RE: What is 802.3ae WAN-PHY?

["David Martin" <dwmartin@nortelnetworks.com>]

Title: RE: What is 802.3ae WAN-PHY?

Osamu,

Some corrections to your table further below:

SONET, with full OH access, +/-20ppm minimum clock is defined in T1.105.
The T1.416 spec references T1.105 for clock tolerance/synchronization.
Our WAN-compatible PHY OH access is defined in:

http://grouper.ieee.org/groups/802/3/10G_study/public/nov99/figueira_2_1199.pdf

and uses the +/-100ppm Ethernet clock tolerance. Per an earlier e-mail, I'd
strongly recommend we stop using the term "SONET-lite". As was once stated in
the OIF, there are as many interpretations of it as there are networking engineers.

...Dave

David W. Martin
Nortel Networks
+1 613 765-2901  
+1 613 763-2388 (fax)
dwmartin@nortelnetworks.com

========================

-----Original Message-----
From:   Osamu ISHIDA [SMTP:ishida@exa.onlab.ntt.co.jp]
Sent:   Sunday, April 09, 2000 3:06 AM
To:     Roy Bynum; Martin, David [SKY:1I63-M:EXCH]
Cc:     stds-802-3-hssg@ieee.org
Subject:        Re: What is 802.3ae WAN-PHY?

Hi Roy, Hi Dave,

Thank you for your feedback.  Your comments are helpful for me to
understand what was going on in HSSG and T1, since I have joined
HSSG since the Dallas meeting (Jan. 2000) and I have no liaison
to T1.

Before discussing in detail, I think we had better be aware once
again that here is a LAN community, and keep in our mind that we
should be much careful to use WAN terminology.  I use the
following definitions in this mail; please let me know if there
is any inconvenience to you.
 --------------- --------------- ------------ ----------- ------
 expression      Overhead access CLK Accuracy CLK Jitter  Std.
 --------------- --------------- ------------ ----------- ------
 SONET           (almost) full   < +/-20ppm   SONET spec. T1.105
 SONET-compliant reduced         < +/-20ppm   SONET spec. T1.416
 SONET-lite      much reduced    < +/-100ppm  ??????????  ??????
 --------------- --------------- ------------ ----------- ------
 Here I assume that SONET-lite equals WAN-PHY with SONET framer
 proposed in 802.3ae.

I think we can agree on the following two facts;

 (1) There is no SONET-lite standard at present.  All SONET or
     SONET-compliant equipment at present, including the emerging
     non-muxing LTE, should meet +/-20ppm CLK accuracy and SONET
     jitter spec.

 (2) Pointer manipulation mechanism in SONET framer itself has
     the potential to accommodate the CLK difference up to +/-320ppm.

According to Roy, there are some discussions on relaxing the SONET
CLK accuracy for some specific applications in T1 or ITU-T.  That's
news to me; please let me know where I can get the more information
about the discussion.

I have no authority to decide how NTT reacts in ITU-T, but I will
strongly recommend my colleagues who often attend the ITU-T expert
meeting not to approve such standard proposals.  The reasons are;

(1) I know we have at least one SDH system that raises an alarm for
    too many pointer re-writing to indicate wrong CLK accuracy.

(2) It can not be connected to SONET regenerators.  This implies
    that it is not a SYNCHROUNOUS system any more.  I see no reason
    to define 'plezioisosynchronous' system with SONET framer which
    is optimized for SYNCHRONOUS systems.  Note that we have a
    serious trade-off between CLK accuracy and jitter transfer in a
    SONET regenerator (you can read it in SYNCHRONUS transport systems). 
    I think this is what Erik has pointed out in his recent comment.
http://grouper.ieee.org/groups/802/3/10G_study/email/msg02157.html

(3) I'm afraid that it would nominate the client path; only OC-192c
    or some small variations could be carried through non-muxing LTE.
    We will lose flexibility to accommodate any combination of OC-1,3,
    12,48,192.  Or we require very heavy Line terminating circuit to
    re-write up to 192 pointers independently.

Above consideration tells me that, if we use the SONET framing,
we had better keep +/- 20ppm accuracy to be compliant to SONET.
Then it can be connected directly to existing SONET regenerators and
WDM active transponders.  We don't need to pay the SONET-framing
charge twice for WAN-PHY and ELTE.  And again, I don't believe
SONET regenerator for 10GbE is a good choice unless you have already
invested in it.
http://grouper.ieee.org/groups/802/3/10G_study/email/msg01869.html

Best Regards,
Osamu

At 14:39 00/04/07 -0500, Roy Bynum wrote:
http://grouper.ieee.org/groups/802/3/10G_study/email/msg02169.html
>
> Osamu,
>
> "SONET Lite" is a term that has been used for some time to mean a reduced
> overhead requirement customer drop interface.  T1.416-99 defines the
> required and optional byte usage for "SONET Lite".  The plezioisosynchronous
> timing standard is currently being worked on.  It should be a full standard
> definition very soon.  In this regard, the "ELTE" is acutely a special case
> non-muxing LTE that is part of the T1X1 standards.  The SONET test sets that
> are used for POS today already have to be adjusted to allow for wider clock
> and jitter tolerance.
>
> Thank you,
> Roy Bynum
>
> ----- Original Message -----
http://grouper.ieee.org/groups/802/3/10G_study/email/msg02164.html

At 15:42 00/04/07 -0400, David W. Martin wrote:
http://grouper.ieee.org/groups/802/3/10G_study/email/msg02170.html
>
> Osamu,
>
> Our WAN PHY proposal uses the traditional +/-100ppm clock tolerance spec
> of Ethernet.  An ELTE would have a matching WAN PHY interface. The SONET
> side of the ELTE will have an ITU/ANSI interface. Within the ELTE the clock
> domain adaptation is performed using traditional SONET pointer processing.
> Previous material has shown this is feasible. Please refer to
>
> http://grouper.ieee.org/groups/802/3/10G_study/public/july99/bottorff_1_0799.pdf
>
> for more background. Thank-you.
>
> ...Dave