Re(2): [EFM] Network timing?
Hi Frank,
Sorry if I am going over old ground. I've been reading EFM since May and I must
have missed the discussion.
Yes, I was thinking of something like ATM CES. In ATM CES the deviation of the
bearer frequency at the source against the network timing may be encoded using
SRTS allowing the bearer's timing information to be recovered at the
destination (only if the same network timing is present there).
I am not proposing a method, just seeing if there is interest in the service
provider community for the application. They should comment on rates, etc.
I would think that this service could be supported using MAC frames. There are
issues with latency, etc, but I am not trying to change the fundamental nature
of Ethernet. And I certainly don't want to take the lid of the whole DBA thing
:-)
Matt
Frank Coluccio (26/09/01 18:10):
>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
>>
>>
>
>