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RE: Minimum IPG w/ WIS ?


Transmitted IPG out of the MAC is 96 bit times regardless of speed. This is
part of the MAC spec. A note in 4.4.2 indicates that the minimum IPG between
two non-collided packets at 1000 Mb/s is 64 bits. There is no indication of
the receive IPG for 100 Mb/s and even in the 1000 Mb/s case, the gap between
a collision fragment and a good packet is not covered. There are a number of
sources of IPG shrinkage and repeaters are only one of them.

I'm surprised receive IPG for 100 Mb/s isn't documented. I know calculations
were done during the development, but I've been unable to find a number in
the standard.


-----Original Message-----
From: rohit mitt [mailto:ro_mittal@xxxxxxxxx]
Sent: Wednesday, February 28, 2001 8:46 AM
To: THALER,PAT (A-Roseville,ex1); stds-802-3-hssg@xxxxxxxx
Subject: RE: Minimum IPG w/ WIS ?


I believe in 100/1000 Mb/s ethernet standards there
was a limitation that at the Receive end of an
ethernet link, there had to be a minimum of 8 bytes of
IFG. Do you recall if there was a minimum IFG at the
Transmit end. I believe the difference between the
Transmit and the Receive had to do with the fact that
you could have a repeater in between which might,
itself, add/drop idles to make up for clock tolerance.

In the 10gigE, we do not have repeaters but we still
might have a system to send ethernet over long
distances, say 160km. (Don't want to confuse the topic
but an example could be sending 10gigE over one
wavelength in an optical network). 

Looking at this application, do you think it makes
sense to specify a minimum number of IFGs at the
source itself


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