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Re(2): [EFM] Network timing? [Etherloop?]

Hi Fletcher,

I was thinking principally fiber, although I am aware of VDSL systems which
perform E1/TI transport. By the reference to the PABX I'm thinking business
rather than residential.

In my experience access network operators offer both E1/T1 private line and
Ethernet based data services to the same (business) customer site, and wish to
do this in the cheapest way possible (over the same infrastructure). Typically
this has meant SONET/SDH and/or ATM transport.

If EFM cannot emulate E1/T1 private line transport (by whatever method) then I
think it will suffer in this marketplace because access network operators
wishing to continue to offer this service (and being unable/unwilling to
convince/force their customers to move to VOIP for PSTN access) will need to
have parallel infrastructure to support E1/T1 private lines. This is not to say
that EFM will not succeed in its niche.

I'm sorry but I do not have experience with Etherloop, and I don't see the
connection between rate/reach and network timing to support emulated E1/T1
private lines.

Best Regards,


Fletcher E Kittredge  (26/09/01  22:13):
>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
>> 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.