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[802.3ae] Re: Clarification of the 10GBASE-W ELTE function


Please read the specifications for the use of +/- 20 PPM clock for a 
"client" signal.  It is for maintenance (read "temporary") use only.  A 
non-bit stuffed client at +/-20 PPM still has too many clock offsets and 
pointer adjustments to be stable from and "Ethernet" viewpoint.  The +/- 20 
PPM T1/T3 signals that become payload DS1/DS3 clients are "bit stuffed" 
rate adjusted to allow them to be inserted into a PRS synchronous client 
signal on a SONET/SDH ADM.  10G Ethernet WAN PHY does not do that.

Any equipment vendor or service provider that attempts to use the WAN PHY 
as a "client" signal will have dissatisfied customers.  It will give a bad 
perception of  the reliability of Ethernet over optical transmission 
services.  Changing the clock tolerance to +/- 20 PPM only created the 
perception of interoperability, not the reality.  That was the reason that 
I apposed it.

Thank you,
Roy Bynum

At 11:21 PM 1/17/2002 -0800, C. M. Heard wrote:
>On Thu, 17 Jan 2002, Roy Bynum wrote:
> > There is a single point of failure that prevents a WIS as defined
> > by IEEE from ever being an interface on SONET ADM.  The client
> > interface on a SONET ADM requires clock synchronization either
> > through "loop timing" or "PRS".  Neither of these are available in
> > the WIS.  This lack of synchronization to a transmission network
> > prevents the ADM from being able to multiplex the WIS signal into
> > a SONET signal.
>That conclusion is false.  It is is possible to multiplex the WIS
>SPE into a higher-order SONET signal because the WIS transmit clock
>is required to meet the SONET minimum clock frequency accurracy of
>+/- 20 ppm.  That is good enough to ensure that pointer justifications
>can absorb the timing differences between the WIS clock and the
>stratum clock used by a SONET ADM.  It is not necessary that the WIS
>be loop timed or synchronized to a stratum clock in order to do that.
>All this is spelled out in Section 2.4 of the T1X1.5 contribution.
> > As defined, the WIS can never be a client of a SONET or SDH system.
> > It can be a "peer" on an optical network only.  The T1X1.5 proposal
> > provides for a "peering" between a WIS and a SONET managed optical
> > network.  It does not provide for the WIS to be an interface on a
> > SONET system.
>I don't think that the authors of T1X1.5/2002-027 would necessarily
>agree, since that contribution explicitly states that "[ ... ] the
>ELTE function is intended to be realized within a SONET/SDH NE
>(potentially on a line card)."
>Mike Heard