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Chapter 7

Wireless LAN Topologies. Chapter 7. Outline. Wireless Networking Topologies WWAN – WMAN – WPAN – WLAN 802.11 Topologies Access Point Client Station Distribution System (DS) Wireless Distribution System (WDS) Service Set Identifier (SSID) Basic Service Set (BSS)

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Chapter 7

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  1. Wireless LAN Topologies Chapter 7

  2. Outline • Wireless Networking Topologies • WWAN – WMAN – WPAN – WLAN • 802.11 Topologies • Access Point • Client Station • Distribution System (DS) • Wireless Distribution System (WDS) • Service Set Identifier (SSID) • Basic Service Set (BSS) • Basic Service Set Identifier (BSSID) • Basic Service Area (BSA) • Extended Service Set (ESS) • Independent Basic Service Set (IBSS) • Nonstandard 802.11 Topologies • 802.11 Configuration Modes • Access Point Modes • Client Station Modes

  3. Wireless Networking Topologies • Wireless Wide Area Network (WWAN) • Wireless Metropolitan Area Network (WMAN) • Wireless Personal Area Network (WPAN) • Wireless Local Area Network (WLAN)

  4. Wireless Networking Topologies • Wireless Wide Area Network (WWAN) • WWAN also covers broad geographical boundaries but obviously uses a wireless medium instead of a wired medium • WWAN typically use cellular telephone technologies. • Some examples of these cellular technologies are GPRS, CDMA, TDMA, and GSM.

  5. Wireless Networking Topologies • Wireless Metropolitan Area Network (WMAN) • WMAN provides coverage to a metropolitan area such as a city and the surrounding suburbs • WMAN is defined by the 802.16 standardthat defines broadband wireless access and is sometimes referred to as World-wide Interoperability for Microwave Access (WiMAX)

  6. Wireless Networking Topologies • Wireless Personal Area Network (WPAN) • WPAN is a wireless computer network used for communication between computer devices within close proximity of a user • The most common technologies in wireless personal area networks are Bluetooth and infrared • The best example of 802.11 radios being used in a wireless personal area networking scenario would be as peer-to-peer connections.

  7. Wireless Networking Topologies • Wireless Local Area Network (WLAN) • WLAN provide networking for a building or campus environment • The 802.11 standard is defined as a WLAN technology

  8. 802.11 Topologies • The 802.11 standard defines three separate 802.11 topologies • Basic service set (BSS) • Extended service set (ESS) • Independent basic service set (IBSS) • Nonstandard topologies • Bridging, repeating, workgroup bridging, and mesh networking

  9. 802.11 Topologies • Simplex and Duplex review • Simplex • Half – duplex • IEEE 802.11 wireless networks use half-duplex communications • Full - duplex

  10. 802.11 Topologies • Access point • The CWNP definition of an access point (AP) is a half-duplex device with switch-like intelligence • Client Stations • A radio card that is not used in an access point is typically referred to as a client station

  11. 802.11 Topologies • Distribution System (DS) • Wireless traffic can be destined back onto the wireless medium or forwarded onto what is called the distribution system (DS) • Distribution System Medium (DSM) • A logical physical medium used to connect access points • Distribution System Services (DSS) • System services built inside an access point usually in the form of software

  12. 802.11 Topologies • Wireless Distribution System (WDS) • WDS can connect access points together using what is referred to as a wireless backhaul

  13. 802.11 Topologies • Service Set Identifier (SSID) • SSID is a network name used to identify an 802.11 wireless network • Basic Service Set (BSS) • The communicating devices that make up a BSS are solely one access point (AP) with one or more client stations. • Stations that are members of a BSS are termed as “associated”

  14. 802.11 Topologies • Basic Service Set (BSS)

  15. 802.11 Topologies • Basic Service Set Identifier (BSSID) • The 48-bit (6-octet) MAC address of an access point’s radio card is known as (BSSID) • The BSSID address also plays a role in directing 802.11 traffic within the basic service set. • The BSSID address is also used as a unique identifier of the basic service set. • The BSSID address is also needed during the roaming process

  16. 802.11 Topologies • Basic Service Area (BSA) • The physical area of coverage provided by an access point in a BSS is known as the BSA

  17. 802.11 Topologies • Extended Service Set (ESS) • An extended service set is two or more basic service sets connected by a distribution system • The purpose behind an ESS with partially overlapping coverage cells is to provide seamless roaming to the client stations. • Most vendors recommend cell overlap of 15 to 20 percent to achieve successful seamless roaming. • The network name of an ESS is often called an ESSID

  18. 802.11 Topologies • ESS, seamless roaming and nomadic roaming

  19. 802.11 Topologies • Independent Basic Service Set (IBSS) • The radio cards that make up an IBBS network consist solely of client stations, and no access point is deployed • An IBSS can, however, have multiple client stations in one physical area communicating in an ad-hoc fashion

  20. 802.11 Topologies • Independent Basic Service Set (IBSS)

  21. 802.11 Topologies • Nonstandard 802.11 Topologies • Wireless bridging: 802.11 radios can be used to connect two wired networks together using a wireless bridged link • Workgroup bridge (WGB): acts as a gateway for a small wired workgroup, yet the workgroup bridge is a client station associated with an access point • Repeater is a special access point that forwards the data of client stations to a root access point • Wireless mesh routersare essentially a combination of multiple repeaters using proprietary layer 2 routing protocols

  22. 802.11 Configuration Modes • Access Point Modes • Bridge mode • The AP is converted into a wireless bridge. • Workgroup Bridge mode • The AP is transformed into a workgroup bridge. • Repeater mode • The AP performs as a repeater access point. • Scanner mode • The access point radio is converted into a sensor radio allowing the access point to integrate into a wireless intrusion detection system (WIDS) architecture.

  23. 802.11 Configuration Modes • Client Station Modes • Infrastructure mode • Clients that are configured in this mode may communicate, via the AP, with other wireless client stations within a BSS • Ad-Hoc mode • Client cards set to Ad-Hoc mode participate in an independent basic service set (IBSS) topology and do not communicate via an access point. • All station transmissions and frame exchanges are peer-to-peer

  24. The END Chapter 7

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