voice-class sip pass-thru content sdp and codec transparent relationship on the same dial peer

[anilkumar.cisco]

Hello Team,

Can anyone explain,

Call between two CUCM Cluster is via CUBE

below is the diagram.

CUCM- CUBE-CUCM

the requirement is CUBE terminate media traffic but pass through codec requested by the endpoint and we have to use codec transparent on VOIP Dial peer.

I am confused with the below dial peer..

dial-peer voice XXXX voip
 destination-pattern XXXXXXX$
 session protocol sipv2
 session target ipv4:X.X.X.X
 incoming called-number XXXXXXX$
 voice-class sip pass-thru content sdp
 dtmf-relay sip-kpml rtp-nte
 codec transparent
 no vad

and my confusion is whether I have to use voice-class sip pass-thru content sdp command or not

and what would be the relation between codec transparent and pass-thru command.

Kindly advise.

[Jonathan Schulenberg]

You only need codec transparent. The other command is used for media flow-around, which is not what you want.

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/voice/cube_sip/configuration/xe-3s/cube-sip-xe-3s-book/voi-conf-pass-thro.html

Jusf be careful - I have had to abandon the codec transparent command in favor of a traditional codec preference list on a few occasions due to limitations. For example, it doesn’t work with dial-peer recording or early-offer forced.

[anilkumar.cisco]

Hello Jonathan Schulenberg thanks for your reply..

but after my research I am not satisfied with your answer..

the document provided by you itself says that. pass through can also do in media-through mode and will terminate media.. then where is the question of media flow around??

we need to enable media flow around then only passthrough with media flow around will work otherwise it will work as flow through mode..

Can you relook into my question and re-answer it pls.

Best Regards

Anil

[rchaussee]

Hi,

Session Description Protocol (SDP) pass-through is addressed in two modes:

• Flow-through—Cisco UBE plays no role in the media negotiation. It terminates and reoriginates the Real-time Transport Protocol (RTP) packets irrespective of the content type negotiated by both endpoints. Flow-through supports address hiding and Network Address Translation (NAT) traversal.

It seems, you can use both conmmand on the dial-peer : codec transparent + voice-class sip pass-thru content sdp

[pkinane]

"You only need codec transparent. The other command is used for media flow-around, which is not what you want."

This is not accurate. You can still do flow through.

[pkinane]

.

[rchaussee]

Do you know excatly the difference between them ??

Because for me the goal of this 2 commands is the same !

[pkinane]

.

[rchaussee]

But I got an issue with ptime with only codec transparent !

I received a ptimes:20 from CUCM (delayed offer) and then CUBE sent no ptime to other CUCM..

Finish the call by 200 OK with ptime: 30 !! and issue with unity connection...

[pkinane]

.

[rchaussee]

Ok

So maybe I need only codec transparent...

[agalbiatti]

Not 100% sure about that, but here is my understanding:

Codec transparent will just pass the sdp portion related to codec content untouched btw the call legs, but other fields on the sdp (like payload types for Video) cube still changes.

When enabling SDP pass thru, all parameters from the incoming SDP will be copied to the outbound call leg.

You can check this by enabling debug ccsip messages and compare minor changes at the sdp portion.

Also, seems that sdp pass-thru has preferece over codec transparent.