[MacTUG] Macs vs Minuwet

[Steve Hellyer]

ANd to help Mike get good network traces here's how to capture a full  
packet network trace on Mac OS X....

Open up Terminal and type:

sudo tcpdump -K -i en1 -s 0 -w trace.dmp

The -K tells tcpdump not to  verify TCP checksums.  The “-i” specifies  
the network interface (make sure your capture wireless interface), the  
“-s 0” means to capture the entire packet, and “-w trace.dmp” means to  
write it out to a file called trace.dmp.  This file will end up on the  
root of you own home folder.

If your not sure the interface you can open up Network Utility in the  
utilities folder and you can see the various interface there.

Use control - C to quit the packet trace capture.  These files can get  
big rather quickly so I recommend .zip archiving them before sending  
them or coping to a server share.

Steve

On 8-Jun-09, at 6:54 PM, Mike Patterson wrote:

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> Group,
> Sorry, this is long.  You can skip it if issues regarding wireless
> authentication and authorization on Macs don't interest you.
>
> I've been told that at a previous MacTUG meeting, it was decided[0]  
> that
> since MinUWet was placed into enforcement mode, the Mac wireless
> experience has become worse.  I'd like to address this.
>
> I'm not certain how it's possible for MinUWet to cause issues with  
> Macs.
> While there is a MinUWet client for Macs, the only platform which is
> required to run it is Windows.  From a client perspective, what should
> happen with a Mac is this:
> 1 connect to the uw-wireless SSID
> 2 get an IP address
> 3 fire up web browser
> 4 authenticate in the captive portal
> 5 redirect to https://minuwet.uwaterloo.ca
> 6 minuwet website determines that you're on a Mac, using a combination
> of the user-agent string and a piece of Javascript that runs on the  
> client
> 7 client is placed in post-minuwet mode.
>
> It works the same for Linux and other non-Windows hosts.  Windows  
> hosts
> get asked to run the MinUWet client in what would be step 5a.  There  
> is
> nothing about this process that should be hostile to Macs, or any  
> other
> non-Windows platforms.  If anything, Windows users have a complaint  
> that
> they're underserved, but we all know why we're targeting their  
> platform.
>
> I assume that the consensus (about poorer performance for Macs on
> wireless) came about as a result of the issues on the 25th of May.   
> What
> happened then, and has been happening since, is nothing to do with  
> Macs,
> or even MinUWet per se.
>
> As some of you may know, the issues of the 25th were related to a
> network routing loop that caused the backend systems to have delayed  
> or
> interrupted communications with the wireless controllers.[1]  In other
> words, the issue affected all wireless users equally.
>
> I know there were some issues today as well (morning of the 8th of  
> June)
> and I am, quite frankly, mystified.  I changed something that  
> shouldn't
> have had any effect and the complaints slowed, but that could just be
> because people gave up altogether, I don't know.  :)  I do know that
> Monday mornings seem worst, and we're doing the best we can to keep an
> eye on things, but debugging this sort of problem is rather difficult,
> particularly with incomplete information.
>
> All of this being said, I would be *extremely* interested in evidence
> that Mac performance has been suffering wrt wireless.  I don't want to
> seem to be a pain about this, but what evidence would be required  
> would
> be things like traffic captures (preferably full-content) along with
> ntp-sycned timestamps, userids used, and MAC addresses.  We need to be
> able to correlate logs on several different systems in order to find  
> any
> cause.
>
> [0] - perhaps 'decided' is a bad word to use, but I'm not sure what  
> fits
> better.  Group consensus?  A majority, vocal minority?  Without having
> been there I can't say.
> [1] - for further information on how the backend works, you can  
> refer to
> my presentation slides from the IST PD seminar I gave a couple of  
> months
> ago: http://ist.uwaterloo.ca/~mpatters/Presentations/ 
> Wireless40.pdf .  I
> realize that this presentation is a bit light on technical detail.   
> I do
> have more detailed docs but they're terrible and not really suited for
> public dissemination.  Contact me if you'd like to see them anyway.
>
> Thanks,
>
> Mike
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