CWNA Chapter 7 – Wireless LAN Topologies

My Notes from chapter 7 of the CWNA study guide

Wireless networking topologies

  • Wireless wide area network (WWAN)
    • Provides RF coverage over a vast geographical area
    • Typically use cellular telephone technologies or proprietary licensed wireless bridging technologies
    • Some examples of these cellular technologies are general packet radio service (GPRS), code division multiple access (CDMA), time division multiple access (TDMA), Long Term Evolution (LTE), and Global System for Mobile Communications (GSM)
  • Wireless metropolitan area network (WMAN)
    • Provides RF coverage to a metropolitan area such as a city and the surrounding suburbs
    • Worldwide Interoperability for Microwave Access (WiMAX)
  • Wireless personal area network (WPAN)
    • Is a wireless computer network used for communication between computer devices within close proximity of a user
    • Most common technologies in WPANs are Bluetooth and infrared
    • Peer-to-peer connections.
  • Wireless local area network (WLAN)
    • Local area networks provide networking for a building or campus environment

802.11 topologies

  • Access point
    • Access point (AP) was a half-duplex device with switchlike intelligence
    • “Thin/ Lightweight” refer to Aps that are controller based for the switchlike intelligence
    • Autonomous Aps have the switchlike intelligence
  • Client station
    • Any radio that is not used in an access point is typically referred to as a client station
    • Laptops, tablets, scanners, smartphones, and many other mobile devices
    • Client stations must contend for the half-duplex RF medium in the same manner that an access point radio contends for the RF medium
  • Integration service (IS)
    • A frame format transfer method
    • Because the wired infrastructure is a different physical medium, an 802.11 data frame payload must be effectively transferred into an 802.3 Ethernet frame
    • The integration service mechanism normally takes place inside a WLAN controller when 802.11 user traffic is tunnelled back to a WLAN controller
  • Distribution system (DS)
    • Is used to interconnect a set of basic service sets (BSSs) via integrated LANs to create an extended service set (ESS)
    • Distribution System Medium (DSM) A logical physical medium used to connect access  points is known as a distribution system medium (DSM). The most common example is an 802.3 medium.

chapter7-1

  • Wireless distribution system (WDS)
    • A mechanism for wireless communication using a four-MAC-address frame format
    • Bridging, repeaters, and mesh networks are real world WDS examples
    • A WDS can connect access points together using what is referred to as a wireless backhaul
    • Can use one radio for backhall and client access but results in degraded throughput as RF is shared medium
    • Can also backhall on 1 band and provide access on another or both.

chapter7-2
chapter7-3

  • Service set identifier (SSID)
    • A logical name used to identify an 802.11 wireless network
    • SSID can be made up of as many as 32 characters and is case sensitive
    • You can hide the SSID but this is a very weak security not defined under the 802.11-2012 standard
  • Basic service set (BSS)
    • The cornerstone topology of an 802.11 network
    • Communicating devices that make up a BSS consist of one AP radio with one or more client stations
    • Stations that are members of a BSS have a layer 2 connection and are called associated
    • In the typical BSS, client stations cannot communicate directly with each other unless they go through the AP
  • Basic service set identifier (BSSID)
    • 48-bit (6-octet) MAC address of an access point’s radio is known as the basic service set identifier (BSSID).
    • The proper definition is the layer 2 identifier of each individual BSS
  • Basic service area (BSA)
    • The physical area of coverage provided by an access point in a BSS is known as the basic service area (BSA)
    • The size and shape of a BSA depends on many variables, including AP transmit power, antenna gain, and physical surroundings
  • Extended service set (ESS)
    • Two or more basic service sets connected by a distribution system medium
    • No requirement for BSAs to overlap to provide seamless roaming
  • Independent basic service set (IBSS)
    • The radios that make up an IBSS network consist solely of client stations (STAs), and no access point is deployed
    • Can have multiple client stations in one physical area communicating in an ad hoc fashion
    • All of the stations transmit frames to each other directly and do not route their frames from one client to another.
    • all stations must be transmitting on the same frequency channel.
  • Mesh basic service set (MBSS)
    • The mesh functions are used to provide wireless distribution of network traffic, and the set of APs that provide mesh distribution form a mesh basic service set (MBSS).
  • QoS basic service set (QoS BSS)
    • QoS mechanisms can be implemented within all of the 802.11 service sets
    • QoS enhancements are available to QoS STAs associated with a QoS access point in a QoS BSS

802.11 Configuration modes

  • Access point modes
    • Bridge Mode
      • AP radio is converted into a wireless bridge
      • Adds extra MAC-layer intelligence to the device and gives the AP the capability to learn and maintain tables about MAC addresses from the wired side of the network.
    • Workgroup Bridge Mode
      • Provides wireless backhaul for connected 802.3 wired clients
    • Repeater Mode
      • Extends the coverage area of a portal AP on the same channel
    • Mesh Mode
      • AP radio operates as a wireless backhaul radio for a mesh environment
    • Scanner Mode
      • AP radio is converted into a sensor radio, allowing the AP to integrate into a wireless intrusion detection system (WIDS) architecture
  • Client station modes
    • Infrastructure mode
      • The client station will allow communication via an access point
    • Ad Hoc mode
      • Participate in an IBSS topology and do not communicate via an access point
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