How many voice channels with cRTP and VAD

asapun · ‎03-20-2002

Does anyone know how many simultanious voice calls can 3600 router handle, running G.729b with cRTP and VAD enabled? I know that enabling cRTP on numerous voice calls is a processor intensive feature, but I cannot seem to find the limitation on the 3660.

By introducing CEF in newer IOS the number of calls has increased, but again I don't have those numbers.

Anyone?!

I would trully appreciate some input.

Thanks

msolak · ‎03-21-2002

Hi,

I hope it helps:

regards

Mehmet

Command:

ip rtp compression-connections

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To specify the total number of Real-Time Transport Protocol (RTP) header compression connections that can exist on an interface, use the ip rtp compression-connections interface configuration command. To restore the default value, use the no form of this command.

ip rtp compression-connections number

no ip rtp compression-connections

Syntax Description

number

Number of RTP header compression connections the cache supports, in the range from 3 to 1000. The default is 32 connections (16 calls).

asapun · ‎03-24-2002

Thanks Mehmet for your reply.

What I need to know is the capacity of the router itself to support numerous cRTP calls. Remember cRTP is processor intensive, and it may crash the router if too many calls are initiated.

msolak · ‎03-24-2002

Hi,

you can limit the numerous crtp calls with the command:ip rtp compression-connections.

The default is 32 connections (16 calls).

If you have an cpu intensity lower than 70% you can use cRTP without any problems.

Regards

Mehmet

asapun · ‎03-26-2002

In that case I guess my best bet would be to use a AS5400HPX w/ a 390-MHz RISC microprocessor.

Thanks for your help Mehmet, God bless.

asapun · ‎03-28-2002

Mehmet,

are you saying that you need 2 cRTP connections for one call?

Does that mean that 2 DSP processors are going to be used for one call?

Thanks

msolak · ‎03-28-2002

Hi,

no..you have still one DSP for one call.

I think Cisco means with 2 connectios (Calling and Called Party) 1 call.

Regards

mehmet

asapun · ‎03-28-2002

Thanks Mehmet,

why do you think than when using G.729b codec, a 120 DSP pool can only process 60 calls?

It looks like from what I'm undersanding, that when high complexity codecs are used such as G.729b, the voice cards' call capacity drops by half.

Is this your experience as well?

Thanks for your help, Mehmet.

keithj · ‎04-24-2002

You shouldnt have that problem using G.729b. G.729 does require an extra dsp (more processor intensive) as far as i know, the only diference between 729a & 729b is vad.

kj