Re: Long distance links
Roy,
I think you're missing the point that Dae Young is making in support of my comments. Yes
indeed the line coding for 100BASE-FX is different from 1000BASE-SX/LX. As a matter of fact,
we have two different line codings for 1000BASE standards. 1000BASE uses 4D PAM5 line coding,
1000BASE-SX/LX/CX uses 8B/10B.
For 10 GbE we have 4 groups of PHY proposals, with some groups having multiple individual
proposals. The point of my note was to PREVENT a direction to FORCE a SPECIFIC line code on
10 GbE PHYs, especially in the LAN. If a specific 10 GbE WAN PHY wants to support a specific
line code, go ahead and propose it. Just don't encumber 10 GbE PHYs in general with it.
Best Regards,
Rich
--
Roy Bynum wrote:
> Dae,
>
> The line coding for 100BaseFX is different from 1000BaseSX/LX, that did not prevent a
> change. Why should it prevent a change with 10000BaseXX?
>
> Thank you,
> Roy Bynum
> MCI WorldCom
> Dae Young KIM wrote:
>
> > Rick,
> >
> > Please allow me add to your comments.
> >
> > Rich Taborek wrote:
> >
> > > However, there is no need for
> > > any 802.3 activity to define such coexistence at 10 GbE Ethernet rates. Once the 10
> > > GbE standard is set, many efficient implementations which route 10 GbE to SONET will
> > > spring up.
> >
> > This is quite an interesting and appealing argument.
> >
> > > Paul's proposal specifically excludes most 10 GbE PHY proposals by requiring
> > > specific encoding and delimiter usage to the point of requiring that the Ethernet
> > > PHY = SONET OC-192 PHY. I don't believe that this is in the best interest of 802.3.
> >
> > I do also have some concern about the line of logics Paul has suggested.
> >
> > As far as I know MII data rate with concern to SONET is one thing and the Ethernet line
> > coding is another.
> >
> > According to my understanding of Paul' picture:
> >
> > MAC --(MII)-- 9.58Gbps --(backpressure)-- SONET Payload
> > -- Add SONET overhead -- SONET Line Coding(NRZ)
> > -- SONET line rate of 9.95Gbps
> >
> > OR
> >
> > MAC --(MII)-- 10.0Gbps -- 10GbE PHY w/ line coding
> > -- 10GbE line rate(;depends on the line code chosen)
> >
> > As I understand, we're arguing on the MII rate which sits above the PHY layer. In that
> > far, the decision on the line rate should not affect the choice of the 10Gbe PHY line
> > code.
> >
> > --
> > Regards,
> >
> > Dae Young
> > http://ccl.chungnam.ac.kr/~dykim/
-------------------------------------------------------------
Richard Taborek Sr. Tel: 650 210 8800 x101 or 408 370 9233
Principal Architect Fax: 650 940 1898 or 408 374 3645
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