fractional gigabit ethernet links?

Tue Jul 16 02:54:44 UTC 2002

Hello Alex,

I'd say this sounds obvious, but may be deceptively so...
If you are taking a pipe capable of 1000 mbit, and rate-limiting it to
311 mbit, the logic used may be:

In the last 1000 msec have there been more than 311mbits?  If yes: drop.

What you want is to shape the traffic, so the rule would be:
In the last 1000 msec have there been more than 311 mbits? If yes: store
until the msec period is up, then transmit.

If you are pushing 100 mbits over this link, it is entirely likely that
there will be a few sub-second burts up to 1000 mbit, and a few
sub-second drops to 0mbit.

An option for you would be to just figure out what the exact
rate-limiting rules are, and then shape it into those rules on your side
of the link -- assuming they wont change it to a shaping rule.

--Phil

-----Original Message-----
From: owner-nanog at merit.edu [mailto:owner-nanog at merit.edu] On Behalf Of
Alex Rubenstein
Sent: Monday, July 15, 2002 10:48 PM
To: nanog at merit.edu
Subject: fractional gigabit ethernet links?

Hello,

I'm trying to troubleshoot a problem with a fractional (311 mbit/second)
gigabit-ethernet line provided to me by a metro access provider.
Specifically, it is riding a gig-e port of a 15454.

The behavior we are seeing is an occasional loss of packets, adding up
to a few percent. When doing a cisco-type ping across the link, we were
seeing a consistent 3 to 4 percent loss.

For fun, the provider brought it up to 622 mbit/second, and loss dropped
considerably, but still hangs at about 1 to 2 percent.

There is no question in my mind the issue is with the line, as we've
done a wide variety of tests to rule out the local equipment (MSFC2s,
FYI).

Any clues would be exceptional.

-- Alex Rubenstein, AR97, K2AHR, alex at nac.net, latency, Al Reuben --
--    Net Access Corporation, 800-NET-ME-36, http://www.nac.net   --