily total.

This is how I'm figuring it...

Casual observation shows that SIP setup and teardown takes about 26 UDP 
packets. Assuming the packets are full (512 bytes) this adds up to about 
13 kilo-bytes for each call.

I've heard that ulaw (including overhead) is supposed to take about 80 
kilo-bits/sec.

Assuming each call takes 10 minutes, each call will take 13 kilo-bytes + 
(80 kilo-bits * 60 * 10) or 48.13 mega-bits. Assuming (to make the math 
easier) 10 bits = 1 byte, each call will take 4.813 mega-bytes.

So, 100,000 calls of 10 minutes (1 million minutes) would consume 481,300 
mega-bytes per month or 3,333 calls consuming 16,043 mega-bytes per day.

Assuming the busiest hour accounts for about 10% of the daily total, that 
hour would consist of 333 calls consuming 1,604 mega-bytes.

So, my "peak" would need 4.5 mega-bits per second of bandwidth.

Am I in the ballpark?

Would anybody venture an estimate of what the peak bandwidth would be if 
we changed to IAX? With trunking?

Thanks in advance,
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Steve Edwards      sedwards at sedwards.com      Voice: +1-760-468-3867 PST
Newline                                             Fax: +1-760-731-3000