4. Spectrum is limited, so use as much as you can. In an era of immense distrust in government, lets give credit where credit is due. The decision of government policy makers to designate portions of the electromagnetic spectrum for use by unlicensed wireless devices stimulated the development of the Wi-Fi technologies we use today. Unfortunately, radio spectrum with the best propagation characteristics is extremely valuable, so we don't get so much of it for Wi-Fi. Even during the early days of wireless, I strongly encouraged enterprises to deploy dual-band (2.4 GHz and 5 GHz) products. Unfortunately, far too many network designers saw this as a choice of one or the other, and 2.4 GHz usually won. That's still true to a certain extent today, but most enterprises have gotten the message. The only way to scale Wi-Fi performance in the enterprise is to use all available spectrum.
5. Interference is a design reality. I remember the early days of Ethernet networks when media-related problems were often at the root of performance and reliability problems. Those problems were pretty much solved as UTP and fiber interconnect technology improved. But interference-related media challenges on Wi-Fi networks will never go away, despite vendor efforts to automate channels and power levels. Interference from other networks, within and outside your facility, is still a big issue. Using 5 GHz spectrum is currently the best way to combat that problem, but as usage increases, interference will still need to be mitigated. And then there's the worst case scenario, physical-layer RF jamming attacks. These denial of service attacks cannot be prevented. The best hope is quick identification and mitigation.
6. Wi-Fi is a LAN, not a WAN technology. From the beginning, I was skeptical about the notion of metro area Wi-Fi networks. There were lots non-technical reasons I never bought into this movement, including policy considerations about government ownership and competition as well as untenable business plans. But mostly, my concerns were technical in nature. The 802.11 standard was designed as a contention-based protocol for small-cell LANs. While it can be made to work across wide areas, doing so introduces a range of design and operational challenges and often requires extremely high density of AP's. It was clear from the beginning that vendors weren't being honest about this and many communities were sold on promises that didn't pan out. That doesn't mean Wi-Fi isn't effective in hot-spots, like retailers or even hot-zones, like public parks. It's just not reliable enough for wide area deployments.
7. Wireless Security is all about risk and reward. When 802.11 products first hit the market, I wrote about how WEP was broken. At that time, the encryption algorithms in WEP hadn't yet been cracked, but the shared-key architecture simply wasn't viable for enterprise deployments. Give Cisco credit for implementing the first dynamic 802.11 security system based on 802.1X, EAP, and RADIUS, technology that eventually was standardized in 802.11i. It's a great security architecture, but it doesn't meet all needs. In particular, most enterprises find it increasingly necessary to accommodate guest access to their WLAN. When implementing guest access, network segmentation is almost always a better strategy. Yes, there is some additional risk, but that's the price we sometimes have to pay in order to make a network easy to use.
8. Most Wi-Fi users need nomadic rather than mobile services. Since Wi-Fi came to market at a time when cell phone adoption was rapidly increasing, it's no surprise that mobility has always been a focus of product engineering efforts. Vendors have long touted their products' ability to provide seamless mobility on enterprise networks, a claim that has almost always had a few asterisks associated with it. But the reality is that WLAN adoption has largely been an issue of convenience, providing users with nomadic data services as they carry their laptop computers (and more recently, Wi-Fi enabled smartphones) from office to conference room to home.