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McGraw-Hill ©2003 The McGraw-Hill Companies, Inc.
Chapter 10
Local Area NetworksPart 2:
Wireless and Virtual LANs
McGraw-Hill ©2003 The McGraw-Hill Companies, Inc.
Understand the different transmission techniques used in Understand the different transmission techniques used in wireless LANs.wireless LANs.
Understand the main characteristics of IEEE 802.11 wirelessUnderstand the main characteristics of IEEE 802.11 wirelessLANs.LANs.
Understand the applications of IEEE 802.11.Understand the applications of IEEE 802.11.
Understand the characteristics of 802.15 LANs and the Understand the characteristics of 802.15 LANs and the Bluetooth technology that implements this standard. Bluetooth technology that implements this standard.
After reading this chapter, the reader should After reading this chapter, the reader should be able to:be able to:
OOBJECTIVESBJECTIVES
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OOBJECTIVES (continued)BJECTIVES (continued)
Understand the applications and rationale for VLANs.Understand the applications and rationale for VLANs.
Understand the concept of virtual LANs.Understand the concept of virtual LANs.
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WIRELESSWIRELESSLANsLANs
WIRELESSWIRELESSLANsLANs
10.110.1
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Figure 10-1
ISM bands
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Figure 10-2
FHSS
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Figure 10-3
DSSS
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IEEE 802.11:IEEE 802.11:RF LANsRF LANs
IEEE 802.11:IEEE 802.11:RF LANsRF LANs
10.210.2
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Figure 10-4
BSS
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Figure 10-5
ESS
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Technical Focus:Technical Focus: Portable versus MobilePortable versus Mobile
In networking two terms are used to define nonstationary devices: portable and mobile.
The term portable means that a device may move from one location to another, but it remains in a fixed place when in use.
The term mobile means that the station can move during operation.
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Technical Focus:Technical Focus: Hidden Node ProblemHidden Node Problem
In a wired Ethernet, when a station sends a frame, every station connected to the shared medium senses (hears) the signal; stations are not hidden (electronically) from each other. On the other hand, in a wireless network, two stations may be separated from each other by a physical barrier (such as a wall). They are hidden (electronically) from each other.
In this case, both of these stations may start sending a frame at the same time without sensing the signal coming from the other station. In other words, a collision may occur without either station detecting it. This means that the CSMA/CD access method, which is based on the detection of a collision by the sender, does not work here.
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Technical Focus:Technical Focus: Wireless LAN AddressingWireless LAN Addressing
The addressing mechanism in a wireless LAN is more complicated than in a wired LAN. In a wireless LAN a frame may travel from a station to another station in the same BSS, or from a station in one BSS to another station in another BSS.
In the second case, the frame journey is made of three trips: from the source station to the AP of the source BSS, from the AP of the source BSS to the AP of the destination BSS, and from the AP of the destination BSS to the destination station.
For this reason, a wireless frame has four address fields.
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IEEE 802.11:IEEE 802.11:INFRARED LANsINFRARED LANs
IEEE 802.11:IEEE 802.11:INFRARED LANsINFRARED LANs
10.310.3
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Figure 10-6 Infrared point-to-point LAN
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Figure 10-7
Infrared diffused LAN
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IEEE 802.15:IEEE 802.15:BLUETOOTH LANsBLUETOOTH LANs
IEEE 802.15:IEEE 802.15:BLUETOOTH LANsBLUETOOTH LANs
10.410.4
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Figure 10-8Piconet
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Figure 10-9
Scatternet
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Business Focus:Business Focus: BluetoothBluetooth
Bluetooth was named after the king of Denmark, who triedto unite all of the Baltic Region countries (Denmark, Sweden, Norway, and Finland). He united Denmark and Norway, but was killed by his son in 986.
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VIRTUALVIRTUALLANsLANs
VIRTUALVIRTUALLANsLANs
10.510.5
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Figure 10-10
A switch connecting three segments
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Figure 10-11
A switch using VLAN software
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Figure 10-12
Two switches in a backbone using VLAN software
