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Re: Clock Tolerance and WAN PHY


You have a very good a presenting that would seem reasonable to those who 
don't have any experience in attempting to implement what you are 
proposing.  The objectives of P802ae include a WAN PHY.  What constitutes a 
WAN PHY has been explained to the group by those of us that have worked in 
a WAN optical environment.  You keep miss representing the requirements of 
a WAN PHY by presenting a LAN implementation as a WAN.  It works very well 
at confusing those that are attempting to gain an understanding of what the 
issues are.

Those of us that have worked in the WAN optical environment are not 
confused by your comments.  Those of us that have worked in the WAN optical 
environment would like to have the opportunity to educate those that would 
actually like to gain a understanding of what the real world requirements are.

Thank you,
Roy Bynum

At 06:39 PM 1/24/01 -0800, Rich Taborek wrote:

>I strongly agree with your suggestion below, and Brad Booth's note along
>the same vein, to leave any conversion between Ethernet and SONET at the
>ELTE level. This would allow the LAN PHY, Serial or WWDM, it doesn't
>really matter since the ELTE does the required conversion, to natively
>serve LAN, MAN and WAN applications at the lowest possible cost. At the
>same time, the same LAN PHY can attach to an ELTE and operate in "WAN
>PHY mode" to support SONET/SDH. The latter would be applicable to those
>legacy SONET/SDH core applications, again, AT THE LOWEST POSSIBLE COST.
>Of paramount importance to the customer is our ability to meet the
>Economic Feasibility PAR criteria. In a nutshell this criteria states
>that the cost of 10GE shall be ~3.5X the cost of Gigabit Ethernet at
>product maturity. I don't visualize copying SONET/SDH, requiring +/-20
>PPM clock tolerance, supporting overhead bytes, etc. as helping us meet
>our economic feasibility objectives. However, I do see straightforward
>mappings, the same clock tolerances as Gigabit Ethernet (+/-100 PPM),
>protocol simplicity, relaxed jitter specifications, etc. as meeting the
>objectives. The latter are characteristics of the LAN PHY, the former
>are characteristics of the WAN PHY.
>Ethernet has met its economic feasibility objectives for three
>generations through selection and leverage of low cost physical layers.
>This will happen again through simple extension of Gigabit Ethernet
>physical layer technology as is the case for the LAN PHY. It should be
>obvious to the most casual observer that the more that SONET/SDH is
>leveraged for 10GE, the higher the total 10GE solution cost will be.
>Just reading though the notes of this thread, it looks like there's
>about as many ways to map Ethernet to SONET as there are to skin a cat.
>Here are some of the ones from this thread:
>1) Ethernet over LAPS, ITU-T SG7
>2) Packet over SONET, ???
>3) Ethernet over SONET/SDH, ITU-T SG7 X.86
>4) Ethernet over SONET/SDH, T1X1
>5) Digital Wrapper, ITU-T ???
>6) G.709, ITU-T (Same as Digital Wrapper???)
>7) IEEE P802.3ae WAN PHY
>I'm kind of partial to Ethernet over Ethernet.
>Best Regards,
>Boaz Shahar wrote:
> >
> > MAC - (Serial lan phy) - ELTE - (sonet ring) - ELTE - (serial lan phy) 
> - MAC
> >
> > Anyway, the WIS takes 64/66 frames and encapsulates them into the SONET
> > frame. So just take the 66/64 bit stream that comes to the ELTE through the
> > serial LAN and do the same there with a full SONET compliancy. Is that
> > correct? What is the advantage comes from doing the WIS in the PHY? (The
> > rate is not a problem Just operate the MAC in SONET rate as you do anyway
> > and put the FIFO in the ELETE as you anyway have in the WIS)
> >
> > Thanks (Sorry for the long mail)
> > Boaz
>Richard Taborek Sr.                 Phone: 408-845-6102
>Chief Technology Officer             Cell: 408-832-3957
>nSerial Corporation                   Fax: 408-845-6114
>2500-5 Augustine Dr.        mailto:rtaborek@xxxxxxxxxxx
>Santa Clara, CA 95054