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

["Perkins, Drew" <drew.perkins@lightera.com>]

I think that we need new terms. I don't know what they should be, but
LAN/WAN/MAN/SAN/xAN are too overloaded. The critical difference between LAN
and WAN has never been just the distance between two communicating
endpoints. As I said previously, I believe the critical differentiator is
whether or not the protocol has tools to allow a 3rd party service provider
provide a managed L1 transmission service between two points.

Even if Gigabit Ethernet is being used over private fiber end-to-end across
Canada, that doesn't mean that it has the tools that many service providers
want in order to provide an easily-managed, robust communications service.

Drew
---------------------------------------------------------
Ciena Corporation                 Email: ddp@lightera.com
Core Switching Division                 Tel: 408-865-6202
10201 Bubb Road                         Fax: 408-865-6291
Cupertino, CA 95014              Cell/Pager: 408-829-8298


-----Original Message-----
From: owner-stds-802-3-hssg@majordomo.ieee.org
[mailto:owner-stds-802-3-hssg@majordomo.ieee.org]On Behalf Of Rich
Taborek
Sent: Tuesday, June 29, 1999 3:32 PM
To: rabynum@airmail.net; HSSG
Subject: Re: Why an optical PHY makes 10GbE a non-LAN protocol



Roy,

I know that you have made several arguments to the point that Gigabit
Ethernet is
not a LAN because of its 1000BASE-LX variant which supports extended
distances. I'd
like to respond with some relevant history which I am personally familiar
with:

Way back in 1988 or so (+ or - one year) I was working at IBM designing
mainframe
channels. One of the neatest products I've had the opportunity to work with
at the
time was a 3044 Channel Extender. This product consisted of two physical
boxes, one
connected to the Bus and Tag cables of a mainframe channel interface, the
other
connected to the Bus and Tag cables of the first in a series of peripheral
devices,
other devices being daisy chained to the first device. A fiber optic cable
connected
the two 2 3044 units. In this fashion the existing 120 meter Bus and Tag
cable limit
could be extended to 2 km over 62.5 um MMF and 3 km over 50 um MMF. The line
rate
was 200 Mbps, the encoding was 8B/10B, and the transmitter was an LED. The
3044 was
an excellent technology evaluator for IBM's current fiber optic-based
mainframe
channels dubbed ESCON (TM). ESCON channels, first introduced in 1990 and the
current
workhorse, use the same basic PHY but different framing than the 3044
channel
extended. One other significant addition is that ESCON channels also
supported a
laser-based PHY variant, extending the supported ESCON distance to 20 km
with a 1300
nm laser source. Up to three links could be arranged in line through two
switches,
forming a 60 km link between mainframe channel to peripheral.

Other LAN protocols like FDDI supported similar extended LAN distances.
Fibre
Channel broke the 1 Gbps barrier with a completed standard in 1994,
supporting
distances of up to 10 km in ANSI X3.230-1994 (FC-PH). The GbE 1000BASE-X PHY
is
based upon the FC-PH PHY.

The point in all the prior rambling is the GbE was not the first to venture
into the
extended LAN (call it MAN or WAN, whatever) space. Other proprietary or
standard
solutions may have gotten there earlier than even the 3044. I'm sure that
the IEEE
802.3 has no shortage of communications systems historians.

Existing LAN and SAN data communications protocols including Ethernet, FC,
HIPPI,
FDDI have done more than extremely well at meeting the needs of the
environments for
which they were designed from a cost, functionality, reliability,
manageability,
operations, serviceability, configuration flexibility, salability (I could
go on and
on) point of view. The WAN marketplace, and perhaps the MAN marketplace as
well, is
new and unfamiliar territory to many from the LAN and SAN community.

I don't find it altogether unreasonable, that given the proper requirements,
guidelines, and historical perspective, that 10 Gigabit Ethernet can
assemble a
standard that addresses all LAN and extended LAN environments as did its
predecessors as well as venturing into the MAN and WAN space while
simultaneously
providing compatibility with all of the existing MAN and WAN infrastructure.

What's wrong with the above picture?

--

Roy Bynum wrote:

> ... (text deleted)

> 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
> > BLSR.
> >
> > Drew
> > ---------------------------------------------------------
> > Ciena Corporation                 Email: ddp@lightera.com
> > Core Switching Division                 Tel: 408-865-6202
> > 10201 Bubb Road                         Fax: 408-865-6291
> > Cupertino, CA 95014              Cell/Pager: 408-829-8298
> >
> > -----Original Message-----
> > From: owner-stds-802-3-hssg@majordomo.ieee.org
> > [mailto:owner-stds-802-3-hssg@majordomo.ieee.org]On Behalf Of Roy Bynum
> > Sent: Sunday, June 27, 1999 6:15 AM
> > To: Peter_Wang@3com.com
> > Cc: stds-802-3-hssg@ieee.org
> > 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
> >
> > >

--

Best Regards,
Rich

-------------------------------------------------------------
Richard Taborek Sr.    Tel: 650 210 8800 x101 or 408 370 9233
Principal Architect         Fax: 650 940 1898 or 408 374 3645
Transcendata, Inc.           Email: rtaborek@transcendata.com
1029 Corporation Way              http://www.transcendata.com
Palo Alto, CA 94303-4305    Alt email: rtaborek@earthlink.net