RE: H.324 ,H.320, H.323 phones

Jason Williams (
Tue, 2 Jun 1998 05:10:20 -0500 (CDT)

On Mon, 1 Jun 1998, oz wrote:
> Rolf...
> Could I impose upon you to explain -a little- as to why there are three
> H.32X standards when, from what you dscribe as to what they apply to,
> only the connection differs from one standard to next. In otherwords,
> I guess I would have expected the underlying transport machinery to
> pretty much not matter alot to the higher level layers of video conferencing,
> unless it wasn't a layered architecture in the first place.

I'm not's my guess :)

Since the mediums of ISDN, POTS, and LANs/Internet connections are quite
different in nature, they have different characteristics. I recall
reading ISDN has much lower latency time than a modem on the Internet.
POTS is completely different since there is very little delays in
transmission (There's not really any packet loss as is in the Internet).
My only guess is that the protocols take advantage of the characteristics
to maximize thruput and efficiency, etc. of the different mediums. I
always thought the layered idea worked great for internet protocols, but
when you have drastically different conditions to work under, protocols
tend to change to exploit the conditions. But since I haven't really
looked at the H.32X from the ITU, I'm not really sure.

And they do all fall under the H.32X category :)

--    * Jason Williams -- Austin, Tx.  |     |       * University of Texas at Austin  | ___ |         * BS Computer Science             \_|_/
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