fractional gigabit ethernet links?

Tue Jul 16 09:03:49 UTC 2002

In other words..intermittent intergap delay?

At 01:33 AM 7/16/2002 -0400, Vincent J. Bono wrote:

>Since this is being done with the 15454s this is not true rate limiting,
>more its a matter of STS channels being made available for use on the Vlan
>assigned to the two GigE ports.
>
>We have experienced this problem when sending traffic in excess of 250mbps
>through either:
>
>a) 4 or more 15454 hops that tired to achieve timing off of eachother rather
>than a stratum one source:
>
><timing>===<15454>===<15454>===<15454>===<15454>===<15454>
>
>OR
>
>b) a 15454 that "uplinked" its OC48 backhaul through an active DWDM device
>(in our case a Sycamore SN8000)  when both the SN8000 and 15454 were again
>not on the same stratum one source :
>
><15454>===<sn8000>===<sn8000>===<15454>
>
>By not allowing a timing source to be more than 4 hops from any chassis and
>by ensuring that all DWDM devices in between are also timed the same, we
>have pushed up to 605mbps over a 15454 GigE link with no recorded packet
>loss.
>
>Hope this helps Alex,
>
>Vin
>
>PS
>
>As another aside we have seen problems when simultaneously using both ports
>on the 2 x GigE card for more then 200mbps a piece, but not with any
>regularity.
>
>-vb
>
>
>----- Original Message -----
>From: "Sush Bhattarai" <netnews at sush.org>
>To: "Alex Rubenstein" <alex at nac.net>
>Cc: <nanog at merit.edu>
>Sent: Monday, July 15, 2002 11:57 PM
>Subject: Re: fractional gigabit ethernet links?
>
>
> >
> > Might want to query your provider as to where the rate limitting is being
> > done. In some cases, if rate limit is being done egress from the layer 3
> > infracture towards the MAN layer 2 equipment, there might be a lack of
> > processing power on that device, causing the drops. Of course this will
> > depend on the type of device and whether the rate limiting is being done
>on
> > hardware or not too.
> >
> > Sush
> >
> > >
> > >
> > >
> > > 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   --
> > >
> > >
> >

Regards,

--
Martin Hannigan                    hannigan at fugawi.net