call preservation over ICT (non-Gatekeeper controlled)

[Marcel Imrich]

Hello.

I want to clarify one call routing situation. As described in Cisco configuration guide it is possible to

have call (media stream) preserved in case of active Call Manager server failure. This is fine for standard H.323 gateways

but is it possible to achieve this (full redundancy) for Inter-cluster trunk between 2 different UCM clusters?

I know, there are some situations where the call stays active but it depends on which UCM route the call from ICT.

Thanks.

Marcel

[Manish Gogna]

Hi Marcel,

Call preservation works for ICT as well, you may check the following

http://www.cisco.com/c/en/us/td/docs/voice_ip_comm/cucm/admin/9_1_1/ccmsys/CUCM_BK_C5565591_00_cucm-system-guide-91/CUCM_BK_C5565591_00_cucm-system-guide-91_chapter_01011.html#CUCM_RF_C98194B0_00

There was however one bug related to call preservation across ICT which you can find below

https://tools.cisco.com/bugsearch/bug/CSCsd96316/?referring_site=bugquickviewredir

Apart from the above there are no limitations that i am aware of.

Manish

[Marcel Imrich]

I thought so, until we've run in a situation where in case of active Call Manager which handles the call thru ICT fails. This immediately drops the call on the remote site (cluster). I'll try to investigate the issue, as this should be the very same situation as calling between two endpoints in the same cluster.

Marcel

[Manish Gogna]

Hi Marcel,

The call will not drop, it may experience one way audio in some specific scenarios like the one described in the following bug

https://tools.cisco.com/bugsearch/bug/CSCul90883/?reffering_site=dumpcr

One-way audio call happens when CCM service is stopped in H.323 ICT call

CSCul90883

Description

Symptom:
Call Preservation does not work fine then one-way audio happens when SDL Link Out of Service is detected.

Conditions:
The issue happens with calls through Gatekeeper or non-Gatekeeper ICT.
Here is an example of an environment that it is seen:

Call Flow:
IP Phone A ---- CUCM#1(*) ---- CUCM#2 ---- Gatekeeper or non-Gatekeeper ICT ---- CUCM#3 ---- CUCM#4 ---- IP Phone B

Service parameter :
Allow Peer to Preserve H.323 Calls is TRUE

Steps:
1. IP Phone B places a call to IP Phone A and the call is established.
2. Stopping CCM Service on CUCM#1(*) for testing.
3. CUCM#2 detects SDL Link Out of Service and sends CloseLogicalChannel to CUCM#3.
4. One-way audio issue is seen on IP Phone B side.
IP Phone B cannot hear audio from IP Phone A. <<<<<< Strange behavior
IP Phone A can hear audio from IP Phone B.

Workaround:
Using SIP Trunk.

Further Problem Description:
- If the call is placed from IP Phone A to IP Phone B, the issue does not happen.
- If stopping CCM on CUCM#4, call from IP Phone A to IP Phone B faces the issue.
One-way audio issue is seen on IP Phone A side. IP Phone A can not hear audio from IP Phone B.