[LUGSB] How to fix wireless reliability problems on campus

Wed Sep 14 12:09:18 EDT 2011

Dear Tony,

They help me. Is wireless working for you with them set to off or are
they set to auto for you by default?

Would you share the output of the following commands on your system?

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

Yours truly,
Richard Yao

On Wed, Sep 14, 2011 at 11:29 AM, Tony Biondo <tonyb at tonybox.net> wrote:
> 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
>>>>>> >>
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>>>>>
>>>>
>>>>
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