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


What you are talking about are implementation differences, not L2 protocol
differences.  L2 protocols such as SDLC, PPP, etc., all have fairly long
acknowledge responce timers.  Closed loop protocols such as FDDI are less
forgiving, just as half duplex 802.3 was less forgiving.  Full duplex 802.3 acts
more like PPP in the regard of supportable link distance.

I have seen SDLC implemented over LAN facilities such as Token Ring.  It worked
just fine.  Does that make SDLC into a LAN protocol?  SDLC was often used as the
WAN protocol for Token Ring source route bridging.  Does that make SDLC a WAN
protocol?  These are implemenation issues.  What is it that makes SDLC a LAN or
a WAN protocol?  A WAN protocol has the ablity to work over extended distances;
a LAN protocol does not.  Does full duplex 802.3 have the ability to work over
extended distances?

This is a door that has already been opened.  802.3 was altered into an extended
distance, WAN, protocol by making it full duplex.  It may not have been the
intention of the 802.3 WG to do so, but that is what was accomplished.  Adding
an extended distance PHY sanctioned 802.3 for use over extended distances,
either over privately owned facilities, or over commercial services facilities.

I simply want to point out that what was accomplished by the 802.3 WG was
greater than what they intended.  They opened the extended distance, WAN, market
place to Native data, 802.3.  This is going to have more of a major impact on
long haul data communications that it will have on the LAN environment, which
already has Native data, 802.3.  The over all long term result will be lower
cost data communications over extended distances, WANs as well as LANs.

Thank you 802.3 WG,
Roy Bynum,
MCI WorldCom

Drew Perkins wrote:

> 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
> Drew
> ---------------------------------------------------------
> Ciena Corporation                 Email: ddp@xxxxxxxxxxxx
> Core Switching Division                 Tel: 408-865-6202
> 10201 Bubb Road                         Fax: 408-865-6291
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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
> protocol, serial optical 10GbE will not be.  Serial optical 10GbE will be a
> protcol.
> Thank you,
> Roy Bynum,
> Optical and Data Network Technology Development
> MCI WorldCom
> >