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RE: [EFM] Changes to 100BASE-X and 1000BASE-X PCS, 10G RS

Forwarded from Piers Dawe.

Subject: RE: [EFM] Changes to 100BASE-X and 1000BASE-X PCS, 10G RS
Date: Mon, 1 Mar 2004 20:22:43 -0000
From: <>
To: <>
Cc: <>, <>


There is stuff in EFM that is just too good to be pigeon-holed into the relatively small and new 
"Ethernet for access networks" market.  EFM has done good things which the large market of general 
IT/industrial/core/metro "legacy" Ethernets should be able and positively encouraged to take 
advantage of, within the 802.3 of the future, and with true compliance.

In particular, the future 802.3 will allow a consistent physical infrastructure (fiber cable) that 
can be upgraded 100-fold from 100 Mb/s to 1 Gb/s to 10 Gb/s, with a consistent maximum reach of 10 
km on SMF.  That's so much better for network operators than having to revisit link lengths, cable 
types and attenuations whenever considering an upgrade.  D3.1 Clause 66 presently tries to make this 
hard to do by asking for currently non-compliant PCSs.

Even if the EFM group appears to be relaxed about this rules change for PCSs, 802.3 at large should 
not.  The optics company doesn't forbid non-standard uses of its optics, but it does want the 
standard uses to be branded as standard so that IT departments everywhere can take advantage of our 
work without having the special knowledge needed to read between the lines.

If you think the systems companies and users will do the right thing and carry on building ports 
with legacy PCSs and 100BASE-LX10, 100BASE-BX10 and 1000BASE-LX10 optics anyway, we end up at the 
same conclusion: the standard should say the right thing.  Which has to be, treat 100BASE-LX10 the 
same as 100BASE-FX, treat 1000BASE-LX10 the same as 1000BASE-LX.

This isn't just about names, it's about meeting objectives, recognising the good stuff, and the need 
for careful review of the PCS changes.  Retrospective rules changes are not good.


 > -----Original Message-----
 > From: Benjamin Brown []
 > Sent: 01 March 2004 16:25
 > To: DAWE,PIERS (A-England,ex1)
 > Cc:;
 > Subject: Re: [EFM] Changes to 100BASE-X and 1000BASE-X PCS, 10G RS
 > Piers,
 > Your concern appears to be over the marketing of the
 > GBIC/PMD-type devices.
 > 100BASE-LX10, 100BASE-BX10 and 1000BASE-LX10 are all names of
 > PHYs, not optics. If an optics company can build optics that
 > work in both a
 > 1000BASE-LX PHY and a 1000BASE-LX10 PHY and they adverti$e the
 > optics as such, then they're not wrong if a system company
 > misnames the PHY.
 > Today, common optics are built for multiple technologies (FC,
 > GE, SONET).
 > It is not the concern of the optics company how their optics are used
 > and what
 > name is applied to the port type.
 > The majority of the group appears to be comfortable with
 > requiring the
 > PCS to
 > be capable of unidirectional operation  in order to use the
 > new EFM PHY
 > names.
 > That doesn't mean system companies can't continue to build ports with
 > different
 > or a limited set of capabilities. They just can't rightly
 > call them by
 > the new EFM
 > PHY names.
 > Ben
 > wrote:
 > >IEEE P802.3ah D3.1 proposes changes to:
 > >	PCS and PMA sublayer, 100BASE-X.  See 66.1 and 24;
 > >	PCS and autonegotiation, 1000BASE-X.  See 66.2 and 36 and 37;
 > >	RS for 10Gb/s.  See 66.3 and 46.
 > >and associated changes to management.
 > >
 > >(There's also a great deal of new, good stuff which is in
 > addition to the current 802.3, rather than having the effect
 > of modifying it.)
 > >
 > >The changes may have the unfortunate effect of changing some
 > existing implementations to being non-compliant with 802.3.
 > They might cause interoperability issues (need more reviewers
 > to establish if they do or don't).
 > >
 > >Examples:
 > >
 > >The well established practice of using 100BASE-X silicon
 > with OC-3 like optics, called something like "Fast Ethernet
 > on single mode fiber", which 802.3ah is meant to be
 > standardizing under the name of 100BASE-LX10, now might fall
 > foul of an effectively retrospective change, in which
 > P802.3ah D3.1 says the PCS and PMA should support currently
 > forbidden behavior.
 > >
 > >The 100 Mb/s bidirectional link type, standardized as
 > TS-1000 by TTC and as G.985 by ITU-T, uses the current 802.3
 > PCS/PMA and a PMD compatible with 100BASE-BX10 - a PCS/PMA
 > change would cause fragmentation and confusion.
 > >
 > >P802.3ah has objectives:
 > >	1000BASE-LX extended temperature range optics, and
 > >	1000BASE-X up to 10km over SM fiber,
 > >with the intention of bringing standardization with its
 > associated benefits to the widely used "stretched
 > 1000BASE-LX" or 1000BASE-LH; the to-be-standardized PMD type
 > being called 1000BASE-LX10.  But D3.1 says the PCS should
 > support currently forbidden behavior for 1000BASE-LX10, while
 > it says such behavior is to be optional for 1000BASE-LX or
 > 1000BASE-SX.
 > >As 1000BASE-LX and 1000BASE-LX10 are interoperable by design, and
 > >as a particular GBIC could be sold as compliant to
 > 1000BASE-LX or 1000BASE-LX10 while being identical, and
 > >as pluggable optics means that any user can swap between
 > 1000BASE-LX, 1000BASE-LX10, 1000BASE-SX and even 1000BASE-T,
 > >it is impracticable to demand different, unfamiliar,
 > behaviour from the PCS, according to the paperwork associated
 > with a probably pluggable, hot-swappable module.
 > >It is not yet clear whether this causes an interoperability
 > problem (need to understand how link starts up and reacts to
 > faults with Cl.37 autonegotiation on just one end) but it IS
 > clear that this is a market problem, making a retrospective
 > change to 1000BASE-X PCS requirements and tending to fragment
 > the market and/or weaken the validity of 802.3.
 > >
 > >The modified 10G RS may cause interoperability problems
 > interworking with current compliant 10G RS (I doubt this last
 > one, but we need representatives from the 10G community to
 > say yes, we have read this, understand the implications, and it's OK.)
 > >
 > >At the last 802.3ah meeting we spent some hours
 > investigating these issues, and learnt quite a lot of
 > detailed points.  The committee was not willing to make
 > significant changes to the draft at that time.  The problems
 > remain, and the clock is ticking; we should get to the bottom
 > of the issues, clean up the problems, and progress 802.3ah.
 > >
 > >Therefore, I urge particular review of the subclauses
 > mentioned above so that we don't go round in circles at the
 > meeting, 15-18 March.  The comment deadline is midnight EST,
 > Wednesday 3 March.
 > >
 > >Thank you,
 > >
 > >Piers Dawe
 > >
 > >
 > --
 > -----------------------------------------
 > Benjamin Brown
 > 178 Bear Hill Road
 > Chichester, NH 03258
 > 603-491-0296 - Cell
 > 603-798-4115 - Office
 > -----------------------------------------