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Re: Long distance links




All:

Certainly, the 300 m MMF is very significant distance for the WAN PHY since
it provides an interface for connecting components in TeraPOPs. As far as I
know the WAN PHY doesn't need to support backward compatibility with old
MMF, therefore we don't need the 100 m MMF for the WAN PHY. 

A good set of objectives for WAN PHY distance might be 300 m MMF, 2 Km SMF,
15 Km SMF, and 40 Km SMF. The 300 MMF distance would give the WAN PHY a low
cost VSCEL interface using high grade MMF cable. The 2 Km SMF matches the
WAN short reach distance. Moving the 10 Km SMF specification to 15 Km would
match the WAN intermediate reach specification giving support to the
installed base of IR WAN fiber. Perhaps the 40 Km SMF would be best
specified on for use on existing OC-192 lasers and using OC-192 clocking.
This would make the 40 Km reach capable of direct attachment to an OC-192
capable DWDM network.

Paul

At 02:17 PM 9/11/99 -0500, Roy Bynum wrote:
>
>Rich,
>
>I should have said 300m MMF short reach would be used quite a bit for the
WAN compatible
>PHY because of facilities collocation of the NSP systems with the metro
and long haul
>transmission/DWDM systems.  Thank you for correcting my understanding of
the current
>objective distances.
>
>Thank you,
>Roy Bynum
>MCI WorldCom
>
>Rich Taborek wrote:
>
>> Roy,
>>
>> HSSG objectives only specify a MMF distance of 300M. How to you intend
to meet the 500M
>> distance over MMF when operating at an OC-192 line rate? Do you have a
500M MMF WAN PHY
>> proposal available now or to present in York or Kauai?
>>
>> Note the Lucent has presented a brand new fiber with a
bandwidth*distance of 2200/500
>> MHz-km at 850/1300 nm with “laser” launch. This is one of the best
fibers I know of.
>> It'll get you out to about 440M at an OC-192 line rate with VCSEL. Note
also that this
>> is NEW not INSTALLED fiber.
>>
>> In my estimation, if you want an inexpensive 500M MMF interface which
connects a
>> customers LAN with DWDM equipment, you need to reduce the line rate with
a MAS, WWDM,
>> or Parallel Optics approach.
>>
>> Best Regards,
>> Rich
>>
>> --
>>
>> Roy Bynum wrote:
>>
>> > Rich,
>> >
>> > There are two different WAN specific implementation architectures.
One of these is
>> > to use one of the SMF PHYs.  The other uses a MMF PHY.  When going
into transport
>> > DWDM equipment at the customer or ISP POP site, the service providers
would like to
>> > save money by using inexpensive interfaces also.  The 500M MMF PHY is
also a WAN
>> > implementation.
>> >
>> > Thank you,
>> > Roy Bynum
>> > MCI WorldCom
>> >
>> > Rich Taborek wrote:
>> >
>> > > Paul Bottorff wrote:
>> > >
>> > > (text deleted)
>> > >
>> > > > Provided people built networks to this configuration, then it
works just
>> > > > fine.
>> > > > The IEEE has not yet decided to build 2 PHYs. I believe that the
WAN PHY
>> > > > being talked about does not have a distinct identity from the LAN
PHY.
>> > > > Because I don't have a good criteria for distinct identity I've
found no
>> > > > reason to believe the committee should build 2 PHYs. My assumption
is that
>> > > > any PHY developed may run on SMF and may be deployed in the wide
area. This
>> > > > is what is currently happening with 1 GigE.
>> > >
>> > > (text deleted)
>> > >
>> > > Paul,
>> > >
>> > > This is exactly what I'm concerned about. Your requirements to have
Ethernet
>> > > operate at a MAC/PLS rate of 9.58464 Gbps, perform encoding with NRZ
efficiency
>> > > (assumed to mean 0% overhead) and not use special symbols is
unreasonable and
>> > > in conflict with virtually all 10 GbE PHY proposals presented to the
HSSG to
>> > > date.
>> > >
>> > > The best criteria for distinct identity is cost. For example, we can
go through
>> > > all the components in a MAS PHY and all the components in your
proposed WAN PHY
>> > > if you like. ...All right... I'll tell you: A prototype MAS PHY
transceiver I
>> > > envision will use an SFF shell, a SFF connector, a MAS PHY CMOS chip
including
>> > > laser driver, one laser, one photodiode/aIA/Post-amp and operate at
5 GBaud
>> > > (2.5 GHz). The result will be a significant difference in cost with
a MAS PHY
>> > > coming out on top.
>> > >
>> > > Another criteria is distance. A MAS PHY at 5 GBaud will support a
MMF (all LANs
>> > > are MMF not SMF) distance of approximately 2X your proposed WAN PHY
given the
>> > > same optics (which BTW need to support half the bandwidth of a WAN
PHY and are,
>> > > therefore, less expensive.
>> > >
>> > > Another criteria is ease of implementation through the use of
integral clock
>> > > multiples in the most common 10 GbE equipment. That is, equipment which
>> > > supports multiple Ethernet data rates.
>> > >
>> > > I could go on...
>> > >
>> > > Many PHYs proposed for 10 GbE WILL NOT run over SMF. I'm probably
splitting
>> > > hairs here, but VCSELs in general support only MMF. Many of the 10
GbE PHY
>> > > proposals support VCSELs. Are you excluding VCSELs from supporting
10 GbE?
>> > >
>> > > I participated in the Gigabit Ethernet Standards process from day 0
till the
>> > > standard was published. There was never an objective set to support
the WAN nor
>> > > was there any discussion or work done on a separate WAN PHY. As you
and Roy
>> > > Bynum have pointed out, GbE is being successfully deployed in the
WAN without
>> > > even considering this environment. I'm wondering right now if the
HSSG should
>> > > do the same at 10 GbE?
>> > >
>> > > Your proposal for a single PHY to meet all HSSG objectives including
direct
>> > > support of the SONET WAN environment appears to be flawed from both a
>> > > cost/performance and simplicity perspective. 802.3 folks have
drummed these
>> > > basic tenets into my head since I joined the group trying to sell
them Fibre
>> > > Channel technology lock stock and barrel. I clearly changed my tune,
proving my
>> > > flexibility. We can start negotiating any time now :-)
>> > >
>> > > > Paul A. Bottorff, Director Switching Architecture
>> > > > Enterprise Solutions Technology Center
>> > > > Nortel Networks, Inc.
>> > > > 4401 Great America Parkway
>> > > > Santa Clara, CA 95052-8185
>> > > > Tel: 408 495 3365 Fax: 408 495 1299 ESN: 265 3365
>> > > > email: pbottorf@xxxxxxxxxxxxxxxxxx
>>
>> -------------------------------------------------------------
>> 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
>
>
Paul A. Bottorff, Director Switching Architecture
Enterprise Solutions Technology Center
Nortel Networks, Inc.
4401 Great America Parkway
Santa Clara, CA 95052-8185
Tel: 408 495 3365 Fax: 408 495 1299 ESN: 265 3365
email: pbottorf@xxxxxxxxxxxxxxxxxx