Thread Links Date Links
Thread Prev Thread Next Thread Index Date Prev Date Next Date Index

Re: A Question about "Inter Packet Gap and SOP Lane alignment"


A subversive maneuver? Me? Subversive? Peeshaw!

I just don't feel compelled to accept an increasingly complicated
IDLE signal in order to accomodate LSS, and I can't accept the 
argument that using SOP+Data for the deskew marker is not sufficiently
robust because of the potential presence of LSS words.  To me, this
is merely one more way in which LSS complicates our life, and one more
reason for me to reject LSS.

As to skew, I don't see why the IDLE to SOP+Data (/S/D/D/D/) scheme can't
accomodate arbitrarily large skew.  As you say, we are already using
a counter to space the /A/ symbols (at the transmitter). So, we
could use a counter to screen the IDLE to /S/D/D/D transitions at the
receiver.  We could perform the deskew ONLY in the cases where the
spacing between the transitions is sufficiently large to accomodate
whatever skew goal we set for ourselves.

I brought up the alternative deskewing technique because it appears that
we are grappling with the problem of trying to accomplish way too much
during IDLE, and we are faced with the classic "wrapping jello in 
rubber bands" problem.  Even leaving LSS out of the picture (which I
sincerely hope we do) there is still too much going on during IDLE.

Consider that the InterPacket Gap was originally intended to allow
the signal to decay on coax cables, and (more importantly) to give
receivers time to do their end of packet house keeping. IDLE and
the InterPacket Gap were never supposed to be an opportunity to
convey data.

Unfortunately, nature (and any given standards committee) abhors a 
vacuum.  So some people look at the IPG (and the preamble too) as
an opportunity to "add value" to Ethernet.  As if Ethernet needed
any further enhancement to its value proposition!  One of the problems
I have with LSS is that it commandeers the IPG for 10 Gig, burdening
us with a new protocol that we will have to carry forward into future
generations for the sake of backwards compatibility.  We should keep
in mind that three previous generations of Ethernet have managed to
achieve a respectable level of success in the market without
packing information into the "wasted space" of the IPG and Preamble.

As to your assertions about the product demonstrations from "you know
who", I hope that you understand that I am not engaging in "subversive
maneuvers" to protect the narrow interests of any particular party.
Rather, I am engaging in subversive maneuvers for the sheer joy of it.

As to FUD, I will readily admit that LSS scares the peeshaw out of me.

Howard Frazier
You Know Who, Inc.