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

[Bruce LaVigne <bruce@xxxxxxxxxxx>]

Drew,
  I think I am hearing another differentiation as well (correct me if I
am wrong): it seems that in the WAN/MAN space, more customers buy their
setup from a single vendor, so proprietary things like FEC, coding
schemes, wavelength, WDM, etc. are less of an issue; whereas in the
LAN space, many customers may have multiple vendor's equipment, and
expect them to interoperate flawlessly (not that they always do ;-)

As such, the LAN standards are very stringent about the physical
interface, so that adhering to the standard should mean your equipment
interoperates -- plug one end of a cable into vendor A's device, and
the other end of the same cable into vendor B's device, and they work.
While there are proprietary "value adds", it's not usually at the PHY layer.
For example, a vendor may have a 1000Base-LX or SX or CX interface, but
there are few (if any) optical GE devices using a different coding
scheme than 8B10B, or WDM, etc. -- in the LAN space.  I am hearing that
in the WAN space, it is much more "anything goes" since a single vendor's
equipment will probably be on both ends of the cable.  Is this a correct
assessment?

-Bruce LaVigne


"Perkins, Drew" wrote:
> 
> 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@xxxxxxxxxxxx
> 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@xxxxxxxxxxxxxxxxxx
> [mailto:owner-stds-802-3-hssg@xxxxxxxxxxxxxxxxxx]On Behalf Of Rich
> Taborek
> Sent: Tuesday, June 29, 1999 3:32 PM
> To: rabynum@xxxxxxxxxxx; 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@xxxxxxxxxxxx
> > > 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@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
> > >
> > > >
> 
> --
> 
> 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@xxxxxxxxxxxxxxxx
> 1029 Corporation Way              http://www.transcendata.com
> Palo Alto, CA 94303-4305    Alt email: rtaborek@xxxxxxxxxxxxx