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AMA-CUCM Troubleshooting: Best Practices for Reading Trace Files

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Beginner

a-law to u-law

Is a transconding functionality with in a gateway (CUBE) would be manadatory if we are getting calls from the service provider (on a SIP trunk) through a-law and gateway is communicating to CM through u-law dial peer.

Service Provider ---a-law----> CUBE-----u-law----> CCM

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VIP Mentor

a-law to u-law

Yes you do. You will need a xcoder to convert from alaw to ulaw

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"opportunity is a haughty goddess who waste no time with those who are unprepared"

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Beginner

a-law to u-law

What will happen if we configure a-law on dial peer pointing to CCM and configure a-law on CCM sip trunk configuration pointing to gateway & also check the option 'Media termination piont required'.

VIP Mentor

a-law to u-law

If your codecs are the same then you dont need a xcoder as long as you dont have CUE which only supports ulaw. You dont need MTP..Why do you want to use it?

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"opportunity is a haughty goddess who waste no time with those who are unprepared"

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Beginner

a-law to u-law

The SIP trunk configuration does not allow me to change it a-law until i dont check the box 'Media termination point required'. we are not using CUE. I can't change the codec to a-law in service parameters due to some other constraints.

VIP Mentor

a-law to u-law

You dont change the codec used on the sip trunk that way..YOu configure region relationships between the region the sip trunk is in and the region your gateway is in. If the dial-peer on your gateway is G711aaw then conjfigure the region between your sip trunk and your gateway to g711alaw..You dont need to touch the MTP part

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"opportunity is a haughty goddess who waste no time with those who are unprepared"

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Beginner

a-law to u-law

in the region setting it simply provides the option of G.711 and does not provide a selection option for ulaw & alaw and when i simply select the G.711 in region settings it appears as ulaw in the trunk config.

VIP Mentor

a-law to u-law

Thats is fine, CUCM supports both g711alaw and ulaw (even though you see only g711) Just configure your cube to use alaw

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"opportunity is a haughty goddess who waste no time with those who are unprepared"

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Cisco Employee

a-law to u-law

Hi Rehan,

The Region setting defines the upper limit of the codec which are allowed to use. Thus, if we configure G711 between the region of the phones and the SIP Trunk, the CUCM will advertise all possible codecs which have a more complexity ratio than G711 including all flavors of G711, i.e. G711alaw, ulaw, G729, G723. This is ofcourse considering that the IP Phone making the call also supports them.

Similarly, the gateway will advertise its own codecs, where as suggested you can hardcode G711alaw under the dial-peer configuration. This will make sure that the codec negotiated is indeed G711 alaw.

Regards,

Jagpreet

Beginner

a-law to u-law

But this call be going to IPCC express through CCM, will alaw work with IPCC express setup as well?

If we transcode the alaw to ulaw on gateway then PVDM3-32 can transcode how many silultaneous incoming alaw calls to ulaw.

Cisco Employee

a-law to u-law

Rehan,

     I believe IPCC can only do G711 ulaw. I dont have the access to a sever right now. But if you do then you can confirm the same under its Service Parameters. If it says just G711 then it can do both ulaw and alaw.

Also, if we are not using the PVDM3-32 module in a shared environment, then since this is a "low complexity" use, you could probably run 32 active calls. Although most IOS versions will not let you configure "low" as a codec complexity type. The options available are "medium" or "high" in the IOS help, medium gives you 21 simultanous calls and high gives you 16.  However, you can also configure "flex" complexity which will give you the same number as low. This might not show up in the IOS help when configuring.

Regards,

Jagpreet

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