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
> >
> >
>
>