Why am I getting latency between my modem and my router?

Question

I pay for a 15mbps down, 1mbps up DSL internet plan from TekSavvy Solutions (Canada). At least once or twice a week there will be moments where we get speeds much lower than advertised.

When I notice the internet is particularly slow I test this by doing a Speedtest(.net). Often times the download speed is between 6mbps and 13mbps, sometimes as low as 2mbps.

I play the game League of Legends where I will experience random spikes in ping throughout my playing time. The ping rarely remains stable across consecutive days without variation of ~10ms-20ms.

While troubleshooting a ping issue with League of Legends in which the ping spikes over 100ms I completed a series of troubleshooting steps, one of which revealed a 41ms latency between my modem and my router.

This problem surfaced a couple months ago and it was suggested I replace my 5 year old D-Link router, which I did. It appears the router replacement did not solve the latency between the modem and the (new) router.

I have also used the Android app "Wifi Analyzer" to ensure my router is on an optimal channel. The app shows I have nearly -40dBm signal and using the best possible channel.

I am tired of trying to solve this problem every 3-4 weeks and would love to finally end all of these internet issues.

How can I find out what is causing the latency, and how can I finally solve it?

Answer 1

When using WIFI you will always be at the whimm of those arround you - you really need to switch to a wired connection to guarantee a stable, low latency connection to your router. Its quite probable that even when using the best WIFI channel other channels with overlap and interfere with your performance. (there are only 3 non-overlapping channels in the 2.4 gig band). Just because its the best channel does not mean its good enough !

Also, in a home user scenario, a cabled connection will have a lower latency (and more bandwidth) then a WIFI connection.

You may also want to get a variant of MTR (winmtr is for Windows I think), which can tell you where the latencies are coming in. The problem could also be that your computer is not fast enough [ at least that used to be the case when I played online games - sometime in the dark ages ].

The problem is almost certainly not double NAT as this would not have a significant impact on latency.

Answer 2

There may not actually be a problem with your modem. Since the network stack isn't necessary for a modem, it might just be that your modems OS is either shoddy or runs on inadequate hardware.

On the other hand, I wouldn't use a separate modem with a modern router, at least not, if it has a built in modem for the DSL-standard you're using.

With the information you have given, there are still some basic things you can try:

• Make sure your modem is actually a modem and not a mis-marketed/-labeled router - that would change potential causes and solutions
• Connect to your router via Ethernet cable. Your WiFi shouldn't be a problem at -40dBm, but one never knows.
• If that doesn't help, try pinging different destinations. At least here in Germany, local (tech) news sites tend to have great latency. If other destinations respond as expected, i.e. within your regular window of 10-20ms
• Make sure your have no computers with malware in your network. Depending on what that malware does, it can use a lot of bandwidth and that can, depending on your router, increase your pings by a lot.
• Similarly, make sure you have no freeloaders on your network.
• Replace your modem. I have had better experiences with routers with built-in modems than separate ones, but that might be different for you.
• There may be problems that are out of your reach. DSL is a wonderfully simple technology when it comes to cables: it only needs a twisted pair of relatively thin wires. That, however, makes it susceptible to magnetic fields of electrical wires, for example. Usually that would be more obvious, since current on electrical wires is less infrequent. However, if your phone line runs parallel and close to a line that is used only by a washing machine, for example, and that washing machine is used very rarely, you would see increased ping times, increased packet losses and, of course, reduced bandwidth. Your DSL provider should be able to test the line quality, if the problem continues for at least an hour during business hours, if their support nows their stuff.