With mandatory rates, the higher you go the more issues you can see and the advantages of more airtime suffer diminishing returns. Since the lowest mandatory is where control frames get sent, it can have some pretty serious impact. Pushing higher than 24 should be done with some good airtime analysis that most controllers won't give you. When you watch Mac laptops spam control frames like RTS and BAR at 6Mbps and it go unack'd from the AP because of data rates, things can go sideways pretty fast. For more resiliency, keeping lower OFDM rates enabled helps clients with poor supplicants have good experiences.
And most NMS and controllers can't see the issues because the AP isn't registering the frames sent at unsupported rates. This leads to performance issues that you probably won't see and are hard to quantify. Trimming DSSS and HR-DSSS rates (1,2,5.5,11) are a good idea if you can, but I would advise getting crazy trimming rates beyond that. My general recommendation is 12Mbps as minimum in 2.4GHz and 6 as the minimum for 5GHz. This is a reasonable starting place with good overall device compatibility. Obviously in LPV and stadiums are exceptions to this advise. Thanks Jake Snyder Sent from my iPhone > On Jun 21, 2016, at 7:44 PM, James Andrewartha <jandrewar...@ccgs.wa.edu.au> > wrote: > >> On 21/06/16 12:06, Anthony Croome wrote: >> Exactly, use 24Mbs to avoid weird behaviour. >> >> We looked at this a few years ago and found that XP could not handle >> management packets being sent at 48Mb/s or 54Mb/s despite the card >> connecting at 450Mb/s on 5GHz N or 144Mb/s on 2.4GHz N. >> >> On 5GHz the laptop could get an IP address but could not ping it's gateway. >> On 2.4GHz the laptop could get an IP, it could ping it's gateway, but it's >> performance was terrible. >> >> What we saw from a 5GHz packet capture was the AP continuously sending RTS >> to the client but never getting any packets from the client. On 2.4GHz it >> would reply but only after a random number of RTS were sent. > > I saw a similar situation recently, a new laptop with an Intel AC > chipset was sending continuous RTS at 2Mbps (on 2.4GHz), however the AP > was configured with an 11g protection rate of 11Mbps. Setting that to > 2Mbps and the client could talk fine. > > -- > James Andrewartha > Network & Projects Engineer > Christ Church Grammar School > Claremont, Western Australia > Ph. (08) 9442 1757 > Mob. 0424 160 877 > > ********** > Participation and subscription information for this EDUCAUSE Constituent > Group discussion list can be found at http://www.educause.edu/groups/. ********** Participation and subscription information for this EDUCAUSE Constituent Group discussion list can be found at http://www.educause.edu/groups/.
