We are upgrading our phone network to Cisco AVVID. We need to interate our AVVID platform during the upgrade with a Nortel BCM. Our only option will be using H323 for interoperability.
I have supplied a message from a Nortel Eng. as to why the 2 will not work. Are there any Cisco H323 users that would like to add there 2 cents. He seems to point to the Call Manager as the problem.
1) Payload size
Problem: During H.245 capabilities exchange, BCM announces that it supports G.729 with a 30 ms payload size and Cisco announces G.729 with 60 ms payload. After that, BCM opens a logical channel with a 30 ms payload size (the biggest size that fits both) but Cisco opens a logical channel with a 20 ms payload size.
Although one can argue that this does not violate the standards (since 20 is smaller than 30), it does conflict with BCM's assumptions (and the Nortel H.323 Interoperability Specification). That is why BCM treats this situation as an error.
2) RTCP Address
Problem: From what I have seen in the Sniffer traces, there seems to be a bug in the Cisco Call Manager. The standard (section 6.2.8.2 of H323v2) specifies that the RTCP address+port in OLC for one channel must be the same as the RTCP address+port in the OLC-ACK for the other channel. However, what I observed in the Sniffer traces is:
CiscoCM to BCM
<---OLC mediaControlChannel=10.100.118.5:28001---
---OLC mediaControlChannel=10.100.118.4:4001---->
---OLC-ACK mediaChannel=10.100.118.21:27856,
mediaControlChannel=10.100.118.21:27857------>
Note that the trace shows that the Cisco Call Manager sends OLC before it has talked to the IP set. That probably explains why the parameter in the OLC is incorrect.
Preferred solution: Fix Cisco Call Manager so that it sends the same RTCP addresses for both logical channels.
