SIP Trunk and Consultative Transfer, Early Attended Transfer and Blind Transfer issue

[ysanadiga01]

Hi there,

I'm working with a SIP service provider on a new SIP Trunk. When I don't use MTP, I have an issue with Consultative Transfer,  Early Attended Transfer and  Blind Transfer. But when I use MTP all three transfer types are working. 

Is there a way to let Consultative Transfer,  Early Attended Transfer and  Blind Transfer work without using MTP.  I'm using Cisco CUCM 9.1.

Any help will be highly appreciated.

Thanks & Regards,

Sana

[Tony Cilli Jr]

If you're doing SIP Early Offer, then an MTP is required. Using SIP Delayed Offer could possibly alleviate this.

Are you doing a ton of calls, or is your CUCM CPU spiking? Otherwise, there shouldn't really be an issue with using an MTP. Unless you're using DSP's to do it... Or if your carrier is offering a different version of G711 than you're using (alaw vs ulaw). 

Have you ran any debugs yet that you can provide of the SIP Messages?

Regards,

-Tony