CWNA Chapter 10 – WLAN Architecture

My Notes from chapter 10 of the CWNA study guide

Wireless LAN client devices

  • 802.11 Radio form factors
    • 802.11 radios are used in both client NICs and access points.
    • External Radios
      • Many form factors, meaning the NIC comes in different shapes and sizes:
        • PCMCIA adapter/PC card
        • Express Card
        • USB
    • Internal Radios
      • Installed inside the device
      • Mini PCI
      • Mini PCI Express
    • Mobile Devices
      • Smartphones
      • Tablets
      • Bar code scanners
      • VoWiFi phones
    • Wearables
      • Google Glass
      • Fitbit
      • Etc.
    • Internet of Things (IoT)
  • 802.11 Radio chipsets
    • A group of integrated circuits designed to work together is often marketed as a chipset.
    • Some chipsets may only support the ability to transmit on the 2.4 GHz ISM band; other chipsets can transmit on either the 2.4 GHz or 5 GHz unlicensed frequencies
    • Many proprietary technologies turn up in the individual chipsets, and some of these technologies will become part of the standard in future 802.11 amendments.
  • Client utilities
    • End user must have the ability to configure a wireless client NIC
    • Software interface is needed in the form of client utilities
    • Three major types, or categories, of client utilities exist:
      • Integrated operating system client utilities
      • Vendor-specific client utilities
      • Third-party client utilities
  • Management, control and data planes
    • Telecommunication networks are often defined as three logical planes of operation:
      • Management Plane
        • WLAN Configuration
          • configurations of SSIDS, security, WMM, channel, and power settings.
        • WLAN Monitoring and Reporting
          • Monitoring of layer 2 statistics like ACKs, client associations, resassociations, and data rates occurs in the management plane
        • WLAN Firmware Management
          • The ability to upgrade access points and other WLAN devices with the latest vendor operational code is included here
      • Control Plane
        • Dynamic RF
          • Coordinated channel and power settings for multiple access points
          • Dynamic RF is also referred to by the more technical term radio resource management (RRM).
        • Roaming Mechanisms
          • Support for roaming handoffs between access points
          • L3 roaming, maintaining stateful firewall sessions of clients, and forwarding of buffered packets
        • Client Load Balancing
          • Collecting and sharing client load and performance metrics between access points to improve overall WLAN operations
        • Mesh Protocols
          • Routing user data between multiple access points requires some sort of mesh routing protocol.
      • Data Plane
        • Where user data is forwarded
        • A standalone AP handles all data forwarding operations locally
        • In a WLAN controller solution, data is normally forwarded from the centralized controller, but data can also be forwarded at the edge of the network by an AP.

WLAN architecture

  • Autonomous WLAN architecture
    • The conventional access point was a standalone WLAN portal device where all three planes of operation existed and operated on the edge of the network architecture
    • All configuration settings exist in the autonomous access point itself
    • All encryption and decryption mechanisms and MAC layer mechanisms also operate within the autonomous AP.
    • An autonomous access point contains at least two physical interfaces: usually a radio frequency (RF) radio card and a 10/100/1000 Ethernet port.
    • Autonomous APs are deployed at the access layer and typically are powered by a PoE capable access layer switch.
  • Centralized network management systems
    • A WNMS moves the management plane out of the autonomous access points.
    • Provides a central point of management to configure and maintain thousands of autonomous access points.
    • Network management server (NMS) is now used more often
  • Cloud networking
    • Applications and network management, monitoring, functionality, and control are provided as a software service
    • The two most common cloud networking models are as follows:
      • Cloud-Enabled Networking (CEN)
        • The management plane resides in the cloud, but data plane mechanisms such as switching and routing remain on the local network
      • Cloud-Based Networking (CBN)
        • The data plane is also moved to the cloud with the intent of eliminating hardware other than that used to access the Internet at the local network
  • Centralized WLAN architecture
    • Central WLAN controller that resides in the core of the network.
    • Autonomous APs have been replaced with controller-based access points, also known as lightweight APs or thin APs
    • All planes were moved out of access points and into a WLAN controller
    • Encryption and decryption capabilities might reside in the centralized WLAN controller or may still be handled by the controller-based APs, depending on the vendor
    • Some time-sensitive operations are still handled by the AP
    • WLAN Controller:
      • WLAN controllers are often referred to as wireless switches
      • Some vendors use proprietary protocols for communications between the WLAN controller and their controller-based
      • APs.
      • Many WLAN vendors use the Control and Provisioning of Wireless Access Points (CAPWAP) protocol for managing and monitoring access points
      • Can support multiple BSSIDs and VLANs
  • Distributed WLAN architecture
    • Cooperative access points are used, and control plane mechanisms are enabled in the system with inter-AP communication via cooperative protocols.
    • A distributed WLAN architecture combines multiple access points with a suite of cooperative protocols, without requiring a WLAN controller
    • The control plane information is shared between the APs using proprietary protocols
  • Unified WLAN architecture
    • Fully integrating WLAN controller capabilities into wired network infrastructure devices
  • Hybrid architecture
    • Hybrid of any of the above

Specialty WLAN infrastructure

  • Wireless workgroup bridge
    • Is a wireless device that provides wireless connectivity for wired infrastructure devices that do not have radio cards.
    • WGB is an associated client of the access point, the WGB does not provide connectivity for other wireless clients


  • Wireless LAN bridges
    • The purpose of bridging is to provide wireless connectivity between two or more wired networks.
    • Wireless bridges support two major confi guration settings: root and nonroot.
    • A bridge link that connects only two wired networks is known as a point-to-point (PtP) bridge


  • A point-to-multipoint (PtMP) bridge link connects multiple wired networks


  • A common problem with point-to-multipoint bridging is mounting the high-gain omnidirectional antenna of the root bridge too high. The result is that the vertical line of sight with the directional antennas of the nonroot bridges is not adequate.


  • Enterprise WLAN router
    • A distributed solution using enterprise-grade WLAN routers at each branch office is a common choice.
    • WLAN routers are very different from access points. Unlike access points, which use a bridged virtual interface, wireless routers have separate routed interfaces
  • Wireless LAN mesh access points
    • Wireless mesh APs communicate with each other by using proprietary layer 2 routing protocols and create a self-forming and self-healing wireless infrastructure (a mesh) over which edge devices can communicate


  • WLAN array
    • Xirrus offers a proprietary solution that combines a WLAN controller and multiple access points in a single hardware device known as a Wi-Fi array
    • Access-point radios using sector antennas and an embedded WLAN controller all reside in one device
    • WLAN arrays are also useful in high user density environments and can also be used to reduce cable runs
  • Virtual AP system
    • A virtual access point solution uses multiple access points that all share a single basic service set identifier (BSSID).
    • Clients stations believe they are connected to only a single access point, although they may be roaming across multiple physical APs
  • Real-time location systems
    • Network management servers (NMSs), WLAN controllers and WIDS solutions have some integrated capabilities to track 802.11 clients by using the access points as sensors
  • VoWiFi
    • VoIP over WiFi.

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