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FYI - unproven technology

  • From: Curtis Villamizar
  • Date: Wed Oct 19 15:03:46 1994


For those that don't appreciate the consequences of using unproven
technology.  The good news on Mae-East is packet loss is down to 15%
from 40%?  :-(

Congratulations to Sprint for picking a technology that is known to
work for the Sprint NAP.  FDDI works.  We'll see how the others NAPs
do, though I'm not encouraged by test results so far.


BTW - this is Mae-East (the MFS bridged ethernet), not Mae-East+ (the
bridged FDDI).

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From: Sean Doran <[email protected]>
Reply-To: [email protected]
To: [email protected]
Subject: Moderately urgent: getting rid of annoying packet losses
Date: Wed, 19 Oct 1994 02:07:06 -0400
Sender: [email protected]

The Magnum boxes are *very* unhappy with inter-packet gaps of less
than about 23 microseconds, and drop back-to-back packets like
superheated rocks.

We have a kludge which will help until the MFS hardware gets fixed.

Those of you running one Cisco with EIP 10-0 microcode or better should
set the transmitter-delay of your MAE-EAST interface to 96 (0x60).
This will dramatically reduce the packet loss across MAE-EAST.

IMPORTANT: Those of you who have more than one box on your ethernet
drop to MFS will need to a/ acquire EIP 171-1 from Cisco and load
it in then b/ set the transmitter-delay of each of your MAE-EAST
interfaces to 0x360 (864).

The new microcode has apparently been well tested, and is doing the
right thing for and (drops
to most of you have fallen from 40% to much less than 15%).  It
works by assigning new meanings to the upper 8 bits of the transmitter-
delay value; this particular setting will delay the transfer of
the packet to the datalink controller when there is traffic
on the wire, then require an additional quiet time of 30usec, 
after which there will be the standard 9.6 usec IEEE 802.3 delay.

(The original intent apparently was to avoid drops when bursting
ethernet traffic encounters collisions by backing off on handing
the packet to the datalink layer; the application here is not quite
exactly what was intended, but definitely helps us).

Each of your routers attached to MAE-EAST must run the new EIP 171-6
microcode and have the 0x360 transmitter-delay setting.

Thanks to Robert M. Broberg of Cisco for the code.

Those of you without Ciscos will have to come up with a similar hack 


P.S.: We are *very* keen on PSI, NETCOM, and MCI to implement the
      change, especially PSI.  We aren't having problems with anyone
      else we exchange traffic with at MAE-EAST (other than Dante
      AS1133, but that's not a Cisco) but everyone would probably 
      benefit from the upgrade anyway.  Try pinging each of your peers
      in 192.41.177 a hundred or so times.

- - --
Sean Doran <[email protected]>  SprintLink/ICM engineering   +1 703 904 2089

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