The last time Hackerfall tried to access this page, it returned a not found error. A cached version of the page is below, or clickhereto continue anyway

Troubleshooting the Internet | Mozilla IT

Introduction

If you’re working from home, a coffee shop or even an office and are experiencing “issues with the Internet” this blogpost might be useful to you. We’re going to go through some basic troubleshooting and tips to help solve your problem. At worse gather data so your support team can investigate.

Something to keep in mind while reading is that everything is packets. When downloading a webpage, image, email or video-conferencing, you have to imagine your computer splitting everything into tiny numbered packets and sending them to their destination through pipes, where they will be reassembled in order. Network issues are those little packets not getting properly from A to Z, because of pipes full, bugs, overloaded computers, external perturbations and a LOT more possible reasons.

Easy tests

We can start by running some easy online tests, even if not 100% accurate, you can run them in a few clicks from your browser (or even phone) and can point toward the right direction.

Speedtest is a good example. Hit the big button and wait, don’t run any download or bandwidth heavy applications. The best is to know what a “normal” value is, so you can compare both.

As some sneaky providers can prioritize connections to the famous Speedtest, you can try another less known website like ping.online.net. Start the download of a large file and check how fast it goes.

Note that the connection is shared between all the connected users. So one can easily monopolize the bandwidth and clog the pipe for everyone else. This is less likely to happen in our offices where we try to have pipes large enough for everyone, but can happen in public places. In this case there is nothing much you can do.

Next is a GREAT one: Netalyzr. You will need Java but it’s worth it (first time I have ever said that). There is also an Android app but it’s better to run it from the device experiencing the issue (but it’s also interesting to see how good your mobile/data “Internet” really is). Netalyzr will runs TONS of tests, DNS, blocked ports, latency, etc… And give you a report quite easy to understand or share with a helpdesk. See Mozilla’s Paris office.

Some ISPs start to roll out a new version of the Internet, called IPv6 (finally!). As it’s “new” for them, there can be some issues. To check that, run the test on Test-ipv6.

Basic connectivity

If the previous tests show that something is wrong or you still have a doubt, these tools are made to test basic connectivity to the Internet as well as checking the path and basic health of each network segments from you to a distant server.

“ping” will send probes each second to a target and will reports how much time it takes (round trip) to reach it. For an indication, a basic time between Europe and the US west coast is about ~160ms, US east to US west coast ~90ms, Taipei to Europe ~300ms. If it is higher than that you might indeed see some “laggish/slow Internet”.

“traceroute” is a bit different; it does the same but shows you the intermediate hops in between source and destination.

The best in this domain is called “mtr” and is a great combination of the previous 2: for each hop, it runs a continuous ping. Add –report so you can easily copy and paste the result if you need to share it. Having some higher latency or packet loss for a hop or two is usually not an issue. This is because network devices are not made to reply to those tests, they just do it if they are not too busy with their main function, redirecting a packet in a direction or another. A good issue indicator is if many nodes (and especially your target) start showing packet loss or higher latency.

If the numbers are high on the first hop this means something is wrong between your computer and your home/office/bar’s Internet gateway.

If the issues appear “around the middle” it’s an issue with your ISP or your ISP’s ISP and the only thing you can do is to call their support to complain or change ISP when possible. That is what happened with Netflix in the US.

If the numbers are high near the really end it’s probably an issue with the service you’re testing, try to contact them.

Wireless

An easy one when possible. If you are on wireless try to switch to a wired network and re run the tests mentioned above. It might be surprising but wireless isn’t magic

Most of the home and small shops wifi routers (labeled “BGN” or 2.4Ghz) can only use 1 out of 3 frequencies/channels to talk to their clients, and clients have to wait for their turn to talk. So imagine your neighbor’s wifi is on the same frequency. Even if your wifi distinguishes your packets from your neighbor’s, they will have to share the channel. If you have more than 2 neighbors (Wireless networks visible in the wifi list), you will have an non optimal wireless experience and this is exponential.

To solve/mitigate it you can use an app like “Wifi Analyzer” on Android. X are the frequencies, only 1, 6 and 11 are really usable as they don’t overlap. and Y is how noisy they are. Locate yours, then if a channel is less busy go in your wireless router’s settings and move to that one.

If they are all busy, last option is to buy a router that supports more recent standard, labeled “ABGN” (even now “AC”) or 5Ghz. Most high end phones and laptop support it as well. That range has around 20 usable channels instead of 3.

Another common issue in public places is when some people can’t connect at all but other people don’t have any issue. This is usually due to a mechanism called DHCP that allocates an address (here you can see it as a slot) to your device. Default settings are made for small networks and remember slots for a long time even if they are not used anymore. It’s usually possible to reduce the “remember” time and/or enlarge the pool of slots in the router’s settings.

Wired

These are less complicatedto troubleshot. You can start by unplugging everything else connected to your router and see if it’s better. If not the issue might come from that box. Also be careful not to create physical loops in your network (like plugging 2 cables between your router and a switch).

Continue reading on blog.mozilla.org