School 1:1 Program WLAN Design Considerations

The design of a WLAN to accommodate a school’s 1:1 program can make or break the entire enterprise. A poorly designed WLAN presents connectivity issues, bandwidth issues, co-channel contention, and RF utilization problems that distract end-users from classroom activities and results in a loss of trust in the technology. Similarly, clients with substandard Wi-Fi chipsets will also compromise WLAN performance.

These are some of the important considerations I’ve learned when designing and operating a WLAN to support a school’s 1:1 program.

Wireless LAN

Key points to consider when designing a high-density WLAN to support a 1:1 program:

• 802.11ac is highly desirable, 802.11n is workable and a minimum requirement
• Do a site survey to determine optimal AP placements, but design for capacity, not solely coverage
• Evaluate your switching capacity, including PoE budgets, for AP backhaul
• Establish client SLA’s before designing the WLAN
• 5 GHz radios are required
• DFS channels are required for wide channels or very-high density
• 2.4 GHz becomes a junk band in high density. Use it only for guest/BYOD clients.
• Use band-steering to move clients to the 5 GHz spectrum
• Use the entire 5 GHz spectrum everywhere, and choose channel bandwidths to prevent cell overlap.
  • 80 MHz channels in coverage-areas
  • 40 MHz channels in high-density areas like classrooms
  • 20 MHz channels in really high-density areas such as multi-story classroom layouts
• Disable low data-rates, all the way up to 24 Mbps. Experiment with going higher.
• Reduce maximum AP radio power to limit cell sizes
• Reduce AP radio receive sensitivity to prevent clients at the edge of the cell from associating
• Use load balancing techniques to spread clients evenly among AP’s
• Limit SSID’s to as few as possible, generally no more than three. Try this:
  • 1 SSID with WPA2-Enterprise security for school and BYOD devices
    • Use AAA override/dynamic profile assignment (whatever your vendor calls it) to assign security policies, access control, VLAN’s, and QoS policies via RADIUS attributes
  • 1 SSID with no security for guest access
    • Only use a captive web portal if your school requires it
    • Captive portals are very unfriendly to mobile devices
    • Public Wi-Fi should be fast, free, and easy
• Only use WPA2-Enterprise 802.1X authentication. WPA-PSK is a nightmare if you ever need to change the password.
• Use an MDM solution to distribute Wi-Fi credentials
• Rate-limit guest and BYOD clients
• Use QoS to deprioritize traffic from guest and BYOD clients
• Use layer 7 QoS to deprioritize/rate-limit bandwidth hogs that are not time sensitive including
  • Mac OS, iOS, Chrome OS, and Windows software updates
  • Dropbox, iCloud, and Skydrive syncing
  • Site-specific background data hogs such as an enterprise AV deployment, WSUS server, etc.
• Track the applications used on the WLAN and use layer 7 QoS to deprioritize/rate-limit bandwidth hogs that are time sensitive, but are only used for recreational purposes on the WLAN.
  • Netflix, Pandora, Grooveshark, etc.

Should time allow, many of these points will become blog posts of their own.

Client Devices