H.323 Overhead
Stephen Casner
casner at CISCO.COM
Fri Feb 11 12:21:13 EST 2000
On Fri, 11 Feb 2000, Francois Menard List Account wrote:
> In terms of the overhead related to
> packets transmission, it is RTP encapsulation which is causing a lot of
> overhead.
Actually, the 12 bytes of RTP aren't the biggest part. There's also 8
for UDP, 20 for IP, and some more for a link-level header. But the
IP/UDP/RTP part can be compressed down to a few bytes across links
where that matters.
This compares to the H.221 overhead for H.323 -- I don't know that number.
But in the IP case, you also gain from silence suppression, which I
believe is only done on specialized links in the circuit case.
In my opinion, the focus on transmission overhead is misguided. If
you believe predictions that voice bandwidth will be a small fraction
of the converged IP network, then that overhead in the backbone should
not be an issue. Header ompression can be used on narrow links at the
edges.
-- Steve
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