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.


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:



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 :


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

Hope this helps Alex,



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



Are you thinking of rate-limiting or traffic shaping ?
I'd expect rate-limiting of bursty traffic to lose some packets
irrespective of the L3 hardware/CPU capacity

In other words..intermittent intergap delay?

one small note, in passing:

In other words..intermittent intergap delay?

when PAIX sells what it calls Fractional Gig E, it's just Gig E with
rate limiting. nothing special at the link level.