From: Wade Edwards (wade.edwards@xxxxxxxxxxxxxxxxxxx)
Date: Fri Aug 23 2002 - 14:38:01 GMT-3
But with that logic, modems (specifically the connection from DTE to
DCE) use synchronous communication because the start and stop bits
synchronize each character of data. The receiver sees the start bit and
synchronizes to the transmitter clock. The clocking is transferred in
the encoded data.
I just don't think of it that way.
By the nature of Ethernet, as you start adding more and more devices to
that medium total throughput goes down because each device is trying to
access the medium in an asynchronous manner. If there is never any data
to transmit on an Ethernet network (with keepalives turned off) there is
no clock.
On an ATM network, if there is never any data to transmit there is still
clocking and order.
To me this mean asynchronous for Ethernet and synchronous for ATM.
L8r
-----Original Message-----
From: Asim Khan [mailto:asimmegawatt@yahoo.com]
Sent: Friday, August 23, 2002 2:43 AM
To: Przemyslaw Karwasiecki; Michael Snyder
Cc: 'Michael Spencer'; ccielab@groupstudy.com
Subject: RE: ethernet
I think ethernet is synchronous. The reason is in any
synchronous transmission, the receiver uses a clock
which is synchronized to the transmitter clock. The
clock may be transferred by either:
1)A seperate interface circuite.
2)Encoded in the data (like Manchester encoding,AMI
encoding).
Now in ethernet an encoded clock is used.
Regards.
Asim Khan
--- Przemyslaw Karwasiecki <karwas@bellsouth.net>
wrote:
> Ethernet is using something called Manchester
> encoding.
> It basically means, that in order to provide clock
> synchronization
> between frame transmitter and receiver, each zero is
> represented
> by sequence of 01 and each one is represented by 10.
> By doing so, it makes it possible to maintain clock
> synchronization
> even in case frame contains long sequence of zeroes
> or ones.
> And, yes, before each frame, there is a short
> sequence send
> called preamble (but I believe this is layer 1 not
> 2),
> which makes it possible to delineate beginning of
> the frame.
>
> Is it synchronous -- IMHO yes, but it depends on
> definition
> of the term synchronous.
>
> Przemek
>
>
> On Thu, 2002-08-22 at 17:17, Michael Snyder wrote:
> > Where's the clock?
> >
> > Believe every Ethernet transmission starts with a
> series of one's and
> > zero's sent before the packet header.
> >
> > This layer two header provides the clock. So it
> it's async before the
> > packet is transmited, and synced as the packet is
> transmited.
> >
> > Does this help?
> >
> > I have a better question for you, is ATM sync or
> async. Really? You
> > don't think there's a sync'ed clock signal on the
> fiber cables. About
> > as clear as mud huh?
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com
> [mailto:nobody@groupstudy.com] On Behalf Of
> > Michael Spencer
> > Sent: Thursday, August 22, 2002 1:04 PM
> > To: ccielab@groupstudy.com
> > Subject: ethernet
> >
> > Is ethernet synchronous or asynchronous?
> >
> >
> > ---------------------------------
> > Do You Yahoo!?
> > HotJobs, a Yahoo! service - Search Thousands of
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>
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