RE: Chapter 46: preamble length
Brad,
I am not aware of any place in 802.3ae where we allow the preamble to be
altered. Clock compensation is done only by deleting and inserting idles, or
when continuous sequence ordered sets are being received by deleting
sequence ordered sets.
The WIS is not a good example for clock compensation. It gets a scrambled
data stream and the only way it could add or delete from it without
clobbering data would be to implement most of the PCS receiver to
synchronize to the 64B/66B frames and unscramble then implement the PCS
transmitter to get back to a scrambled 16-bit wide data stream to put in the
Sonet frames.
A WIS is normally coupled to its PCS so that the PCS can do any necessary
clock compensation.
Regards,
Pat
-----Original Message-----
From: Booth, Bradley [mailto:bradley.booth@xxxxxxxxx]
Sent: Wednesday, March 28, 2001 12:04 PM
To: stds-802-3-hssg@xxxxxxxx
Subject: RE: Chapter 46: preamble length
There are a number of places within 802.3ae that synchronization between
clock domains may require some form of compensation. The WIS was just an
example of a part of the structure that may require clock compensation.
Generally, we permit shortening of the IPG and preamble to assist with this
compensation so that the data remains untouched.
I'm not sure if that's helping you understand it any better.
Cheers,
Brad
-----Original Message-----
From: Sanjeev Mahalawat [mailto:sanjeev@xxxxxxxxx]
Sent: Wednesday, March 28, 2001 1:46 PM
To: Booth, Bradley; stds-802-3-hssg@xxxxxxxx
Subject: RE: Chapter 46: preamble length
Booth,
At 10:08 AM 03/28/2001 -0800, Booth, Bradley wrote:
>In 10GbE, truncation of the preamble can occur due to
>the asynchronous timing associated with the WAN PHY.
PCS + PMA = LAN PHY
PCS + WIS + PMA = WAN PHY
The PCS and PMA processes are common in both LAN and WAN
Phy.
The only difference is extra WIS. And all WIS is supposed to
do is
take the MAC frame (Preamble + Data + IPG) and encapsulate
it
in STS-192c frame without any involvement, visibility into
the MAC framing
process. So, I am not getting where and why the WIS should
open the MAC
frames and try to change it. Could you please explain it a
bit more?
Thanks,
Sanjeev
>
>Cheers,
>Brad
>