H323 Keep-alives

[Anthony Thomson]

I've a client with H323 calls dropping at the 1 hour mark; classic symptom of H323 or H225 timeout issues.

Problem is that the client has a network team (large client with many teams spread out geographically) refuses to adjust the timeout values on the firewall.

Is there a way to setup keep-alives on the endpoints or the VCS?  Endpoints are mostly MXP still, slowly being changed out for C-series.

Thanks.

[Paulo Souza · Accepted solution]

Hi Anthony,

Cisco/Tandberg endpoints use H245 messages to keep alive the call, they send H245 keep alive messages every 30 seconds. However, in some cases, the firewall does not consider the H.245 keep alive messages and then it disconnects the call if no H225 keep alive messages are received during a certain period of time (in your case, 1 hour).

The problem is, most of Cisco/Tandberg endpoints are unable to send H225 keep alive messages, only H245 messages (they use roundTripDelayRequest and roundTripDelayResponse messages). For TC endpoints, from TC6 and later, Cisco has provided a H225 keep alive feature, but the default timeout is 2 hours and that cannot be changed, so the endpoints keep alive the session every 2 hours.

For MXP endpoints, as far as I know, there is no H225 keep alive support, only H245.

Therefore, you will really need to fix the configuration in your firewall, once you cannot make any configruation change in the endpoints to solve the problem.

Take a look at this defect related to H225 keep alive issue for TC endpoints, note that Cisco suggests the customers to make adjustments either in the typology where the H323 (H225/H245) sessions are sent through or on the firewall device to accommodate the video traffic properly.

https://tools.cisco.com/bugsearch/bug/CSCub20591

Another people here in the community had the same problem, see:

https://supportforums.cisco.com/message/4039690?referring_site=bss&channel=bdp#4039690

https://supportforums.cisco.com/message/3952227?referring_site=bss&channel=bdp#3952227

I hope this help.

Paulo Souza

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[Anthony Thomson]

Thanks for confirming my suspicions, Paulo, and the link to the bug search article.

[Martin Koch]

It does not sound wrong what Paulo said, but I would assume that the root cause is that the

firewall is H323(/SIP) aware. Please disable these features, if they do not do it you might face

some other strange issues at some point as well (like randomly failing presentations, ...)

If its not right in the network it will not be right on the video system ;-)

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