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Re: Long distance links

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)


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

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


Best Regards,

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    
Palo Alto, CA 94303-4305    Alt email: rtaborek@xxxxxxxxxxxxx