CUCM, CUBE, SIP and MTP Requirements

[ehempton]

Hi all,

I wanted to get some perspective on the MTP requirements that may or may not be required with the lastest software versions.

The scenario is as follows:     ITSP<---SIP Trunk--->CUBE<---SIP Trunk--->CUCM

The CUCM is running version 9. The CUBE software is the lastest version.

In CUCM by default a SIP invite is without SDP and therefore delayed offer. In common with most providers the ITSP wants invite with DSP, early offer.

My understanding is that the CUBE can be configured on a per dial peer basis to set either early or delayed offer.

In this case when a call originates from CUCM it will send an invite DO to the CUBE who will then send an invite EO to the ITSP, assuming that the dial peer is appropriately configured.  In this way CUCM will not need an MTP but what about the CUBE?  Does it require an MTP or is this negated as the invites travel through the dial peers and are effectively terminated and regenerated here?

Also, for incoming calls from the ITSP to CUCM, my understanding here is that MTPs are not required, although the SRND for CUCM9.x doesn't expand on this statement. Is this correct?

Thanks,

[Ayodeji Okanlawon · Accepted solution]

Hi,

The best practice is to have CUBE send EO to ITSP with your desired codecs. For this CUBE does not need an MTP.

On the inbound leg, there is also no need for MTP as your provider will send you a list of codecs they support.

To understand more abour codec selection and offer please have a read on this document..

https://supportforums.cisco.com/docs/DOC-26098

To understand a little more of what you need MTP for in a sip deployment, look at the SIP trunk section of the SRND.

In a short summary,

MTP is needed in these scenarios

1. DTMF mismatch eg h323 to sip or mgcp to sip deployment using traditional DTMF method.

2. Media termination in a uccx deployment over sip trunks

3. Trans rating/re-packetization I.e converting from 20ms packetization to 30ms

4. Supplementary services in some scenarios

5. SDP offer in early offer on a sip trunk

6. Fast start on h323 gateways.

7. Stop re-invites during call hold over sip trunks from been sent to the ITSP.

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[ehempton]

That's very helpful, thanks very much.