Autonegotiation @ 100 / 1000BASE-T - why in another sublayer of PHY

Hello,

little question, that does not find it's answer in google (no matter of what
angle I strike it) - in 100BASE-TX, autonegotiation function is placed just
before the RJ-45 (MDI), under the PMD (physical medium dependent - at the
bottom of PHY), and then - in 1000BASE-T it is defined as a functional block
of PCS (physical coding sublayer - at the top of PHY).

Simple q: W H Y ? ? ?

Does anyone has an answer? Or does anybody has skills to dig this simple
info from the web?

thanks in advance,
banan

banan <(E-Mail Removed)> wrote:
> little question, that does not find it's answer in google (no matter
> of what angle I strike it) - in 100BASE-TX, autonegotiation function
> is placed just before the RJ-45 (MDI), under the PMD (physical
> medium dependent - at the bottom of PHY), and then - in 1000BASE-T
> it is defined as a functional block of PCS (physical coding sublayer
> - at the top of PHY).

> Simple q: W H Y ? ? ?

I'm not sure it is an/the answer, but autoneg in 100BT was (at least
initially) optional. I don't think it was ever optional in 1000BT.
Perhaps that has something to do with where it is placed? I suspect
the folks over in comp.dcom.lans.ethernet would know.

rick jones
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