Re: [EFM] Network timing?
I think that if we expect from EFM to deliver a rather wide range of different customer
services, transport of the network timing reference turns to be a significant feature.
For WEB browsing and FTP file transfers it is not necessary, of course.
Vladimir
Hugh Barrass wrote:
> Geoff,
>
> I agree wholeheartedly that any form of guaranteed latency or synchronous behavior
> is outside the scope of 802.3ah.
>
> However, if there are some PHY candidates that might allow such behavior and others
> which preclude it - the group may take that into account when weighing the options.
>
> The specification of any form of synchronous behavior may be left to vendors or it
> may be defined by another body as a standard to be applied over an 802.3ah Ethernet
> link.
>
> Hugh.
>
> Geoff Thompson wrote:
>
> > Matthew
> >
> > This is not possible within the Scope of the P802.3ah project
> > The project is for physical layers.
> >
> > There is no concept of guaranteed latency across the MAC or between ports
> > of a bridge (switch) in 802.3 and 802.1 Standards.
> >
> > Ethernet networks are not synchronous.
> >
> > That is not to say that some vendors may not provide some latency specs in
> > their products.
> >
> > Geoff
> >
> > At 04:04 PM 9/26/01 +1000, Beanland Matthew wrote:
> >
> > >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