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New Member

Why h323 gateways drop calls in case of CCM failure

Hi all,

Just for information...

I'm wondering why an h323 gateway drops calls in case of CCM failure.

Someone on this forum said that the CCM acted as 'man in the middle' during a IP-Phone to external phone communication.

But I thought that once the UDP/RTP stream was established (after signaling to/from a gatekeeper), there was no communications any more between devices and gatekepeer (except for call ending)...

By the way, a call between a skinny phone and an H.323 netmeeting stays up in case of a CCM failure...

Did I miss something ?

Can somebody tell me the full interactions between these 3 devices during an external call: IP-Phone/CCM/H323 gateway.

Thanks in advance,

Manuel.

4 REPLIES
New Member

Re: Why h323 gateways drop calls in case of CCM failure

Hi Manuel! I'm not sure about your argument. The behaviour will be same in both the cases. The call will get dropped. The reason being the IP Phones will be reset by CCM when it goes down.

New Member

Re: Why h323 gateways drop calls in case of CCM failure

Thanks for your input,

But I think you're wrong: the IP-phone stays up while in communication, if the CCM is shut down.

It just displays something like "CCM down, limited features..." and it reset once I hang up.

It's the same behaviour for a skinny-to-skinny call than for a skinny-to-netmeeting call. The call stays up.

BUT for a skinny-to-H323gateway call, the call gets drop in case of CCM failure.

It must be some kind of keepalives between CCM and H323gateway ??? (which is not described in the H323 standard, is it?)

Any help ?

Thanks,

Manuel.

New Member

Re: Why h323 gateways drop calls in case of CCM failure

Hi,

The H.323 gateway establishes a TCP connection to the active Call Manager server for the entire period of the call. In the event of a active call manager server failure, the call will get disconnected because the TCP connection between H.323 gateway and the active call manager server is lost.

MGCP will provide call redundancy as the gateway establishes connections to

both call manager servers, in the event of a active call manager server failure, the gateway will use the alternative connection to the other Call Manager server, thus the call will not be dropped in this case.

Kim Yin.

New Member

Re: Why h323 gateways drop calls in case of CCM failure

Thanks Kim,

And what this TCP connection is for during an H.323 call?

What kind of infos are exchanged on this TCP channel ?

I mean, if a H323 netmeeting call works without this connection, why does a CCM needs it with an H.323 gateway... ?

For MGCP, I agree with the immediate alternative connection in case of a CCM failure, but moreover, if you have a single CCM and it fails, the call through this MGCP gateway stays up...

Cheers,

Manuel.

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