[cisco-voip] CallManager ICT and IPCC Express transfer issues

[Tim Smith]

Hi Guys,
Apologies for the length of this, difficult to give a simple overview, as
there are lots of components and factors at play.
I havent posted the traces, debugs etc, as there is too many :) - trying to
narrow down the exact theory first!
I suspect a bug.. I am trying to narrow down where exactly still.
I have found some pretty close bugs - but I am not sure they should apply -
bug desc is a bit light on.

*Quick and dirty overview*
**
Site A - CUCM 6.1(2) (call this local)
Site B - CCM 4.1(3)sr3a (call this the remote)
Site B - IPCC Express also (G711) 4.0(4)SR1
Site B - Voice Gateway - H323 IOS gateway (ISR router)
Site B - Xcoder + Conf Bridge - SCCP on IOS GW (ISR) - no HW MTP
Site B - Software MTP on CCM

ICT between Site A and Site B
ICT is configured properly in terms of CCM group, CCM IP's, MRGL's.
MTP required is not ticked at either end.

*Problem*
**
Call flow looks like this:
 Local IP phone > CUCM 6.1(2) > ICT (G729) > CCM 4.1(3) > IPCC Express >
redirected to mobile phone via 3800 IOS H323 Gateway (12.4(9)T1)
**
Translation pattern in Site A - translates called party to CTI RP number in
Site B (Across the ICT)
CTI RP goes to IPCC Express application - for simplicity the test app uses a
re-direct to an external number (my mobile)
Have tested with an agent, and it works fine. It is to the external number
that is a problem.
Call is routed to H323 gateway
Call rings on my mobile number. Either I answer within about 2 rings and
then I get fast busy at both ends
Or I dont answer and again within about 2 rings it stops ringing my mobile
and I get fast busy at the calling phone
Q931 shows a "Temp fail" or sometimes possibly a "Resource Unvailable" I saw
Temp fail on most of my attempts.

On a failed call I see an SCCP setup request on the xcoder gateway - it
fails (does not setup either leg of the xcode session)
In the setup I see the local IP address, but no remote IP address (0.0.0.0)
Also in the debugs I see an RTP and RTCP error (no packet received)

*Wierd things*

Not all calls fail - I have received some succesful calls (using the same
flow as above) - not many though.
I usually have a couple of succesful calls after an ICT reset (on the remote
Site B)
Normal phone to phone calls are perfectly fine.. never have a problem.
Normal calls to IPCC express that invoke transcoder, and end up at an agent
in Site B are fine.. never had a problem.

*Couple of things I wanted to confirm really:*

   1. Normal CCM to CCM via ICT does not require an MTP resource? (never
   used on in the past)
   2. With the IPCC express app - docco states MTP is required if the CTI RP
   has first party control of the call. Since the script answers on the CTI
   port first. Is this true? should it always require MTP? (I have to dig up
   this reference again)
   3. I never trust RTMT completely. But looking at it, it does not seem to
   be using a software MTP for any of the calls across the trunk, even though
   MTP required is ticked.
   4. I also checked the CCM traces - i see the call, I dont see it ask for
   MTP, I do see it ask for xcoder though.
   5. Where should the Media Resources be allocated from? (From the IPCC
   Express MRGL? or the ICT MRGL?)
   6. Anyone seen anything like this?

*My next steps..*
**

   1. Probably a TAC case for one! :)
   2. The PSTN gateway has been rebooted.. want to try and see what happens
   without MTP required now.. just for giggles.
   3. Also wanted to try a hardware MTP - From design perspective - if an
   MTP is required - we should use HW so it can XCODE as well, and not invoke 2
   x media resources!

Cheers,

Tim
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