Why an optical PHY makes 10GbE a non-LAN protocol

[Roy Bynum <rabynum@xxxxxxxxxxx>]

Peter,

I have been trying to figure out what the distinction between a LAN protocol and
others.  There was the "assumption" made with the development of 1000BaseLX that the
moderate power and 13xx wavelength specification would made it a MAN protocol. It
did not, it only opened the door for it to no longer be a LAN only protocol.  In
optical networking with optical PHYs, there is no such thing as a distiction between
a MAN and a WAN protocol, only between LAN and non-LAN protocols.

In re-thinking the distiction between the protocols that are restricted to short
distances, and those that are not, I may have found the answer.  Direct responce
protocols, such as ESCON have a specific acknowledge responce time on each data
block.  The transaction concurrency responce time of ESCON resticts it to a limited
distance.  The IBM standard has some specific distance limitations to it.  That
specific distance limitation, based in data block acknowledge responce time, limits
ESCON to being a LAN standard.  Changing the PHY by making it optical with high
launch power will not make into a WAN protocol, because the limitation is not in the
PHY, it is in the protocol itself.

Because of the latencies involved with the slow responce time of end systems and
mulitiple segments linked with repeaters, the original 802.3 did not have
restrictive frame acknowledge responce times.  At the time, 802.3 was distance
limited by the distances of coax cable. When full duplex 10BaseT came into being,
802.3 became a point to point protocol, not much different from any other point to
point protocol.  Some vendors even developed optical conversion and bridge
interfaces that were optical.

When 802.3 was increased to full duplex 100 mb speeds and given an optical PHY, the
distance limitations were offically removed.  Full duplex 100BaseSX is a non-LAN,
point to point protocol.  Some people even implemented 100BaseSX as in a MAN
configuration using optical wavelength converters.  Only economics and access to
long distance fiber prevented 100BaseSX from becoming a WAN protocol at the very
first.  Full Duplex 1000BaseLX offically gave sanction to non-LAN 802.3.   With
optical wavelength converters, even 1000BaseSX does not have any LAN distance
limitations.  Only the "assumption" that 802.3 was a LAN protocol did not allow the
802.3 WG to reconize that they were creating a non-LAN standard.

The lack of restrictive frame acknowledge responce timers will also make serial
optical 10GbE a non-LAN protocol by default.  Optical amplifiers will allow
implementations of 10GbE that will go at least 600km.  In the optical networking
environment there is no difference between a MAN or WAN at the protocol level.
Because of physical installation limitations, multi-fiber, parallel, MMF, 10GbE may
be a LAN only implementation.  In spite of the "assumption" that 802.3 is a LAN
protocol, serial optical 10GbE will not be.  Serial optical 10GbE will be a MAN/WAN
protcol.

Thank you,
Roy Bynum,
Optical and Data Network Technology Development
MCI WorldCom

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