Network Troubleshooting

I run into the problem of a database admin for a Web based system telling me that people in (pick a building) are having issues with the app being slow, and since he can access the application from our building (Where the server resides for this app) very fast, he wonders if it may be a bandwidth issue. I have very limited tools at my disposal such as PRTG and Whats Up Pro. I don't see any bandwidth issues, and point that out. I am not real hip on passing the buck, and would prefer to be able to know conclusively is it something todo with latency, bandwidth or something else network related.

I am looking at something like the ethereal school, but don't want to waste money on learning the wrong skill, and still not know how to determine the cause of a problem like this, when one exists.

I would appreciate any and all commends to recommend a topic to study, learn, course, software, school etc that would be the correct discipline to learn how to troubleshoot this scenario.

Bruce D. Meyer, CCNA, MCSE Network Analyst City of Columbia

measure it from both places - prefeably on the same PC (ie a laptop is easiest).

then use that as a baseline to see if there is a problem worth investigating.

any sort of sniffer is great for analysing what a particular problem is - once you can pick out the traffic involved.

if you want to learn this stuff, then i really like the Laura Chappell ebooks.

the hardest thing to apply to IT problems (ie - before you even figure out they are network problems) is common sense :)

I just visited Laura Chappell's web site. Very nice stuff. I appreciate the help.

stephen wrote:

what's the topology?

I've been there before, as have probably half the people here. I've tried explaining results of a sniffer trace and have seen the old "deer in the headlights" stare. Once the server or application admin gets past what they understand easily, all they hear is that it is something with the network.

I have found the best thing to do after I get the network out of the picture as the problem is to run iPerf. Put the server part on a windows machine near the server, or on the server if it is Windows. Run the client from a laptop near where things are slow. If you get about 75 Mbps between the server and the clent parts, tell them that there is a lot of free bandwidth.

In my exerience saying, "I've looked at the sniffer traces and the delays in the responses to queries are much longer than the time needed to see an acknowledgement packet, therefore it seems likely to be an application problem" gets you nowhere. Saying, "Look, there's 75 Megs of bandwidth to your server from here" will get an acknowledgement that it might not be the network and a thank you for checking it out.

You have to make sure that you've checked things out though. If you know it's not a bandwidth issue it is a helpful tool and gives people something they can understand. If you haven't ruled it out, it is just a bluff. You'll be found out if you use it too often.