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  • Testing why a network is slow

    We've had a couple of users inquiring why the internet has been so slow as of late. Up until today I though the culprit was the world cup and people on our ISP streaming the games, but there are no games on today and I don't see any body using Youtube.

    This may be a stupid question, but how can I check if the slow network speeds are because of our network or because of our ISP? We've got about 60 users on our network at any given time and I've got no experience using packet analyzers.

    Can anybody offer some words of wisdom?

  • #2
    Re: Testing why a network is slow

    How do your users gain access to the Internet? Do you have a proxy server?

    Are any particular sites slow, or are we talking more generally?

    Do your switches log the traffic passing through them and provide statistics?
    Gareth Howells

    BSc (Hons), MBCS, MCP, MCDST, ICCE

    Any advice is given in good faith and without warranty.

    Please give reputation points if somebody has helped you.

    "For by now I could have stretched out my hand and struck you and your people with a plague that would have wiped you off the Earth." (Exodus 9:15) - I could kill you with my thumb.

    "Everything that lives and moves will be food for you." (Genesis 9:3) - For every animal you don't eat, I'm going to eat three.

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    • #3
      Re: Testing why a network is slow

      All users connect via a hardwire that sits behind a firewall, with no proxy server.

      The firewall we use keeps limited logs for a small period of time, which makes my life a bit harder when trying to troubleshoot.

      My main concern is always that a machine has been compromised and taking up a large portion of the networks bandwidth for malicious intention. I think this is highly unlikely, but like a true IT professional I'm paranoid

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      • #4
        Re: Testing why a network is slow

        use MRTG or something similar

        it will show you the levels of traffic across your router.
        needs a linux box with the Apache server installed, as well as perl and SNMP access.

        Your switches or routers may actually have some interogative tools, have you checked this at all ?
        Please do show your appreciation to those who assist you by leaving Rep Point https://www.petri.com/forums/core/im.../icon_beer.gif

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        • #5
          Re: Testing why a network is slow

          Make sure the patch Leads are not bent since this will slow the data speed down when it hits the corners.
          1 1 was a racehorse.
          2 2 was 1 2.
          1 1 1 1 race 1 day,
          2 2 1 1 2

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          • #6
            Re: Testing why a network is slow

            Hmmm I'm not paranoia :S
            Are there heavy downloads processing?
            What is you linespeed?
            Marcel
            Technical Consultant
            Netherlands
            http://www.phetios.com
            http://blog.nessus.nl

            MCITP(EA, SA), MCSA/E 2003:Security, CCNA, SNAF, DCUCI, CCSA/E/E+ (R60), VCP4/5, NCDA, NCIE - SAN, NCIE - BR, EMCPE
            "No matter how secure, there is always the human factor."

            "Enjoy life today, tomorrow may never come."
            "If you're going through hell, keep going. ~Winston Churchill"

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            • #7
              Re: Testing why a network is slow

              Linespeed is supposed to be 16.67 Mbps - I've spoken to our ISP and they claim that's the speed we're still getting.

              The firewall / switch doesn't seem to have a lot of data going through it (CPU Average is 19%) ...any idea's on how I can find where this bottleneck is? We haven't made any changes to our network infrastructure recently. I'm stumped

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              • #8
                Re: Testing why a network is slow

                ISP is always going to blame your users. So the easy way is to take your users out of the picture.

                Set up an outage, (I know this sucks with a large number of users). Connect single computer directly to ISP's equipment, removing all internal traffic. Do a number of speed test recording the results.

                This will tell you if you have an internal network issue or if you have a internet issue.

                Post results back, as we would like to know the results.

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                • #9
                  Re: Testing why a network is slow

                  Originally posted by kgantt View Post
                  ISP is always going to blame your users. So the easy way is to take your users out of the picture.

                  Set up an outage, (I know this sucks with a large number of users). Connect single computer directly to ISP's equipment, removing all internal traffic. Do a number of speed test recording the results.

                  This will tell you if you have an internal network issue or if you have a internet issue.

                  Post results back, as we would like to know the results.
                  I highly agree with you, but I believe it would just be easier to stay back on night, disable any service on the server that uses bandwidth, disable DNS and so forth so the server does not sure its connect and run tests on the server.

                  To check for internal network useage, there are millions of apps you can get to place on a firewall machine that will monitor network useage. Sadly, alot of these are really bad, and I can not recommend one (I have one that was made for me by a mate). When you get a good one, its easy as pie, install on Firewall server (or any inline server (or a PC that you put inline for this experiment)). IPCOP is a Unix Distro that I can recommend for this, but its rather old atm.

                  PS: Can we know what type of firewall and Routers your using?

                  Wofen
                  Good to be back....

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                  • #10
                    Re: Testing why a network is slow

                    Hope you have had some luck with this..

                    One thing I always make sure to do is verify that it is indeed the "Internet" they are reporting as slow and run my own speed tests from different machines to verify that.

                    Some (if not most) users associate a delay or problem with an application or other local running process with the Internet. Ask for examples and see if you can narrow the problem down to either a specific website, application or even time of day.

                    Always run your own speed tests. I favor Speakeasy (http://www.speakeasy.net/speedtest/) but you may find another one you like to use. I've found that ISPs will say anything to get you off the phone and close your case unless you have proof that they are not meeting the CIR you agreed to (if you have one). Some ISPs will also shape traffic without informing you and have you chasing your tail for days trying to figure out what is wrong.

                    Maybe I have just had some bad experiences...

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                    • #11
                      Re: Testing why a network is slow

                      No kidding. If anyone out there is unaware of just how many problems the average user will describe as "the Internet", just watch episode 1 at http://www.thewebsiteisdown.com/
                      Gareth Howells

                      BSc (Hons), MBCS, MCP, MCDST, ICCE

                      Any advice is given in good faith and without warranty.

                      Please give reputation points if somebody has helped you.

                      "For by now I could have stretched out my hand and struck you and your people with a plague that would have wiped you off the Earth." (Exodus 9:15) - I could kill you with my thumb.

                      "Everything that lives and moves will be food for you." (Genesis 9:3) - For every animal you don't eat, I'm going to eat three.

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                      • #12
                        Re: Testing why a network is slow

                        Have you tried ''Speedtest' and verify if the ISP is telling the truth . Need to isolate and find where the problem lies before we can make a fix


                        Bryan

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                        • #13
                          Re: Testing why a network is slow

                          Not sure what routers/firewall you are using but if its a cisco, check the statistics on the interface. Look for any potential bottlenecks. (coming in a 100mb int and leaving via a 10mb int) Look for drops and check the queues for congestion.Also just because an interface is a fast ethernet interface dont assume that you will get 100mb throughput through that interface. By default on cisco equipment, you can only use up to 75 percent of the bandwidth on that interface.
                          CCNA, CCNA-Security, CCNP
                          CCIE Security (In Progress)

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                          • #14
                            Re: Testing why a network is slow

                            Originally posted by tehcamel View Post
                            use MRTG or something similar

                            it will show you the levels of traffic across your router.
                            needs a linux box with the Apache server installed, as well as perl and SNMP access.
                            Something like this is your best bet, running local speedtests from a website isn't all that helpful as you don't know what other traffic is occurring at that time on your network.

                            I've setup MRTG in the past to monitor links between sites, it will graph things nicely and give you an easy way to spot bottlenecks.

                            If you want to dig a bit deeper (for an example if it's constantly maxed out) you could mirror the port of your gateway and run wireshark etc on a laptop/machine connected to the mirror.

                            What firewall/router are you using?

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