McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Chapter 10 Local Area Networks Part 2: Wireless and Virtual LANs

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Understand the different transmission techniques used in wireless LANs. Understand the main characteristics of IEEE wireless LANs. Understand the applications of IEEE Understand the characteristics of LANs and the Bluetooth technology that implements this standard. After reading this chapter, the reader should be able to: O BJECTIVES

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 O BJECTIVES (continued) Understand the applications and rationale for VLANs. Understand the concept of virtual LANs.

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 WIRELESSLANsWIRELESSLANs 10.1

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 10-1 ISM bands

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 10-2 FHSS

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 10-3 DSSS

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 IEEE : RF LANs IEEE : RF LANs 10.2

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 10-4 BSS

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 10-5 ESS

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Technical Focus: Portable 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.

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Technical Focus: Hidden 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.

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Technical Focus: Wireless 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.

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 IEEE : INFRARED LANs IEEE : INFRARED LANs 10.3

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 10-6 Infrared point-to-point LAN

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 10-7 Infrared diffused LAN

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 IEEE : BLUETOOTH LANs IEEE : BLUETOOTH LANs 10.4

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 10-8 Piconet

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure 10-9 Scatternet

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Business Focus: Bluetooth Bluetooth was named after the king of Denmark, who tried to 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.

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 VIRTUALLANsVIRTUALLANs 10.5

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure A switch connecting three segments

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure A switch using VLAN software

McGraw-Hill©The McGraw-Hill Companies, Inc., 2000 Figure Two switches in a backbone using VLAN software