From owner-freebsd-net@FreeBSD.ORG  Wed Apr 12 15:13:42 2006
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Date: Wed, 12 Apr 2006 16:13:33 +0100
From: Brian Candler <B.Candler@pobox.com>
To: fooler <fooler@skyinet.net>
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Cc: freebsd-net@freebsd.org, Julian Elischer <julian@elischer.org>,
	"M. Parsons" <mrparsons@gmail.com>
Subject: Re: PPPoE question.
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On Wed, Apr 12, 2006 at 10:59:52PM +0800, fooler wrote:
> >>set speed sync
> >
> >And how does that change the pppoe ethernet frames?
> 
> nothing change and still the same... ethernet frames are at layer 2 while 
> synchronization (either asynchronous or synchronous) is at layer 1... 
> synchronous is much better than asynchronous for ethernet links...

Then I think you have a misunderstanding. Ethernet frames are *always*
synchronous. There are no 'start' and 'stop' bits in ethernet, only frame
delimiters.

The sync/async difference only has meaning for serial links (e.g. where
layer 1 is RS232 / V24)

PPP frames carried inside ethernet (i.e. pppoe) are therefore also carried
using synchronous encoding, since ethernet is synchronous.

Brian.