Hi all Would someone know the % of overhead in H.323 & H.320 Thanks for any help you can provide Chris Christopher Iles Senior Technologist COMMUNICATIONS RESEARCH CENTER e-mail: christopher.iles@crc.ca 3701 Carling Ave Tel office: 613 998 2734 Ottawa, Ont. K2H 8S2 Ops Room : 613 998 2374 ATTN: BLDG 46
As I said plenty of times before, 99% of the complexity of a telephone call placed using H.323 is due to H.323 itself. The overhead is in terms of complexity of the processing. In terms of the overhead related to packets transmission, it is RTP encapsulation which is causing a lot of overhead. -=Francois=- On Fri, 11 Feb 2000, Christopher Iles wrote:
On Fri, 11 Feb 2000, Francois Menard List Account wrote:
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
Chris, Each H.320 frame (ignoring optional encryption) is 640 bits (for clear channel) of which 16 bits are dedicated to FAS (Frame Alignment Signal) and BAS (Bit-rate Allocation Signal). 16 / 640 * 100 = 2.5 % overhead. See ITU-T H.221. Since H.323 overhead is based on payload size (which varies with codec output and network characteristics), more parameters are needed to calculate the overhead. See ITU-T H.225. A good, general source is "Videoconferencing and Videotelephony," Richard Shaphorst, Artech House, Inc., (c) 1996. Barry At 09:25 AM 2/11/00 -0500, you wrote:
participants (4)
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Barry Aronson -
Christopher Iles -
Francois Menard List Account -
Stephen Casner