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Vidar Stokke Senior Engineer at the Norwegian University of Science and Technology, IT-division, Networking
Programme:1.History of wireless networks at NTNU2.The wireless network with standalone APs3.The wireless network with controller based APs4.Pros and cons of controller based networks
Controller based wireless networksController based wireless networks
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History of WLAN at NTNU
• 2004/2005: 250 autonomous APs (802.11b og g)• Hotspot coverage
– public areas and meeting rooms
– Approx 20% coverage
• Authentication by web portal (HP) and/or VPN (Cisco)• Challenges:
– Time consuming administration– No mobility– Capasity issues due to many users on few AP– Web portal did not scale
• 1100-1200 associated clients
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The ”Wireless Campus” project – with lightweight APs• The goal was ”100%” wireless coverage in NTNU’s
buildings.• Started Q3 2006 and terminated Q3 2008• The process:
– Site survey (External company)
– Wiring and AP mounting (3 different electrical contractors)
– PoE-switch installation in wiring cabinets (NTNU IT)
• Resulted in approx 1400 APs, 18 wireless controllers and 100 PoE switches
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The ”Wireless Campus” project – with lightweight APs• In 2011:
– 1800 APs
– 20 controllers
– 10.000 simultaneous clients at peak hours
– Approximately 300.000 sqm coverage
• Deployment of controller based wireless network was a success
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A comparison of standalone and lightweight/controller based wireless
• Standalone– Everything on and through the AP
• Traditional lightweight – Everything on and through the controller
• Hybrid lightweight– Almost everything on and through the controller, but with a certain
flexibility
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Wireless with standalone APs
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Wireless with lightweigh APs
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Wireless with lightweight APs and H-REAP
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AP join process - discovery
• Ways to discover controllers– Layer 2 broadcast on local subnet
– List of previously known controllers
– OTAP (Over The Air Provisioning) – removed from Ciscos SW
– DHCP option 43
– DNS lookup for ”cisco-capwap-controllers.domain”
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AP join process - CAPWAP
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Mobility groups
• Several controllers can join one mobility group• Client roaming across different controllers and APs
– Without loosing connection
– Without the need to reauthenticate
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Mobility groups
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Auto-RF
• Each controller is part of an RF network– APs connected will forward RRM-info to its controller about other
APs it sees.
– Adjusts channel and power assignment based on leaders computations
• One controller is the leader of the RF domain– Collects necessary RRM-info from other controllers
– Tries to avoid neighbour APs on same channel and interference
– Calculates and computes the best possible channel and power assignment for the different APs
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Rogue detection and containment• APs not within the RF-domain is marked as rogue
• Possible to do a joint effort to take them down– Up to 4 APs join together
– Send diassociation messages to the connected clients
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Downsides with lightweight
• Get stuck with one brand (ie. Cisco)– Even though CAPWAP opens for third-party components
• Harder to do hardware upgrades on APs and/or controller– Controller and APs need to support each other
• Expensive with a low number of APs
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Benefits of lightweight solution
• Easier management/configuration of a large number of APs:– All configuration done at controller and pushed to APs
• Major changes done by the click of a button
– Software upgrade done from controllers and deployed to APs
– PlugNPlay of new APs and replacement APs
• Radio Resource Management (RRM)– Auto-RF
– Client load balancing
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Benefits of lightweight solution
• Better mobility for clients– Due to mobility groups
• Improved overview of the wireless network– Client information and debugging– AP statistics– AP and client alarms
• Location based services (requires WCS)– NTNU Campusguiden
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A demo?
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Questions?