Slow internet with Google DNS since this weekend

[fido...@gmail.com]

So I have been using google dns for a few years and this weekend I noticed my internet was slower than normal

I troubleshooted my computer, router and modem and was not able to fix it

I then put my dns back to my defaut ISP and low and behold my speeds where back up to normal

I can reproduce everytime

Im using Videotron for my ISP in Montreal canada

I can reproduce the issue with various devices connected to my router (tablets, ipad, phones, computers)

Not sure what to do at this point other than keep my ISP DNS

I have a 120MB down/20MB up connection

See screenshot for comparison. This is on same computer and same connection a few min apart after switching DNS

Im using a Netgear R7000 with firmware V1.0.7.6_1.1.99 but also tested dd-wrt.K3_R7000 and tested various speed test sites also

I have no special settings that changed and been running V1.0.7.6_1.1.99 by default for about a month. Issue only started this weekend

Any ideas?

[fido...@gmail.com]

Also in case anyone is wondering I tested on the following

Computer running windows 8.1 with latest chrome, firefox and IE
Tested with computer running Ubuntu 16.04.1 LTS and firefox
Tested on iPad with safari on iOS 10.2 with various speed test apps like Speedtest.net by Ookla/FAST Speed Test by Netflix, Inc.
Tested on Samsung tablet T800 running 6.0.1 ran speed test via various speed test apps such as Simple Speed Check by SpeedSpot.org/Speedtest.net by Ookla/FAST Speed Test by Netflix, Inc.
Tested on Samsung S7 Edge SM-G935W8 running 6.0.1 and ran speed test via various speed test apps such as Simple Speed Check by SpeedSpot.org/Speedtest.net by Ookla/FAST Speed Test by Netflix, Inc.

Lastly I purchased a google onhub to test it and same issue

[Alex Dupuy]

DNS itself is unlikely to directly affect your download or upload speeds.

One possible reason for a change in performance from a speed test tool is that it is using DNS to get a "nearby" IP address to use for testing, and the domain it is using to get the list of IPs does not support EDNS Client Subnet (RFC 7871). So you end up getting a test IP address that is closer to a Google Public DNS resolver in Council Bluffs, Iowa (one example), than to Montréal, Québec. You could try looking at the IP addresses the speed test tool reports, and run those through on-line GeoIP to see where they are located.

I see from your screenshots that the IP address reported in both cases is the same, I'm guessing that it is (was) yours; the servers in the two cases are marked as being in Laval and Montréal. Even if you are located in Brossard, and Laval is further away geographically, the network interconnection may be faster and more direct (speed of light delays are not significant for servers that close by).

Although you ran the speed tests with a number of different devices, it looks like they are mostly the same tests/services. You may not see a difference in performance due to DNS service with other speed tests, like the DSL Reports speed test (which also measures bufferbloat), or Google's speed test with M-Lab (runs quicker & uses less data, if that matters). I believe neither of these depend on DNS geo-location to determine test IP addresses.

If you still see a difference, even across several completely different speed tests using different sets of servers, there are two possibilities that might cause significant performance differences (although neither is very likely overall). First, there may be a device on your network that is confused by a response (or lack thereof) from Google Public DNS to some DNS lookup it makes, that causes it to repeat the query at a very high rate. Secondly, it could be that there is some kind of botnet or other malware on your network that depends on DNS lookups to get in contact with its controller, and Google Public DNS is not blocking the domains it uses, but your other DNS provider is blocking them. In either of these cases, you could look for a "top-talkers" display on your router to identify devices that are sucking up bandwidth.

[fido...@gmail.com]

I setup mac filtering on my router and only allowed 1 device at a time to test and the results where the same.

So I ran a few tests like that and several devices and had the same issue

Since only 1 device was connected I ruled out others causing the issue

Also the devices used such as ipad and android phone and ubuntu I suspect dont have malware and if they did they shouldn't all have the same kind

I know DNS shouldn't do this but since last weekend it is.

For now ill stick with my ISP

[thomas...@gmail.com]

Ditto here. Often, especially apps would take a long time to connect when using the Google DNS. Returning to "obtain automatically" always remedies the issue.

For whatever reason, Google isn't acknowledging this to an issue but I noticed way back in the early 2000s. I tried again recently to see if things have changed, but nope. They haven't.