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Re: [EFM] Network timing? [Etherloop?]

On 26 Sep 2001 16:04:00 +1000  "Beanland Matthew" wrote:
> I guess this is a question for the service providers out there. Imagining an
> EFM ONU supporting bearer emulation (say, in order to provide E1/T1 interfaces
> for connection to a legacy PABX), is there any interest in having the OLT
> propagate network timing (usually 8kHz, traceable back to some reference) to
> the ONUs by some method?

So do you envision this as a copper and fiber solution or a copper
only solution?  If this is fiber only, please ignore all the

If it is copper, using EFM to emulate the legacy PSTN via the legacy
PSTN seems unnecessarily complicated.

> Propagation of network timing is allowed for in the xDSL standards.

I am not sure if you are using this as an argument for or against
network timing.

Would propagating timing make more difficult some potential protocol
architectures for copper 10 mb/sec?  For example, the Elastic Networks
Etherloop seems to work quite well in terms of distance, speed and
tolerance of bad line conditions.  From what little I know of their
protocol, it doesn't use timing, but instead uses a master and slave
architecture.  I also understand this architecture is why Etherloop
out performs competing protocols.

I know that there is some skepticism about the Etherloop protocol and
Elastic Network implementation because it seems to perform better than
people thought possible.  I am not an expert in Etherloop; far from
it.  I have never used Etherloop at all.  However, at Copenhagen I was
going to present some results Frank Miller of Oregon Trails Internet
(OTI) put together of actual performance under a variety of
conditions.  OTI has been using Etherloop for a while and I believe
has it installed quite widely.  His slides show that Etherloop
actually performs better than specified out to at least 24k feet.

Due to a misunderstanding with Howard Frasier, Frank's slides got
deleted from the end of my presentation.   I will work with Howard to
get them restored so you can see them.

Due to scheduling conflicts, Frank Miller could not attend the
Copenhagen sessions for mid-September.  Perhaps he can make October
Los Angles sessions and give the results in person.  It is still up in
the air whether or not I will be able to make Los Angles as the
session times overlap with PoPtech 2001.


P.S. I would be very interested in hearing critiques of Etherloop, as we
are poised to make a big buy of Etherloop equipment.  Please feel free
to contact me privately.