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

From: Roy Bynum <[email-masked]>
Date: Thu, 17 Jan 2002 10:50:56 -0600

Mike,

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.
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.

Thank you,
Roy Bynum
Orbital View LLC

At 10:27 AM 1/16/2002 -0800, C. M. Heard wrote:

>Colleagues,
>
>FYI: the following contribution to T1X1.5 (written by Tom
>Alexander, David Martin, and Steve Gorshe) may be of interest,
>as it presents a detailed argument that ELTE can be
>realized within existing NEs -- e.g. as a 10GBASE-W line
>card -- and does not require a separate external piece of
>equipment.  That was exactly the message of the last slide
>in the WIS MIB design team's IETF52 presentation (see
>http://norseth.org/ietf/hubmib/ietf52wisMibPresentation.PDF)
>illustrating a 10GBASE-W interface on a SONET ADM.
>
>Regards,
>
>Mike Heard
>
>CONTRIBUTION#: T1X1.5/2002-027 (2X150270)
>LINK: http://www.t1.org/FileMgr/GetOneFile.taf?FileName=2X150270&NW=Y
>TITLE: Clarification of the 10GBASE-W Ethernet Line Terminating
>Equipment (ELTE) function and its realization within existing SONET
>equipment
>DESC: This contribution clarifies the issues that have been raised with
>regards to the proposed ELTE function, needed to adapt a 10GBASE-W
>Ethernet WAN-PHY signal to a SONET/SDH STS-192c/VC-4-64c signal. In
>particular, we demonstrate that such adaptation does not need
>additional NEs; that is, the ELTE function can be realized by existing
>NEs, and does not require new equipment to be added to a SONET/SDH
>network.
>CONTACT(S): Steve Gorshe ([email-masked] (503) 431-7440)
>SOURCE: Nortel Networks, PMC-Sierra

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From: "C. M. Heard" <[email-masked]>
Date: Thu, 17 Jan 2002 23:21:02 -0800 (PST)

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)."

Regards,

Mike Heard

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From: "C. M. Heard" <[email-masked]>
Date: Thu, 17 Jan 2002 23:21:02 -0800 (PST)

Regards,

Mike Heard

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From: Roy Bynum <[email-masked]>
Date: Sat, 19 Jan 2002 21:32:23 -0600

Mike,

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

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From: Roy Bynum <[email-masked]>
Date: Sat, 19 Jan 2002 21:32:23 -0600

Mike,

Thank you,
Roy Bynum