SIP early offer with CUBE

[techToddler]

Hello Friends,

I appreciate if someone could help in understanding my questions below.

We have a setup as

IP Phone --> CUCM --> SIP TRUNK--> SME ---> SIP TRUNK --> CUBE

1. I know what is early offer but would like to know if it has be enabled throughout this path. Like on the CUCM and SME?

2. What is the difference is Best effort and Mandatory for MTP in SIP profile? For example if I say, I have enabled early offer from CUCM and not in SME. Perphaps Service provider sends me only G729 as preferred for them.

I wanted someone to explain me with an example and that would be highly appreciated.

Regards

Sanjay

[Chris Deren]

EO is enabled via SIP trunk profile that is assigned to the SIP trunk in CUCM. You should never force an MTP unless you know that is required for specific call flow, which it is not usually needed between Cisco only components such as the call flow you describe. The quick way to see if EO is being used is to look at the original SIP INVITE message and see if you have an SDP content. Some good examples and excellent descriptions can be found on our very own VIP Ayodeji's post:

https://supportforums.cisco.com/document/113271/understanding-sip-traces

[techToddler]

Thank you so much for your response.

I wanted to understand why an important is given to MTP?

As far as I understand its a thing which accepts two streams and mix or torn them as required. But what does it do here.

I am early offer from CUCM to SME. But SME to CUCM of another cluster its delayed offer. What will happen here?

Regards

Sanjay

[Chris Deren]

Read about it in SRND:

http://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/srnd/collab11/collab11/media.html#77886

Essentially MTP in context of EO vs. DO can be engaged to convert between the two. For example if you send an INVITE without EO, but the other side expects it MTP can merge the streams and convert between DO and EO.

[techToddler]

Thank you

Sanjay

[Adarsh Chauhan]

Hi,

Answer to your question number 1:

If EO has been enabled on CUCM and SME.

a) Check if MTP is checked

b) Check the SIP profile configuration on the SIP Trunk

Answer to your question number 2:

Mandatory (insert MTP if needed)

Unified CM does not need to insert an MTP to create an outbound Early Offer call over a SIP trunk if the inbound call to Unified CM is received by any of the following means:

• On a SIP trunk using Early Offer
• On an H.323 trunk using Fast Start
• On an MGCP trunk
• From a SIP-based IP phone registered to Unified CM
• From newer SCCP-based Cisco Unified IP Phone models registered to Unified CM

Best Effort Early Offer 

SIP trunks send outbound calls with an Early Offer in the following situations:

• An inbound call to Unified CM or SME is received over a SIP trunk using Early Offer.
• An inbound call to Unified CM or SME is received over an H.323 trunk using Fast Start.
• An inbound call to Unified CM or SME is received over an MGCP trunk.
• A call is initiated from a SIP-based IP phone registered to Unified CM.
• A call is initiated from a newer model SCCP-based Cisco Unified IP Phone registered to Unified CM.

Best Effort Early Offer trunks send outbound calls with a Delayed Offer in the following situations:

• An inbound call to Unified CM or SME is received over a Delayed Offer SIP trunk.
• An inbound call to Unified CM or SME is received over an H.323 Slow Start trunk.
• A call is initiated from an older model SCCP-based IP phone registered to Unified CM.

To understand EO with SIP trunk I would highly recommend to go through the following document.

Unified CM SIP Early Offer

Please rate and mark correct if helpful

Regards,

Adarsh Chauhan