H.323 Overhead

[Stephen Casner]

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