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

[Drew Perkins <drew.perkins@xxxxxxxxxxxx>]

Roy,
	I believe that the difference between LAN and WAN (including MAN)
protocols has been mentioned in another very recent note. The key difference
is whether or not it is the same administration that owns and operates both
ends of the communication as well as the media in between. This is typically
the case with LANs. WANs, on the other hand, are typically owned, operated,
and managed by a service provider. Because the service provider needs to
have good tools to know when they are not providing good service, and to
locate the problem causing bad service, and to restore service while there
is a problem, WAN protocols tend to have facilities to provide superior
OAM&P compared with LAN protocols. Flavors of Ethernet do not currently have
the mechanisms for providing these tools.

There may also be significant differences between MAN and WAN protocols. In
both the SONET/SDH worlds and DWDM worlds, the protocols used over MANs and
WANs may differ significantly. MAN protocols are often built to favor
simplicity and performance over efficiency. Hence the use of UPSRs. WAN
protocols are more often built to favor efficiency over simplicity and
performance due to the significantly higher costs. Hence the use of 4 Fiber
BLSR.

Drew
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-----Original Message-----
From: owner-stds-802-3-hssg@xxxxxxxxxxxxxxxxxx
[mailto:owner-stds-802-3-hssg@xxxxxxxxxxxxxxxxxx]On Behalf Of Roy Bynum
Sent: Sunday, June 27, 1999 6:15 AM
To: Peter_Wang@xxxxxxxx
Cc: stds-802-3-hssg@xxxxxxxx
Subject: Why an optical PHY makes 10GbE a non-LAN protocol



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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