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Cell Relay Retreat>List Archive>month:1998-Jan> msg00000



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Re: 155Mbs and Full Duplex

  • From: George Marshall <george@marshalls.org>
  • Date: Thu, 01 Jan 1998 17:34:57 -0800

Charley Kline wrote:
> 
> George Marshall <george@marshalls.org> writes:
> ...
> There's still IFG and preamble which do steal some of the useful
> bandwidth.
> 
> OC-3 over SONET uses 8B10B coding so the actual signalling rate on the
> medium is up around 200 Mb/s or so for 155Mb/s of data, only 48/53rds of
> which or about 140 Mb/s or so is usable payload. The various AAL's eat
> into that further.

Slight correction on the coding .... there is indeed an ATM Forum
physical interface which uses 8B10B encoding and operates at a data rate
of 155.52 with a ~200 Mb baud rate.  However, its not OC-3/SONET, which
does not use a baud-expanding encoding.

George Marshall

--
george@marshalls.org