Ethernet LAN Dropped packets/broken TCP connections

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Subject Author Date
Dropped packets/broken TCP connections amattina 08-23-06
Posted by on August 23, 2006, 9:48 am
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I'm posting this in this group because I believe that this problem
could have something to do with TCP connections not working properly
via our provider. If you have any ideas I would greatly appreciate it.
--
SETUP
Cisco 2811 ISR on 4mbit metro ethernet.
~200 users

Problem
Web pages are coming up either
a) perfectly
b) half mangled with some images and screwed up tables or
c) not at all

There is no pattern as to when or why a page might not come up. Most of
this happens at lunchtime while people sit at their desks and browse.
More usage = more of this problem. Tried cranking up the bandwidth to
10mbit and still had the same problem.

Example:
This is what a webpage might look like:
http://129.21.125.13/~adam/gg/screenshot_corresponding_w_capture.JPG

This is what the capture looks like:
http://129.21.125.13/~adam/gg/msn_ss_part1.JPG
http://129.21.125.13/~adam/gg/msn_ss_part2.JPG

I realize that retransmissions are normal, and this is what a normal
loss/retransmit should look like(taken from my home and office
connection:
http://129.21.125.13/~adam/gg/good_packet_loss.JPG

Notice the 'Continuation packets' in the good packet loss image. I
don't get those on the problem network.

I've troubleshot this down to the ISR and provider uplink. The
provider from their NOC said that everythign on the line looked good
and we don't have a ton of dropped packets on the ISR which one might
expect. Any ideas? I've been working on this for weeks.

Thanks,
Adam


Posted by Hansang Bae on August 24, 2006, 10:37 pm
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amattina@gmail.com wrote:

> I'm posting this in this group because I believe that this problem
> could have something to do with TCP connections not working properly
> via our provider. If you have any ideas I would greatly appreciate it.

You are getting resets from the web server. That certainly is not
normal. My first gut feel is that your NAT tables on the routers are
getting screwed up. Have you looked for NAT bugs on CCO?

--

hsb


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