[LUGSB] How to fix wireless reliability problems on campus

Wed Sep 14 11:29:38 EDT 2011

Every reference to these settings I can find is on the APs side,
actually, are you sure they are really useful for clients? Perhaps the
auto-detection of these settings is broken in iwlagn or something.

On Wed, Sep 14, 2011 at 11:05 AM, Richard Yao <ryao at cs.stonybrook.edu> wrote:
> Dear Ahmed,
>
> I neglected to mention that I found out about this when
> troubleshooting wireless connectivity problems on campus. There was no
> site that recommended setting these to fix wireless connectivity
> problems, but I remembered seeing them set on Windows, Linksys routers
> and the Verizon Fios router, so I decided to try them and they fixed
> things.
>
> After seeing that they made things better and reading about them in
> greater depth, I did several Google searches to find websites where
> people have suggested using these settings to fix wireless
> connectivity problems. I did not find a single reference and it might
> be that I am the first Linux user to suggest that these settings are
> useful for client devices.
>
> Yours truly,
> Richard Yao
>
> On Wed, Sep 14, 2011 at 10:57 AM, Richard Yao <ryao at cs.stonybrook.edu> wrote:
>> 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
>>>>> >>
>>>>> > _______________________________________________
>>>>> > lugsb mailing list
>>>>> > lugsb at fsl.cs.sunysb.edu
>>>>> > To unsubscribe from this list, go to:
>>>>> > http://www.fsl.cs.sunysb.edu/mailman/listinfo/lugsb
>>>>> >
>>>>> _______________________________________________
>>>>> lugsb mailing list
>>>>> lugsb at fsl.cs.sunysb.edu
>>>>> To unsubscribe from this list, go to:
>>>>> http://www.fsl.cs.sunysb.edu/mailman/listinfo/lugsb
>>>>
>>>
>>>
>>> _______________________________________________
>>> lugsb mailing list
>>> lugsb at fsl.cs.sunysb.edu
>>> To unsubscribe from this list, go to:
>>> http://www.fsl.cs.sunysb.edu/mailman/listinfo/lugsb
>>>
>>
> _______________________________________________
> lugsb mailing list
> lugsb at fsl.cs.sunysb.edu
> To unsubscribe from this list, go to:
> http://www.fsl.cs.sunysb.edu/mailman/listinfo/lugsb
>