fast-start vs. slow-start in H323 VOIP gateway

[e.albajes]

Hello,

what's the difference between call-start fast and call start-start slow in H323 gateway? I'm looking for the difference in terms of bandwidth consumption and where it's best practically to be implemented?

Thanks,

Eyad

ealbajes@allianttech.com

[icabrera]

Hi, the difference between slow and fast start it's the way it's going to be started the communication. Fast start it's an improvement and it permits the setup to be fast, it needs h.323 v2 or greater. There's no difference in terms of bandwith consumption, here the important term is time not bandwidth because we are talking about signaling.

It's better to use fast start, as the name says it's faster to start a communication.

Regards

Hope this helps, if so pls rate the pots.

[e.albajes]

Thank you very much for the info.

best regards,

Eyad

[jbollen]

Hi,

The difference is the time needed to establish a conversation over H.323. In 'call start fast' a fastStart element is added to the H.225 setup indicating which codec, IP address and port to use for RTP. In 'slow start' there are implementations that wait until after the CONNECT to negotiate IP addresses, ports and codecs. In 'slow start' mode a lot more H.245 messages are exchanged over a (possible) separate TCP connection. In 'fast start' mode, the transmitted H.225 SETUP message is a lot larger (the more suggested codecs, the larger). Nowadays most H.323 networks use fast start unless there is an interoperability or incompatibility issue between products.

Sincerely yours,

Jan