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RE: [EFM] Network timing?




Roughly speaking it takes 3.5Mbit/s of Ethernet frames to carry a T1/E1, and about 70Mbit/s to carry a T3.

Clock recovery from a non-deterministic packet stream is quite a challenge by doable, even to Startum 1. However, it's a lot easier to carry circuits in a side-band :-).

Bob Barrett 

> -----Original Message-----
> From: owner-stds-802-3-efm@majordomo.ieee.org
> [mailto:owner-stds-802-3-efm@majordomo.ieee.org]On Behalf Of Frank
> Coluccio
> Sent: 26 September 2001 09:10
> To: Matthew.Beanland@xxxxxxxxxxxxxx
> Cc: stds-802-3-efm@ieee.org
> Subject: Re: [EFM] Network timing?
> 
> 
> 
> Hi Mathhew,
> 
> It sounds like you're desribing a variant of FDDI II's  "guaranteed" T1 
> capabilities, or some form of T1 emulation _a_la_ ATM. I've 
> discussed this 
> possibility with others here in the past. At what "super rate" 
> (minimum entry 
> level) of Ethernet would you propose, first, before such an 
> isochronous approach 
> should be considered? [Or, should it be considered at all?] 
> 
> In 10 Mb/s or lower, I don't think so. At 100 Mb/s or higher, a 
> possibility, imo. 
> What say?
> 
> Frank 
> 
> > 
> > Hi EFMers,
> > 
> > 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?
> > 
> > Propagation of network timing is allowed for in the xDSL standards.
> > 
> > Should we require propagation of network timing in EFM it could 
> be propagated
> > by either the Ethernet symbol rate itself or via some coding 
> method. Some
> > physical layer schemes (ATM25 comes to mind) use a low spec 
> oscillator for the
> > line rate and insert special line tokens at 8kHz to allow user 
> side equipment
> > to recover network timing if required. It would be possible to 
> use one of the
> > non-data 8B/10B tokens as a timing marker and send at 8kHz, 
> alternatively if
> > there is an OAM block it could be sent at 8kHz rate.
> > 
> > Best Regards,
> > 
> > Matt
> > 
> > Matt Beanland, Project Manager/Principal Architect
> > Telecommunications Research and Development, Fujitsu Australia Ltd
> > 5 Lakeside Drive, Burwood East 3151, Victoria, Australia
> > e-mail: matthew.beanland@xxxxxxxxxxxxxx         Phone: (613) 9845 4313
> > 
> > 
> 
>