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IOS transcoder sessions slow to start

I have two sites connected with gateway controlled interculster trunks. I configured the trunks so that calls between them would be g729. For some reason the phones get sent to my IOS transcoder (NM-HDV-FARM) instead of just using their own DSP's. I have plenty of transcoders so that's OK. However, the process is so slow that the calling party never hears the called party say "Hello". The call gets setup well ahead of the RTP stream. Their is some skinny protocol activity during the delay but I don't have voice sniffer to decode it. My gateway is running 12.2(15)T1 and my CallManagers are at 3.3(2)spC. None of the equipment is over 5% utilized.

Has anyone else come across this?

4 REPLIES
New Member

Re: IOS transcoder sessions slow to start

Hi William,

I would be loath to blame the transcoder resources themselves since their allocation and invocation is a function of the Media Resource Manager in Callmanager.

Have you tried establishing the two-way audio path as soon as the RTP channel is opened by using the voice rtp send-recv global config commands on the gateways?

Regards,

Michael.

New Member

Re: IOS transcoder sessions slow to start

I am using the voice rtp send-recv command. Once the RTP stream starts everything seems OK. It does seem to be the interaction between CM and the DSP resource that is taking so much time. At first I suspected some network problem like slow ARP responses or weird routing, but my sniff shows that part is working fine.

New Member

Re: IOS transcoder sessions slow to start

Do you have the option of reconfiguring for testing purposes so that the call between the two sites uses G711 in order to obviate the need for transcoding resources? If so, what is the result of the test call?

Regards,

Michael.

New Member

Re: IOS transcoder sessions slow to start

I finally got this resolved. As everyone suspected the problem was not the transcoding. Instead it had something to do with Media Termination Points. I had the 'requires MTP' box checked on the trunk configuration. As soon as I unchecked MTP the delay went away. As a test I checked 'requires MTP' on one of my H323 gateway configurations and received the same results. Any theories on that?

Thanks for the input.

Bill C.

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