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