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Re: ATM cell scrambling

  • From: albert.e.manfredi@boeing.com
  • Date: Mon, 24 Jan 2000 16:33:20 GMT
  • Organization: Boeing North American
  • X-Article-Creation-Date: Mon Jan 24 16:33:20 2000 GMT


In article <86hsvf$j1c$1@nnrp1.deja.com>,
  sripriyar@my-deja.com wrote:
> Hello Everybody,
> What is the practical application of cell scrambling on links below
DS3
> speeds? (I.432 does not define the application of ATM over these
> physical interfaces whereas it does for SONET and DS3.) Do DSL, T1 and
> E1 links require that this scrambling be applied?
>
> How extensively is ATM cell scrambling used in the real world?

ATM and SONET each uses scrambling rather than other methods (such as
4B/5B or Manchester encoding) to minimize DC bias. Which means that ATM
over SONET scrambles twice. Using scrambling, you avoid having a clock
rate that is faster than the bit rate. One symbol over the wire is one
bit of information.

So there is no issue with link speed. I expect that when we do send ATM
cells over DSL, the bits will be scrambled over DSL, as they are over
other media. Maybe someone has a different view?

--
Bert
albert.e.manfredi@boeing.com


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