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

Forwarded from Ben Brown.

Date: Mon, 01 Mar 2004 11:24:59 -0500
From: Benjamin Brown <>
Subject: Re: [EFM] Changes to 100BASE-X and 1000BASE-X PCS, 10G RS


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
That doesn't mean system companies can't continue to build ports with
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).
 >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