CUCM and SIP IP Phone Call Flow Early and Delayed Offer ( IP Phone to IP Phone not Trunk or CUBE )

[Carl Ratcliffe]

Hi Support Community

This query on delayed and early offer early offer is not relating to CUBE or any sort of SIP Trunk or ITSP it is purely related to CUCM and IP phone to IP phone call flow.

It is not a setting I have ever changed as IP phone to IP phone call setup just works however I have been looking at a lot of traces and something that I have always been unsure on is that when a SIP phone ( 8841 ) calls another SIP phone ( 8841 ) you see an early offer in the invite from the calling SIP phone to CUCM then CUCM sends the invite the called phone with no SDP using delayed offer for the call setup.

1 - Is this a normal setup

2 - What setting determines this, in the SIP profile I can only see early offered related to trunk settings.

Thanks, Carl Ratcliffe

[Mohammed al Baqari]

It is in the SIP profile itself. Even though its in SIP Profile under trunk
section, it will still apply to the phone. Give a try and let us know.

[Carl Ratcliffe]

Hi Mohammed 

Thanks for your response. 

The SIP profile for the phones is the default sip profile which has delayed offer but it still sends early offer in the invite of the calling phone then cucm sends the invite to the called phone as delayed offer.

I will amend settings on the sip profile and see if it makes a difference. Is this documented anywhere as everything referencing early and delayed offer is relating to trunks and cube, even in the help it states trunk related settings.

Thanks, Carl Ratcliffe 

[Mohammed al Baqari]

Hi Carl,

I don't recall seeing this referenced because it doesn't make a difference
for the phones as the phones interface with CUCM. Its an important thing in
trunks because usually trunks interface with 3rd party

[Carl Ratcliffe]

Hi Mohammed,

Tested with different SIP Profiles but doesnt matter if you assign deleyed offer or early offer to the phones the call flow is always Calling Phone Early Offer to CUCM then CUCM Delayed Offer to Phone.

This i suppose always gives the called device the choice of codec which is detailed in various forums relating to codec selection.

As you say its probably not referenced as it just works however when looking at traces it would be good for Cisco to confirm the SIP call flow between phones as thats when it can cause confusion.

Thanks, Carl Ratcliffe