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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.

(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.

Best Regards,

At 14:39 00/04/07 -0500, Roy Bynum wrote:
> 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 -----

At 15:42 00/04/07 -0400, David W. Martin wrote:
> 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 
> for more background. Thank-you. 
> ...Dave