Re: Long distance links
Rich,
If someone wants to have an expensive LAN only PHY, I will not object. I just object to the
assertion that the WAN compatible PHY can only be more expensive than a LAN only PHY at the same
laser output. It may be more expensive, then again, maybe not. Based on the higher data rate
and the block encoding, the proposed LAN only PHYs will have a much higher total signaling rate.
Based on that issue only, the proposed LAN only PHYs will be more expensive.
Thank you,
Roy Bynum
MCI WorldCom
Rich Taborek wrote:
> 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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