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Re: [802.3af] clocking over ethernet


Your application may be best served by using the Network Time Protocol

It is fairly inexpensive to implement a small NTP client in Ethernet
devices, and getting cheaper.

You may wish to look at this comprehensive URL:

and also read the archives at the Usenet newsgroup:



Steve Jackson

* * *

WM wrote:
> Hello together,
> sorry for dissturbing. I know that this is maybe not the right place to ask
> for it but maybe here are the right people to give me a helpful answer.
> In principle it could be also a nice add on for 802.3af.
> Power over MDI is what we are looking for for several years and it is a
> must for several applications like VoIP phones etc. but to fully utilize
> and replace ATM, ISDN or other media by ethernet I think at least for
> migration a way to synchronize devices would be usefull. An independent
> clock source like GPS is not usefull in our application.
> Is there any way to clock or at least sync devices on the ethernet? One way
> would be to use e.g. the link pulses but switches donīt guarantee that all
> ports are in sync.
> The power supply in power over MDI would also be a way to add a sync pulse.
> Many thanks in advance for your comments.
> Best regards
> Joerg
> --------------------------------------------------
> Wilhelm Mikroelektronik GmbH
>    Sueggelstr. 31  -  44532 Luenen  -  Germany
>   phone ++49 2306 928280  fax: ++49 2306 928289
> --------------------------------------------------