RE: Operational issue: Packet loss at Pacbell NAP

Hi Dave and Kent,

> High bandwidth-delay product paths on a heavily loaded OC-3 to OC-3
> circuit will strain the ATM switch buffers. If you can detect
> recurring losses on a high BDP path across an all-OC3 virtual
circuit, then
> look for buffer exhaustion on the OC3 interfaces. If no one at Pac
> knows what to do, tell them to look in the files in Fred Chang's
> Engineering Group for Kent England's ATM NAP switch test plan and go
out and
> get some test gear that will stress an OC3 link in the lab. Mike
Rudik in
> the lab knows what to do to test for this. But my recollection was
that the
> BPX had enough buffers to run UBR over a full OC3.

Nope. The problem is link congestion between SJC and SFO. Pacbell
was apparently not monitoring this. By rerouting some traffic, they
were able to shift the peers that it affected. It, with 100%
is within the cloud that makes up the PB NAP.

We've identified the facts that occured in this particular situation.
The problem was definitely **not** due to link congestion as we have
stats on the utilization of the OC3s. The rerouting which occured as a
result of this problem has been corrected.

We continue to monitor our OC3 links for any further problems. If you
identify any additional issues, please feel free to submit a trouble
ticket with our Network Data Center at 1-800-870-9007.


Steve Ellis
Pacific Bell/SBC
NAP Product Manager
(925) 823-2722 (Phone)

Um, Steve? Can you share what the problem, after all the facts were
identified, was? And does the routing changes that were made having been
corrected imply the state of >10% packetloss will be recurring now?