I use FireFox 1.0.6 and Opera 8.02 constantly. They both had been displaying problems of slow access to web sites. After reading this comment I decided to try it and see what happened. It made a huge difference with FireFox under SuSE 9.0. I got a couple of friends to try it out and they did not get the same increase in speed that I did -- though they were using the FireFox and SuSE as I was.
On my system it made a big difference. The difference was in the "pause" right after you clicked on a link and some pauses while loading that are no longer there. It did not change the download speed or anything like that.
It had to be checking for an IPv6 link when it first tried the DNS server. That brought up the question of -- if that is the problem why did this fix only work on my system? I did some research and discovered that the ipv6 thing is not exactly a FireFox problem. Technically FireFox is working correctly. What seems to be the problem can be anyone of three things. Buggy DNS servers, buggy home routers and browser settings.
Some DNS servers are returning ipv4 results for an ipv6 request which causes FireFox to do multiple request -- which is the procedure specified by the standard. Other browsers are ignoring any bad ipv6 responses or considering them the same as no ipv6 address available (except for Opera 8.02) and don't have the delay problem.
Some home routers, which set themselves up as your DHCP and DNS servers, are doing something similar. Wireless routers seem to be the number one problem but regular routers can cause the problem also.
This means that you can get a delay of 4 to 5 seconds when your router is first accessed, then a similar delay when any buggy DNS server that is accessed during the load of a web site, returns a bad ipv6 result. This becomes a problem when the site you visit links you to several other servers that have to be looked up. An example would be the multiple ad servers at Yahoo.
Another issue that screws up figuring this out is that the OS itself could have ipv6 set on or off (mine was off) which means that if it is set to off, any test or anything run from the shell (like wget) will not have this problem. Makes it harder to debug.
I decided to play with my router and see if it was the main problem, since I just switched to DSL with a new router that was built in to the DSL modem. Before I did that, I decided to check my network settings and noticed that the old cable modem DNS servers were still listed in my settings. Since they could be buggy and the problem I decided to put in the new DNS servers used by the DSL provider. While thinking about how to find those IP addresses I noticed that there was an option of: "Update name servers and search list via DHCP" in my network settings. Hmmmmm I thought, this would be a great test to see if it is the router causing the problem since it is the DHCP server.
When I changed the settings to "Update name servers and search list via DHCP" which lets the router decide which DNS servers to use and probably activates a cache in the router -- the speed difference was amazing... Not only for FireFox but for Opera also. Now turning IPv6 on and off in FireFox makes no difference in speed.
Why this made such a difference I don't know but it has something to do with the way the router handles IPv6 when the router is in complete control of serving addresses through DNS. The router/modem is one of the latest, hottest, etc. (and most expensive) and has lots of state of the art features (four port router, wireless built in, DSL2+, etc) and may have advanced DNS selection and usage features (I say may because the manual is buried somewhere). So changing this setting on your system might not make the same speed difference with older routers. But if you are using a router with DSL or cable I recommend that you check your network and DNS server settings and try out "Update name servers and search list via DHCP" if you are not already using it.
Happiness is a hot connection...
