[LUGSB] How to fix wireless reliability problems on campus

[Richard Yao]

Dear Ahmed,

Not all drivers support these settings. In my case, I use the iwlagn
driver, which does not support "auto". You can try it on your hardware
and check that the setting is reflected in the output of iwconfig.
These settings actually hurt performance in areas where you only have
a handful of devices using Wi-Fi, so implementing "auto" in Linux
wireless drivers so that these settings are only used when necessary
would be a good idea.

As I said in my first email, I plan to take this to the kernel mailing
list. As an addendum, I request that everyone send me the output of
the following commands and information on whether or not this helps.

cat /etc/lsb-release
lspci -n
uname -srvmpio

That way I will have some of idea of where it helps and where it
doesn't before I talk to the kernel developers about this.

Here are some references that have more information on these subjects:

http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Linux.Wireless.mac.html
http://www.arnetminer.org/viewpub.do?pid=36668

Yours truly,
Richard Yao

On Wed, Sep 14, 2011 at 10:41 AM, Ahmed Hassan <ahmed at linuxism.com> wrote:
> Where did you read from?
> Why don't you make it auto instead?
>
>
> On Wed, Sep 14, 2011 at 10:34 AM, Ahmed Hassan <ahmed at linuxism.com> wrote:
>>
>> RTS/CTS adds a handshake before each packet transmission to make sure that
>> the channel is clear.
>>
>> Fragmentation allows to split an IP packet in a burst of smaller fragments
>> transmitted on the medium
>>
>> http://linux.die.net/man/8/iwconfig
>>
>> On Wed, Sep 14, 2011 at 10:30 AM, Tony Biondo <tonyb at tonybox.net> wrote:
>>>
>>> What exactly do these settings do?
>>>
>>> On Wed, Sep 14, 2011 at 9:37 AM, Richard Yao <ryao at cs.stonybrook.edu>
>>> wrote:
>>> > Dear Everyone:
>>> >
>>> > For reference purposes, here is a speed test of WolfieNet-Secure after
>>> > doing this:
>>> >
>>> > http://www.speedtest.net/result/1482432493.png
>>> >
>>> > I could not connect to WolfieNet-Secure from my current location
>>> > before I did that tweak, so you can consider any test done prior to my
>>> > tweak to have 0 bandwidth both ways with infinite ping times. For the
>>> > record, my wireless card is an Intel Ultimate-N 6300, so your speeds
>>> > will likely be somewhat slower with wireless G.
>>> >
>>> > Yours truly,
>>> > Richard Yao
>>> >
>>> > On Wed, Sep 14, 2011 at 9:17 AM, Richard Yao <ryao at cs.stonybrook.edu>
>>> > wrote:
>>> >> Dear Everyone,
>>> >>
>>> >> If you have problems connecting to Wi-Fi on campus, try the following:
>>> >>
>>> >> iwconfig wlan0 rts 2347 frag 2346
>>> >>
>>> >> You will want to change the name from wlan0 to whatever your wireless
>>> >> card's name is. You might also want to put it in /etc/local or
>>> >> whatever your distribution's init system stores custom boot commands.
>>> >> It will not fix wireless deadzones like Javits 111, but it should
>>> >> enable you to connect to the campus wireless anywhere anyone else can
>>> >> connect. As an added bonus, your download/upload speeds will be higher
>>> >> too.
>>> >>
>>> >> I had been having issues with wireless reliability on campus since I
>>> >> started using Linux and this semester, the improvements that were made
>>> >> to campus Wi-Fi made it particularly acute. Configuring these settings
>>> >> fixed it for me. Now Network Manager behaves comparably to the Windows
>>> >> Wireless Zero Configuration. It seems that these settings were meant
>>> >> to deal with this exact situation and that Windows has them enabled by
>>> >> default. I assume Mac OS X also had them enabled by default given just
>>> >> how bad things are on campus without them.
>>> >>
>>> >> Let me know if it works for you. If all goes well, I will post to the
>>> >> kernel mailing list in a week or two informing them of the situation
>>> >> so we can get these settings set by default, like on Windows. i.e. You
>>> >> are all guinea pigs.
>>> >>
>>> >> Yours truly,
>>> >> Richard Yao
>>> >>
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>
>
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