Can anybody explain what exactly "h245 tunneling" is????/
A brief explanation is included here. http://resource.intel.com/telecom/support/releases/winnt/sr60cpci/onldoc/htmlfiles/gciptech/voip_ov7.htm
or help me to find more related documents about that
STFW :)
H.245 tunneling is needed if a firewall or NAT router would otherwise block a separate H.245 TCP connection.
However, sometimes a proxy or NAT router that is H.323 aware but is not a proper implementation won't handle H.245 tunneling.
Fast Start is a related feature, in that data normally transmitted via the H.245 connection is included in Setup and the response to it.
Sometimes Fast Start is needed, because a separate H.245 connection won't work, but tunneling won't work, either. In this case, features such as transfer, forwarding, etc. cannot be used.
Sometimes Slow Start is needed, because the endpoint or some intermediate proxy or router doesn't handle Fast Start properly.
In theory, H.245 tunneling and Fast Start are only used when both ends agree, but sometimes having mismatched settings causes trouble.
Most endpoints have independent options for Fast Start and tunneling; all four combinations are sometimes useful. Some endpoints have separate options for requesting Fast Start on outgoing, and accepting Fast Start on incoming. If several combinations work correctly, setup time is usually much faster with Fast Start on, and a little bit faster with tunneling on.
Some brain-dead endpoints insist on call progress audio if Fast Start is used -- you just get silence if the called end sends Alerting without audio.
Some brain-dead endpoints refuse to play call progress audio if Fast Start is not used -- you just hear ringing even if the called end would be sending an audible busy signal!
If anyone tells you that H.323 is a "standard", don't believe them ;)
Not that SIP is any better.
--Stewart
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