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SIP trunk

hi guys

i have a gateway setup for testing as cme with sip trunk for pstn calls all good

i want to test it with CCM

if define it as normal h323 gateway will work normally or do i need to change any option


and if do it as bellow what is the binefit over the previous one !!!

CCM --sip--gateway--sip--ISP

thank you


Re: SIP trunk

Hi Marwan,

If you're running a newer version of CUCM (6+) then SIP-SIP is preferred. There are many things that are handled differently when CUBE has to translate H323 into SIP.

One of the factors is whether or not you will need an MTP. For the SIP-H323 connection you'll need an MTP for every connection to do supplementary services. For SIP-SIP you will not. There is a feature available for SIP-SIP called DO-EO or 'forced early offer' that allows CUBE to send an SDP before receiving one.

You'll find greater 'transparency' and les issues with a SIP-SIP CUBE than you will for H323-SIP. If you have a CUCM 5x or older, the SIP stack isn't as good however, and you may want to stick to using H323-SIP with an MTP.



New Member

Re: SIP trunk


My scenario is next:

CCM4.1 ---H323---Gateway---SIP/ISP.

What is actually the problem with the MTP? Can I use the gateway as MTP?



Re: SIP trunk

Hi Enrique,

The problem with the MTP is that it requires additional resources. If you have low volume this may not be an issue for you.

You can use the CCM or the gateway as an MTP. On the gateway you can use DSP resources or you can use software resources for this.


Re: SIP trunk

Nicholas is correct in his statements. CM 4.1 does a poor job in talking h323 to SIP. In most cases you will need an MTP to establish the calls. If you are low on MTP resources or none exist, the call may not complete or supplementary services will not work.