Re: SONET/Ethernet clock tolerance
Hi Rich,
After replying to Mr Osamu, earlier I noticed some inconsistency in my
statement. If all overheads
(including POH) is getting stripped off and re-generated at the E-S joint
and if, Ethernet
Frame (including preamble) is SPE payload, where is the question of pointer
adjustment ?
This means that I have missed your original point. Could you please explain the
picture of data flow + mapping as the Ethernet packet moves to SONET frames
and vice-versa ?
Thanks,
Tripathi.
At 10:36 AM 3/28/00 +0900, you wrote:
>Tripathi,
>
>As I understand, your suggestion causes SONET Path Termination at the
>edge of SONET infrastructure. That will require 'Ethernet Path
>Terminating Equipment' in addition to 'Ethernet Line Terminating
>Equipment' to re-write B3 Bit-Interleaved Parity byte.
>
>Regards,
>Osamu
>
>-----------------------------------------
>Osamu ISHIDA
>NTT Network Innovation Laboratories
>TEL +81-468-59-3263 FAX +81-468-55-1282
>-----------------------------------------
>
>At 9:20 AM -0800 00.3.27, Devendra Tripathi wrote:
> > Rich,
> >
> > My suggestion is that clock adjustment should happen on Ethernet side of
> > the "joint". The
> > reason is that IPG can be used to compensate for adjustments. This will
> > avoid any pointer
> > adjustments in SONET frames.
> >
> > Regards,
> > Tripathi.
> >
> > At 02:20 PM 3/25/00 -0800, you wrote:
> >
> >>Dave Martin, Norival Figueira,
> >>
> >>I've been looking at the various requirements for transporting Ethernet
> over
> >>SONET and one of them in particular is bothering me. That requirement is
> >>the one
> >>to bridge the clock tolerance of Ethernet (+/-100 ppm) with that of
> SONET (+/-
> >>4.6 ppm).
> >>
> >>The root question I have is whether or not current SONET framing or that
> >>proposed for the Ethernet WAN can accommodate a clock of +/- 100 ppm? This
> >>would
> >>be required to transport the proposed WAN PHY (or UniPHY) across clock
> domains
> >>tolerance. I'm asking this question because I'm trying to come up with a
> >>proposal for SONET framing for the UniPHY which is 100% compatible and
> >>compliant
> >>with SONET OC/192c and I am using all the WAN PHY information presented by
> >>yourself and others as a model.
> >>
> >>My understanding from a previous presentation by Paul Bottorff,
> >>http://grouper.ieee.org/groups/802/3/10G_study/public/july99/bottorff_1_
> 0799.pdf,
> >>slide 9, is that the payload clock tolerance is 320 ppm. Since I'm
> unfamiliar
> >>with the many nuances of SONET framing, can you please acertain that
> this is
> >>true?
> >>
> >>If the proposed SONET framing for Ethernet is adequate to support
> +/-100 ppm
> >>clock tolerance compensation, the second question I have is as to the
> >>mechanism
> >>for performing clock tolerance compensation. It seems to me that the
> mechanism
> >>involves at least the rewriting of SPE pointers and the modification of
> Line
> >>Overhead Bytes (H1 and H2).
> >>
> >>My further understanding is that the clock tolerance compensation
> process is
> >>referred to as one of the 3 "R's" (Re-Amplify, Re-Shape, Re-Time). The
> >>specific
> >>process is Re-Timing and is usually reserved to SONET Regenerators and
> LTE's
> >>(Line Terminating Equipment). It has been proposed that Transponders for
> >>coupling an Ethernet WAN PHY to SONET OC-192c can be either "Passive" or
> >>"Active" according to our agreed upon "WAN PHY Definitions":
> >>http://grouper.ieee.org/groups/802/3/ae/public/mar00/law_1_0300.pdf. My
> >>observation is that a transponder which contains both 100 ppm and 4.6 ppm
> >>optics
> >>MUST perform re-timing. Therefore, it must be an Active Transponder.
> This is
> >>also the case for all WAN PHY elements which cross clock domain boundaries.
> >>Please help me validate or invalidate my observations.
> >>
> >>If my observations are correct, my suggestion is to not bridge Ethernet to
> >>SONET
> >>until the SONET boundary is encountered. A WAN PHY, SONET Lite or
> UniPHY which
> >>transports SONET framed Ethernet in any manner may require significant
> >>re-framing at any point that retiming is required.
> >>
> >>
> >> > David Martin wrote:
> >> >
> >> > How about "SONET-compatible PHY". While I could agree to drop the "WAN"
> >> > portion of the name, we still need to be clear that our proposal is
> not a
> >> > SONET-compliant PHY. There is a significant cost/feature difference. To
> >> > reiterate,
> >> > the "SONET-compatible PHY" has the following key differences:
> >> >
> >> > 1. minimal OH processing (i.e. only 4 OAM bytes, not SONET's
> >> > 36-A1/2-H1/4=30)
> >> > 2. wider clock tolerance (i.e. the usual +/-100ppm, not SONET's
> >> +/-4.6ppm)
> >> > 3. higher jitter tolerance (i.e. >0.15UIpp of SONET, exact value
> >> still TBD)
> >> > 4. low cost optics (i.e. for <40km, not the 80/120km of SONET OC-192)
> >> >
> >> > All of which will "bring the cost down out of the stratosphere" to
> >> paraphrase
> >> > a
> >> > committee member and in line with the 3x1GE target.
> >> >
> >> > ...Dave
> >> >
> >> > David W. Martin
> >> > Nortel Networks
> >> > +1 613 765-2901
> >> > +1 613 763-2388 (fax)
> >> > dwmartin@xxxxxxxxxxxxxxxxxx
> >> >
> >> > ========================
> >> >
> >> > -----Original Message-----
> >> > From: Bruce Tolley [SMTP:btolley@xxxxxxxxx]
> >> > Sent: Friday, March 24, 2000 2:50 PM
> >> > To: stds-802-3-hssg@xxxxxxxx
> >> > Subject: Renaming the WAN PHY
> >> >
> >> > Colleagues:
> >> >
> >> > To follow up on the suggestion made by Jonathan during the New
> Mexico
> >> > plenary, may I be so bold as to suggest that we change the name
> of the
> >> > "WAN
> >> > PHY" to something very simple like PHY with SONET framer.
> >> >
> >> > We need to get the word WAN out of the name of the PHY
> >> >
> >> > o Most common folk outside the esteemed IEEE process think long
> >> distance
> >> > when they think WAN and on the basis of Paul Bottorf of Nortel,'s
> >> > presentations the initial application of the WAN PHY would be for
> >> short
> >> > links between collocated equipment often in the same room.
> >> >
> >> > 2) There are ways to build MANs/WANs that do not require SONET.
> >> For 10GbE
> >> >
> >> > some of these MANs/WANs will use the LAN PHY and a 1550 PMD
> over dark
> >> > fiber
> >> > or dark wavelengths. The proof point for this is the 1000s of long
> >> > distance
> >> > 1310 nm 1550 nm 1000BASE-X GBICs that are being deployed today
> >> over dark
> >> >
> >> > fiber. The WAN PHY as stated in the goal does not address the
> total
> >> > possible 10GBE WAN market and confuses people.. This makes it a
> >> bad name
> >> > in
> >> > my opinion
> >> >
> >> > I do not think we necessarily need a motion to change the
> >> objective, but
> >> > I
> >> > think we need to choose our words carefully when we name the PHY
> >> that the
> >> >
> >> > objective signifies.
> >> >
> >> > Bruce
> >> > Cisco Systems
> >>
> >>--
> >>
> >>Best Regards,
> >>Rich
> >>
> >>-------------------------------------------------------
> >>Richard Taborek Sr. Phone: 408-845-6102
> >>Chief Technology Officer Cell: 408-832-3957
> >>nSerial Corporation Fax: 408-845-6114
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