Messages between CVP and CUCM that I do not expected

[CoDeC]

Hello,

This discussion is not for some issue, all works fine. I'd like try to understand the conversation that there is between CVP and CUCM.

Versions:

CUCM 10.5

CVP 11.0

UCCE 10.5

CUSP 8.5.9

IOS 15.4(3)M2

My scenario is:

In my opinion, all traffic between CVP and CUCM have to be through CUSP but in the CUCM's traces I see SIP messages (in/out) between CVP and CUCM directly.

It would be appreciated if you can explain me this behaviour.

Best Regards,

[Chintan Gajjar]

ok, so what you are seeing looks to be expected between CUCM and CVP.

there is option on CUSP and the option is called "SIP Record Route".

the option determines whether the CUSP will be involved in all the signalling between two devices or will just route the initial request and get out of the loop between the SIP devices.

By default the Record Route feature is turned off on SIP Proxy, and in this case the CUSP will just route the initial request between SIP devices and get out off loop.

In case of Record Route is On, the CUSP will add its own routing header when forwarding the SIP request and destination device has to contact back the CUSP for further SIP transactions and it this case all the SIP signalling will pass through CUSP.

Hope it Helps.

Regards

Chintan

[CoDeC]

Hi Chintan,

thank you.

make sense in my scenario because we have disabled the Record Route feature.

then, my next doubt (I know that I have to improve in the sip protocol knowledge), if in the CUCM there is only defined the SIP Trunk to/from CUSP (there is not SIP Trunk to/from CVP), why the conversation between CVP <> CUCM is allowed?

regards,

--

Alberto

[Chintan Gajjar]

To My Knowledge, it's allowed because initially the CUCM sees the call coming over the SIP Trunk connected to CUSP and based on VIA and Contact header it will send response directly to the far end device.

[Anand Krishnakumar]

To add to what Chintan said,

If you see the SIP traces - CVP / CUCM,

CUSP will go away from picture when " SIP ACK" response is sent.

ACK messages are sent directly between source and destination and CUSP will not be available at that stage as record route is disabled.

Thanks,

Anand

[CoDeC]

Hi Anan,

thanks for the contribution

regards,