Wireless and Downloads - explain this !?

Ok, this is strange.

I have a wireless router (ASUS WL-520g), which works fine, but there are some issues about download speeds that doesn´t seem logical to me. It was the same with another router I had, so it´s not that.

An example (there are many others websites like this):

1. Imagine website 1 and website 2, both have the same large file (over 100MB) available for download.

2. I connect my laptop using a cable and get about 220KB/sec download speed, both for website 1 and website 2.

3. I then connect my laptop using wireless, and now it becomes strange:

Website 1 gives me about 206KB/sec (a little lower than cable, but perfectly understandable).

But:

Website 2 gives me only about 80KB/sec (why is the wireless so much slower?).

I don´t get it ? Any thoughts about this ?

 

That prolly means that you are maxing out your wireless's bandwidth with website 1, and thus website 2 does not have enough bandwidth and loads dog slow.

While on cable, you have enough bandwidth to download both websites at 200+ kb/sec, but while on wireless you only have enough bandwidth for 1 website to run at full speed.

What wireless card do you have? Also, are there any interferences between you and the router? If there are a lot, then it explains the limited bandwidth you have allowing you to only load 1 website fast.

 

It all depends on traffic (load) and where you are on the que. Most sites only have a limited uplink speed, which is what's used to send it to you. If you check at a different time your download speed may be higher or lower. It also has to do on how your were routed through all of the switches. One may had taken the senic route, while the other was fighting traffic. Way too may variables. The loly way to know is by doing a trace and see if it takes the same route each time.

 

Please note that the speeds do not change from time to time, and I have a very good connection to the wireless router - I´m using a Dell M65 and an old Dell C400, the speeds are virtually the same for both laptops.

Examples (same file, different servers):

Server A:

cable: 215 kb/s
wireless: 86 kb/s

Server B:

cable: 216 kb/s
wireless: 215 kb/s

 

What are the websites? Are you downloading the files at the same time or one at a time?

 

Dude, like we mentioned before, there is a bandwidth limitation you are hitting. Wired you can run both websites at 200+ kb/sec, but with the wireless you can't do that. Only one will run at that speed, the other cannot.

 

They are client domains, I can PM you the testfiles.

I download one at a time.

adinu, I understand that Wireless is a little slower than cable, my tests show that too, but what doesn´t make sense is why one server is MUCH slower on Wireless while to other is not:

Server A:

cable: 215 kb/s
wireless: 86 kb/s

Server B:

cable: 216 kb/s
wireless: 215 kb/s

 

Also depends on the time of day.. internet traffic? Routers sometimes don't multidownload well vs wired. The router has to send both downloads wirelessly and basically it's overloading.

 

Nope, speeds are basically the same, please note I only download one file at the time, clear my cache, restart and then plugin the other connection, this way I can test my cable vs wireless:

I did another test today, since I now have a faster connection than before (4MB vs 2MB), and now the difference is even clearer than before - check this:

Cable:

256 kb/s server A
415 kb/s server B

Wireless:

76 kb/s server A
405 kb/s server B

I understand that server A is slower than server B, could be a number of reasons, but that doesn´t explain why server A is so much slower on wireless than cable when server B is basically the same using cable or wireless.

Doesn´t make any sense, anyone know where I can ask about this?

 

try using a different browser.

 

Yep, did that too - tried with IE, Firefox and Opera - same results.

It´s so strange....

 

Asuming you are using Windows XP or earlier it is likely due to differences in latency between the two servers - which would show up dramatically over your wireless connection and not so much with the LAN. Starting with Vista, your RWIN (Receive window) is dynamically adjusted where in prior versions of Windows it is static and small.

When your RWIN is small and your connection has a high latency the transmission becomes bogged down with receive acknowledgements being sent back to the server from your computer. I have seen my 6 MB connection bogged down just like yours over wireless. You can find software tools to adjust the RWIN and it can be done manually. A look through DSLReports.com's tools and tweaks will provide means for both. I suggest reading and making the manual adjustment. It's a single, reversable setting in the registry without the need to install software.

 

That´s an explanation I haven´t seen before, I am using Windows XP, do you know exactly which setting in the registry needs to be edited ?

I found this:

http://www.dslreports.com/faq/tweaks/5._RWIN

RWIN: How do I raise/lower mine? (#1629)
Download DrTCP from this page to your desktop. Open it and enter desired value for TCP Receive Window (RWIN). Then click Save, Exit and Reboot your PC so that the change will "take."

 

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters

DWORD TcpWindowSize (value in bytes)

Be sure to read thoroughly. It becomes self defeating to have a RWIN that is too large.

From this Microsoft article:

If you want something quick-and-dirty to try, try using 227,760 (156 x 1460). When modifying the TcpWindowSize parameter select decimal and then just type in 227,760. Judging by the slow speed of that one server (70KB) I have to imagine the latency is high and the above setting should do well to correct it - if the latency is the problem.

Also, remember to reboot Windows between each change to the registry for those changes to take effect.

 

YESSSSS - that was it ! Now my wireless is just as fast (almost) as my cable, amazing, thanks a lot, I owe you a beer !!!!

 

Thank DSL Reports too. I was pulling my hair out with the same problem before I found them. It's one place where "tweaking" actually makes one hell of a noticable difference.

You can expect to some slow servers, though. The catch of a large receive window is trouble over a bad connection. If you have any lost packets, the entire window needs to be retransmitted. The larger the window..... Get a bad connection with multiple retransmits of a large window and throughput drops in a hurry. Nothing is perfect, I guess. Overall, you should be much better with the larger window over wireless.

 

95% of the sites are faster now, best example I have is from 88KB/Sec to 434KB/Sec, just because of this tweak.

Great, I may have to write an article about this.