From: Jason Sinclair (sinclairj@xxxxxxxxxxxxxxx)
Date: Thu Aug 22 2002 - 21:36:51 GMT-3
Michael,
You are correct, ATM does not have a preamble. The very meaning of ATM
(Asynchronous Transfer Mode) lends itself to the idea that it is indeed
asynchronous and from the ATM Forum:
"Asynchronous Transfer Mode: A transfer mode in which the information is
organized into cells. It is asynchronous in the sense that the recurrence of
cells containing information from an individual user is not necessarily
periodic."
Now remember the ATM physical medium sublayer? This is basically responsible
for timing information between sender and receiver. Hence, it is this layer
that provides the synchronization in ATM networks.
Hence ATM is considered asynchronous.
Regards,
Jason Sinclair CCIE #9100
Manager, Network Control Centre
POWERTEL
55 Clarence Street,
SYDNEY NSW 2000
AUSTRALIA
office: + 61 2 8264 3820
mobile: + 61 416 105 858
email: sinclairj@powertel.com.au
-----Original Message-----
From: Michael Snyder [mailto:msnyder@ldd.net]
Sent: Friday, 23 August 2002 10:21
To: 'Jason Sinclair'
Subject: RE: ethernet
And ATM? I don't remember cell's having preambles.
-----Original Message-----
From: Jason Sinclair [mailto:sinclairj@powertel.com.au]
Sent: Thursday, August 22, 2002 7:15 PM
To: 'Wade Edwards'; Michael Snyder; Michael Spencer
Cc: ccielab@groupstudy.com
Subject: RE: ethernet
All,
To clarify this let's define sync versus async:
Sync:
Data is transmitted at a steady consistent rate via the use of a
clocking
mechanism.
Async:
Data can be sent at irregular intervals as there is no clocking sync
between
devices and another method will be used to provide the synchronisation.
This
is usually via start and stop bits.
Ethernet:
There is no clocking between nodes and sync is provided via the preamble
of
the Ethernet frame. This is a series of alternating ones and zeros that
denotes the start of the frame. This is used by the receiving node to
sync
with the transmitter. Hence Ethernet is defined as asynchronous.
Regards,
Jason Sinclair CCIE #9100
Manager, Network Control Centre
POWERTEL
55 Clarence Street,
SYDNEY NSW 2000
AUSTRALIA
office: + 61 2 8264 3820
mobile: + 61 416 105 858
email: sinclairj@powertel.com.au
-----Original Message-----
From: Wade Edwards [mailto:wade.edwards@powerupnetworks.com]
Sent: Friday, 23 August 2002 08:20
To: Michael Snyder; Michael Spencer
Cc: ccielab@groupstudy.com
Subject: RE: ethernet
I would submit that Ethernet is asynchronous because it is an ad hoc
medium and synchronization occurs in-band and is per packet. ATM is
synchronous because there are certain timeslots and synchronization
occurs out of band.
L8r
-----Original Message-----
From: Michael Snyder [mailto:msnyder@ldd.net]
Sent: Thursday, August 22, 2002 4:18 PM
To: 'Michael Spencer'
Cc: ccielab@groupstudy.com
Subject: RE: ethernet
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?
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