Windows, Linux, and other operating systems all have built-in support for IPv6, and it’s enabled by default. According to a myth going around, this IPv6 support is slowing down your connection and disabling it will speed things up.

This myth originally had a grain of truth to it — Firefox 3 handled IPv6 poorly on some computers, especially Linux systems. However, this myth isn’t true — and we even did a benchmark to test it out.

The Myth

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Windows, Linux, and other operating system all have integrated support for IPv6. IPv6 support is activated by default on all systems. However, most people’s connections still use the IPv4 protocol instead of the next-generation IPv6 protocol that solves so many problems with IPv4.

So, the myth goes, having IPv6 enabled slows down your Internet connection. When you connect to a website, your computer will search for the IPv6 address first before finding it’s not available and switching to IPv4. Disable IPv6 and your computer will look up IPv4 addresses immediately, eliminating those little delays.

Where the Myth Came From

Firefox 3 had a problem with IPv6. When IPv6 was enabled, Firefox attempted to resolve DNS addresses with IPv6 first before switching to IPv4. This could add a noticeable delay every time you navigated to a new domain in Firefox. This was a big problems on some Linux systems with Firefox 3 many years ago, so there are still tips going around for disabling IPv6 on Linux to speed up Firefox. Setting the “network.dns.disableIPv6” preference to True on Firefox’s about:config page will disable this IPv6 support, so you can disable it only for Firefox without disabling it system-wide.

Firefox 4 fixed this problem. Firefox will now only use IPv6 DNS lookups if IPv6 is actually functional on your connection. It’s smart enough to handle this on its own. This was just a bug in Firefox 3, and it’s been fixed.

It’s possible that, on networks with misconfigured IPv6 settings, computers might try to contact broken or nonexistent IPv6 DNS servers before falling back to IPv4. If you were on such a network, disabling IPv6 could help you — but it’s very unlikely you’re connected to a network or Internet service provider with such badly configured IPv6 settings at this point.

Problems With Disabling IPv6

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Disabling IPv6 can cause problems. If your Internet connection and router have already migrated to IPv6, you’ll lose the ability to use it properly. IPv6 may also be required for some home networking functions — for example, the easy-to-use Homegroup home networking feature introduced in Windows 7 requires IPv6 enabled on the computers on your home network to use it.

The entire world is moving towards IPv6, although it’s happening too slowly. IPv6 is necessary to replace IPv4 — we’re running out of IPv4 addresses and IPv6 is the solution.

Benchmarks

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According to the myth, disabling IPv6 will speed up DNS requests by eliminating a delay that occurs when your computer checks for an IPv6 address before falling back to IPv4. To benchmark this, we benchmarked DNS requests.

First, we ran namebench with the default settings on a normally configured Windows 8.1 system. IPv6 is enabled on this system, as that’s the default, but the connection has no IPv6 capability. According to the myth, that IPv6 support is slowing us down.

With IPv6 enabled, the benchmark showed the average DNS request speed of the Google Public DNS server was 43.22 ms.

Next, we disabled IPv6 by heading to HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\TCPIP6\Parameters in the registry editor, adding the DisabledComponents value, and setting it to ffffffff as Microsoft’s instructions for disabling IPv6 specify. We then restarted the computer and verified that IPv6 was disabled — no IPv6 interfaces appeared in ipconfig /all.

With IPv6 disabled, the benchmark showed the average speed of the Google Public DNS server was 43.97 ms. It may appear that DNS lookups were actually slower with IPv6 disabled, but this is well within the margin of error. There’s no noticeable slow-down with IPv6 enabled, just normal variations of speed going either way — in this case, it was actually a bit faster with IPv6 enabled.

There’s a good chance you don’t actually need IPv6 on your network — unless you rely on Windows Homegroup or similar features — so it may not be particularly harmful to remove if if you know what you’re doing. However, you won’t see a speed improvement from clinging to IPv4 unless there are serious problems with your Internet service provider’s network or your home network.

Image Credit: thierry ehrmann on Flickr