CUBE early media feature to eliminate MTP

Unanswered Question
Feb 24th, 2009



-CUBE, 12.4(15)T3

CUCM is connected to Carrier SBC via CUBE and have a question regards the MTP requirement.

The only requirement for MTP is to provide 'intercept message' by carrier when dial out a long distance call without '1' in front of 10 digit by mistaken. when I enabled MTP in CUCM SIP trunk interface, IP Phone can get proper intercept message from carrier as exmaple 'please add 1 in front of your dial destination' but 'air dead' if I disable MTP.

As I know its 'early media' feature and I found CUBE support the following,


voice service voip

early-offer forced


Is the carrier 'intercept message' accomplished by 'early media' feature in CUBE? My goal is eliminate MTP requirement in CUCM side.

Thanks in advance,

I have this problem too.
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Nicholas Matthews Tue, 02/24/2009 - 13:46

If you're using 'early-offer forced' I would upgrade to a 20T or 22T version first, as I don't believe it's officially supported until 20T (though the command exists)

Is this call flow SIP-SIP or H323-SIP?

You may want to check the restrictions to make sure the call flow you're wanting to do, as a number of the situations where you would want to use early-offer forced aren't supported call flows. Here's a link for SIP-H323:

The intercept message is actually just a 183/180 with SDP, which isn't properly heard unless you have early media configured.



cjrchoi11 Wed, 02/25/2009 - 05:45

Hi Nick,

My case is sip-sip. can you give me some more detail about '183/180 with SDP' to communication to my carrier?



Nicholas Matthews Wed, 02/25/2009 - 06:02

Hi John,

What happens is this:

CUCM--SIP leg 1---CUBE---SIP leg 2--Provider

We are doing delayed offer on leg 1 since this is an outgoing call and CUCM doesn't have MTP required checked. This means that we do not have media information on where to send audio for CUCM.

After we send the invite on leg 2, without media, we will receive a 18x message that is designed for ringtone. If the message does not have any media in it, we will normally generate ringback ourselves. If it does contain media, we will open our audio stream. Frequently when it has audio it is the provider sending audio that is similar to "Your call cannot be completed as dialed ...".

In this case, if we do leg 1 with delayed offer and leg 2 with early offer, you should be able to get the media from the provider since we will send media (SDP) in our invite.



Nicholas Matthews Wed, 02/25/2009 - 06:40

Hi John,

This isn't really something to contact the carrier about.

I would go to 12.4(20)T2 and try the early-offer forced command and see what results you get.


dpaquet Thu, 05/20/2010 - 06:42

I work for ATT and we've deployed the CUBE for our/ATT's BVoiP/Flex SIP offering.  From what i've experieinced the early offer - delayed offer issue is different then the early media - delayed media issue.  When using Cisco SCCP phones you are forced to the delayed offer path and most carriers only support early offer.  So, the early offer forced command will fix the EO-DO issue, but it does not fix the EM/DM/PRACK/183 issue.  We worked with TAC and we were forced to "require MTP" for all calls using our SIP-CUBEs trunk.  Bad news for us, we're currently running CUCM 6.X where only G711 is supported in this scenerio.  In CUCM 7.X you can specifiy either G711 or G729.


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