Re: SONET/Ethernet clock tolerance
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@nortelnetworks.com
>> >
>> > ========================
>> >
>> > -----Original Message-----
>> > From: Bruce Tolley [SMTP:btolley@cisco.com]
>> > Sent: Friday, March 24, 2000 2:50 PM
>> > To: stds-802-3-hssg@ieee.org
>> > 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
>>2500-5 Augustine Dr. mailto:rtaborek@nSerial.com
>>Santa Clara, CA 95054 http://www.nSerial.com