It's 25% in the other direction (125mbps).
But I'm thinking you already knew that?
DaveC
Tom Lisa wrote:
>
> So, does this mean it should really be called 80BaseTX/FX because of the
> 20% overhead introduced by 4B/5B? :)
>
> Prof. Tom Lisa, CCAI
> Community College of Southern Nevada
> Cisco Regional Networking Academy
>
>
> Priscilla Oppenheimer wrote:
>
> 4B/5B is a signal encoding scheme. It's used in 100BaseTX and
> 100BaseFX
> also, so it's rather important to know. I'm going to have all the
> gory
> details in an upcoming white paper at
> http://www.certificationzone.com.
> Here's quick preview.
>
> 100BaseFX uses Non Return to Zero, Invert on One (NRZI), as does
> FDDI.
> 100BaseTX uses a variation of NRZI called either NRZI-3 or Multiple
> Level
> Transition - 3 (MLT-3).
>
> A disadvantage of NRZI and MLT-3 is that a steady stream of zeros,
> not
> uncommon in data, is represented as no transition, which is
> indistinguishable from no signal or a dead link. Another problem with
> no
> transitions is that the phase-locked loop that the receiving station
> uses
> to recover the clock signal can drift. If enough drift is introduced,
> the
> station cannot accurately receive data. To avoid this problem, the
> physical
> coding sublayer (PCS) first encodes data using 4B/5B translation.
>
> With 4B/5B translation, each possible 4-bit pattern is assigned a
> 5-bit
> code. The PCS maps four-bit nibbles in the data into five-bit codes,
> and
> vice versa, using a 4B/5B translation table. Every 5-bit code has at
> least
> two transitions to ensure proper clocking.
>
> Isn't that fascinating! Just kidding! ;-)
>
> Priscilla
>
> At 09:51 PM 4/25/01, William Wong wrote:
> >Dear all
> >
> >I couldn't find any information on this. Can you guys tell me what
> is this?
> >
> >Thanks.
> >
> >William
> >FAQ, list archives, and subscription info:
> >http://www.groupstudy.com/list/cisco.html
> >Report misconduct and Nondisclosure violations to
> [EMAIL PROTECTED]
>
> ________________________
>
> Priscilla Oppenheimer
> http://www.priscilla.com
> FAQ, list archives, and subscription info:
> http://www.groupstudy.com/list/cisco.html
> Report misconduct and Nondisclosure violations to
> [EMAIL PROTECTED]
> FAQ, list archives, and subscription info:
http://www.groupstudy.com/list/cisco.html
> Report misconduct and Nondisclosure violations to [EMAIL PROTECTED]
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