RE: fractional gigabit ethernet links?

["Stephen J. Wilcox" <steve () opaltelecom co uk>]

I may be missing something but..

presumably their rate-limiting involves some form of queuing/buffering.. 

in which case assuming the ping is the only thing occuring, when the rate hits
the limit it will queue, delay and slow down the echo/reply 

and no packets should be lost?


on the other hand, if as is i think suggested below theres no buffer ie when it
hits the limit it starts dropping then i dont think thats a good way of rate
limiting as it only works for tcp and the network really needs to provide a way
to slow the ip layer down. i cant see how that will provide a usable service...

Steve

-- 
Stephen J. Wilcox
IP Services Manager, Opal Telecom
http://www.opaltelecom.co.uk/
Tel: 0161 222 2000
Fax: 0161 222 2008

On Mon, 15 Jul 2002, Phil Rosenthal wrote:

> 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 () merit edu [mailto:owner-nanog () merit edu] On Behalf Of
> Alex Rubenstein
> Sent: Monday, July 15, 2002 10:48 PM
> To: nanog () 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 () nac net, latency, Al Reuben --
> --    Net Access Corporation, 800-NET-ME-36, http://www.nac.net   --