Need to Send Early Offer to SIP Phone from CUCM

[courtschuett]

Using CUCM 10.5 and Cisco 8865/9971 phones with SIP loads.  I have calls going between them successfully and calls to PSTN working correctly.  Calls from the phone to the CUCM and out to PSTN correctly have SDP in the initial INVITE.  However, calls from the CUCM to the phone do not have Early Offer.  Enabling MTP Required on the Device does cause the CUCM to send Early Offer, but that is not a practical solution.

Phone -> CUCM - Early Offer

CUCM -> SBC - Early Offer

CUCM -> Phone - Delayed Offer

Any ideas?

[Shalid Kurunnan Chalil]

Hi, 

You can use Best Effort (No MTP Inserted) for early offer support for voice and video. This will send an early offer by call manager where ever it is possible. you can find below snapshot for better understanding. 

You can find this configuration element in SIP Profile.  

• Early Offer support for voice and video calls Best Effort (No MTP inserted) — also known as Best Effort Early Offer

Regards,

Shalid

Please rates helpful posts. 

[courtschuett]

That worked for the CUCM -> SBC INVITE.  I am trying to resolve the CUCM -> Phone INVITE.  Enabling Early Offer (Best Effort) in the SIP Profile did nothing for the INVITE from the CUCM to the Phone.

So this works:

Phone --EO--> CUCM --EO--> SBC --> PSTN

This does not:

PSTN --> SBC --EO--> CUCM --DO--> Phone

[pablo.ahmed]

Hi Courtschuett,

Did you finally figured out an answer for your question?
I have exactly the same question than you. I would be really grateful if you share the answer with me (if you have it)
Best regards,

[Roger Kallberg]

Out of curiosity may I ask what use case you have for having early offer sent from CM to the phone?

[Steffen Wentzel]

Hi, currently having the same challenge as the op: I need CUCM to use EO to a 3rd party SIP device.

The use case here is that we want to test the open source "Blink" SIP softphone, which seems to accept EO INVITEs only. It responds with "488 Not Acceptable" in case of DO INVITE.

Currently my only workaround is also to enable "MTP required", which of course does not scale. Any SIP Profile options as mentioned before only apply for SIP trunks (i.e. "Best Effort" etc.).

BR, Steffen

[Maren Mahoney]

The phone configuration page in CUCM also has SIP Profile. Have you tried applying a SIP Profile on the phone configuration page that includes the 'Best Effort (no MTP)' setting?

Maren