Cisco Gets a Case of Throughputitis

Far be it from me to hate on a Wi-Fi vendor...


...but seeing Cisco's Wi-Fi recommendations for iPhones (and other Apple iOS devices) has led me to wonder whether The Cisco (Kid) is a Friend of Mine.

Cisco released a Best Practices doc for supporting iPhones, iPads, et al. back in November.  For whatever reason I missed it back then.  I'm bringing it up now because Keith Parsons had something about it on his Twitter feed and Ekahau has a webinar coming up on designing a Wi-Fi network for iOS devices.  

I am happy that Cisco is bringing up the topic of device-centric Wi-Fi design.  Wi-Fi is (or, at least, should be) all about the end user, and device-centric design implicitly acknowledges this.

I am less happy at several of Cisco's actual recommendations.  They seem to have fallen into the trap of believing (or, more perhaps more accurately, leading) the Latest Trendy Wi-Fi Disease, throughputitis.  

Throughputitis, as you all know, is Latin for "inflammation of the throughput".  It is a common and debilitating Wi-Fi disease whose primary symptom is believing that a fast throughput test is an indication of good Wi-Fi.  

Unfortunately for throughputitis sufferers, higher throughput readings are often an indication of bad Wi-Fi.  Or, to be more specific, unstable Wi-Fi.

In fairness to Cisco, their case of throughputitis is mild.  While they have some Wi-Fi design recommendations that are questionable, they at least acknowledge that throughputitis exists:

Although using 80 MHz wide channel bonding may at first seem to boost an individual client performance, in a high AP density environment, the co-channel interference due to limited spectrum availability can potentially reduce the overall network performance.
That's a quote from Page 10 of Cisco's afore-linked 'Best Practices' document for iOS devices.  The subtext of that quote is that several Wi-Fi infrastructure configuration settings will "boost individual client performance" (meaning, increase throughput tests) while "potentially reduce the overall network performance" (meaning, give you bad Wi-Fi).

So, if Cisco acknowledges throughputitis and wants Wi-Fi folks to avoid it, then why am I complaining?  Because there a lot of Cisco's recommendations will result in throughputitis, anyway.

For example:

-Cisco recommends allowing the controller (WLC) to choose channel width.  In most enterprise environments, that will result in too few APs using 20 MHz wide channels.

-Cisco recommends disabling the 6 Mbps and 9 Mbps data rates.  In most enterprise environments, this will increase the likelihood of co-channel interference (CCI) and, possibly, increase the likelihood of dead zones (meaning, areas where users can connect to Wi-Fi, but can't get online).

-Cisco recommends creating a separate, 5 GHz-only SSID for iOS devices.  When unpredictable physical obstructions (groups of people, "Sit & Stand" desks, etc.) pop up, 2.4 GHz Wi-Fi can be essential for creating a reliable connection for devices (even iOS devices).

I also have quibbles with some of the MAC layer recommendations Cisco is making, but I'll leave those to the experts.  I focus on wireless, and wireless is the physical layer.

I am picking on Cisco a little bit here.  They're far from the only Wi-Fi vendor that suffers from throughputitis.  In fact, they seem to have a milder case than most.  Cisco is the industry leader, so I am holding them to a higher standard.

Cisco has a great Wi-Fi product.  I just wish they'd focus even more on reliability, even if it hurts their throughput tests.

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Comments

  1. Hello Ben, Wondering what's the reasoning behind your thought that disabling 6 & 9 Mb data rates will cause higher CCI? Is your theory the Ap will have to raise it's power to try and cover the area with the higher data rate?

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