[Asterisk-Users] Medium volume 100% SIP/IAX PBX.

[Dinesh Nair]

On 18/09/2004 05:50 Chris Shaw said the following:
> or audio quality. If it's cost savings, you could push 25 calls through a T1
> using GSM encoding, but it would not sound quite the same as a regular line.
> If you use G.711 (mu/A-Law) then you would get toll quality audio but only
> be able to push about 17 calls through at once...

based on my albeit rough benchmarks, a T1 (1.5Mbps) should be able to 
handle about 46 calls with GSM and about 20 calls with ulaw. i just did a 
quick test with a single call as follows:

                 SIP/ulaw                    IAX/gsm
WellGate 3502A <--------> rl0 Asterisk rl1 <-------> IAXTel <--- IVR

# netstat -w 10 -I rl1 -d # sample at 10-second intervals
             input          (rl1)           output
    packets  errs      bytes    packets  errs      bytes colls drops
        509     0      40151        262     0      28768     0     0
        504     0      39759        254     0      28274     0     0
        506     0      39860        256     0      28324     0     0
        502     0      39571        254     0      28224     0     0

(this gives about 32kbps per direction for GSM, IP overhead inclusive)

# netstat -w 10 -I rl0 -d # sample at 10-second intervals
             input          (rl0)           output
    packets  errs      bytes    packets  errs      bytes colls drops
        250     0      93500        508     0     108712     0     0
        250     0      93500        501     0     107214     0     0
        250     0      93500        497     0     106358     0     0

(this gives about 87kbps per direction for ulaw, IP overhead inclusive)

i wasn't doing much talking, so the input figures from rl1 and the output 
figures from rl0 should be used. they match john todd's observation on the 
asterisk wiki.

without IAX trunking and making worse case assumptions on IP overhead, the 
above figures would be good. IAX trunking would save somewhat on IP 
overhead as per http://www.voip-info.org/wiki-Asterisk+bandwidth+iax2

-- 
Regards,                           /\_/\   "All dogs go to heaven."
dinesh at alphaque.com                (0 0)    http://www.alphaque.com/
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