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RE: 1000BASE-T PCS question


I think all the BER being discussed in the reflector is for exchange of
opinions from variety of disciplines.  These valuable opinions from
everyone, which are non-binding opinions, can be further used for the
discussion in future meeting to form up specification eventually.

If you listen to all the opinions, depending on your application, to someone
BER is irrelevant; however, to another one, BER is the key of the
performance specification.  The result is a compromised specification. 

Ed Chang 



-----Original Message-----
From: Rich Seifert [mailto:seifert@xxxxxxxxxx]
Sent: Friday, May 28, 1999 2:53 PM
To: Jaime Kardontchik; Chang, Edward S;
Subject: Re: 1000BASE-T PCS question

At 9:11 AM -0700 5/27/99, Jaime Kardontchik wrote:
>My impression is that it would have been much more simpler if the group had
>been called "10-Gigabit-Ethernet" instead of "Higher-Speed Group". At some
>time in the future the group will have to decide what kind of standard to

Well, it was not clear at all (and still is not clear) that a single-speed
10 Gb/s is the goal of all of the study group members, or indeed reflects
the needs of the user community. It is one of the purposes of the Study
Group to determine what speed(s) should be supported in a standard.

>Ethernet standards deliver a BER of 10^(-10).

This is simply not true. The BER spec for 10BASE5 is 10^-9. For 10BASE2 and
10BASE-T, it is 10^-8. For 100BASE-X and 1000BASE-X, it is 10^-12.

The BER goals for any higher-speed standard should be determined by the SG.
Further, BER is really a parameter more relevant to serial transmission
systems that do not use any block-coding; in such systems it is
straightforward to map between the BER and the Frame Loss Rate (a more
significant parameter in a connectionless, best-effort frame delivery
system). We had long discussions both in Fast Ethernet and 1000BASE-T about
how many frame errors are generated by a single bit error, the relationship
between symbol errors and bit errors, etc. In the end, the only observable
characteristic at the MAC service interface is the Frame Loss Rate. I
propose that any future standards work use this parameter to characterize
the error performance of the system, rather than BER.

Rich Seifert                    Networks and Communications Consulting
seifert@xxxxxxxxxx              21885 Bear Creek Way
(408) 395-5700                  Los Gatos, CA 95033
(408) 395-1966 FAX
"... specialists in Local Area Networks and Data Communications systems"