How to troubleshoot wide area network performance problem?

Alex Hewitt hewitt_tech at comcast.net
Thu Jul 10 19:36:46 EDT 2008


I have clients with an interesting network problem. One location in
Bedford New Hampshire using a fractionated T1 has routinely been
transmitting studies to an office in Nashua New Hampshire. There have
been no problems with this for at least 18 months. However recently
(about a week ago), the transmissions suddenly became slow, really slow.
A transmission that was taking around 10 minutes suddenly jumped to 2-3
hours. The customer in Bedford New Hampshire is using One
Communications. So far I haven't asked them to look at this problem
because I've been trying to clarify it. The office in Nashua has
Comcast business class service with a static IP address. 

Here's where it gets interesting. I had the Bedford client transmit the
data to my system in Manchester New Hampshire. I have Comcast
residential service. The data usually takes about 8 minutes to arrive at
my location. I then send the data to the Nashua office and it typically
takes 25-30 minutes. The payload is a collection of images that are
typically between 65 and 70 MB. 

Today Comcast at the request of the customer sent someone on site to the
Nashua site. The tech did some speed tests using the DSLReports
Speakeasy test suite. He was getting  20 mbs down, 3+ mbs up which is
pretty decent. For the fun of it I had him download a 47 MB antivirus
program. His first try was ridiculous telling him it was going to take 4
+ hours. I had him break the connection and try again and this time the
download took around a minute. 

And it gets more interesting...another client in Salem New Hampshire
needed to send their data to the Nashua site (they use Verizon DSL). It
arrived in about 8 minutes.

So my Comcast connection which is fairly decent is taking a half hour to
send 65-70 MB to the Nashua site. The Salem site is taking 8 minutes for
something approximately the same size and the Bedford site is taking
several hours.

Traceroute doesn't show much interesting - it craps out after the first
5 hops. Pinging (standard payload) from my office to the Nashua site is
averaging less than 20 ms. One odd thing is that when I'm in the process
of sending data to the Nashua site my pings jump up to 650 - 800 ms. 

The Comcast tech was happy to conclude that the Nashua site was working
properly. They checked transmission levels, noise and of course the guy
downloaded some files and ran the Speakeasy speed tests and all of that
looked good.

Any ideas how to proceed on a problem like this? Currently I'm having
the customer transmit their data to me and then I re-transmit because my
connection although slow is probably 4 or 5 times faster than theirs.

-Alex






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