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New Member

IOS MTP

Hi,

i have set up MTP resources on IOS router to be used with Call Manager for alaw to ulaw conversion.

I configured three MTPs on the gateway, one for alaw, one for ulaw and one for clear and added all three of them to media resource list on Call Manager:

dspfarm profile 1

codec g711alaw

maximum sessions software 100

...

dspfarm profile 2

codec g711ulaw

maximum sessions software 100

...

dspfarm profile 3

codec pass-through

maximum sessions software 100

...

The SIP trunk between Call Manager and the gateway has MTP required checked and g711alaw codec as preffered codec, since most calls work with alaw towards the provider.

However, i want some calls to be ulaw, so i have set ulaw on specific dial-peers toward Call Manager.

The problem is that the MTP doesnt convert between alaw and ulaw as it should, so the only way i can make this work is if i use transcoding directly on the gateway.

Could the problem be with 3 different MTPs or with g711alaw preffered setting on the trunk?

Debug ccsip messages gives me "SIP 501 not implemented error" , q.850 65 cause code. If i use transcoding on gateway itself, it works, otherwise nothing is sent to Call Manager.

This is what i get, when i use transcoding (this is on call, but has 2 xcode and 2 mtp sessions):

19 19 xcode sendrecv g711u 18704 2000 10.110.1.2

19 20 xcode sendrecv g711a 18028 2000 10.110.1.2

16969882 16875147 mtp sendrecv g711u 17612 31540 10.110.1.6

16969882 16875146 mtp sendrecv g711u 19136 19424 10.110.1.2

(10.110.1.2 is the gateway, 10.110.1.6 is endpoint)

Best regards,

Marko

4 REPLIES
Bronze

Re: IOS MTP

If you are going from one codec to another, you are correct in thinking you'd need a transcoder instead of a MTP.

New Member

Re: IOS MTP

But shouldnt MTP take care of alaw to ulaw conversion also? As i recall this souldnt need a transcoder...

Cisco Employee

Re: IOS MTP

Hi Marko, you need a HW transcoder / MTP to go from alaw to ulaw.

SW MTP only supports: same codec and the same packetization time.

http://www.cisco.com/en/US/docs/ios/12_3/vvf_c/interop/intcnf2.html#wp1029614

Regards Kees

New Member

Re: IOS MTP

Cheers Kees, this is exactly it.

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