1. Local Area Networks Chapter 17, Exploring the Digital Domain

2. In this chapter... the characteristics and advantages of LANs how devices in LANs are connected and transmit data how communication is organized among competing nodes how software facilitates networks ways to extend LAN size and performance how wireless LANs are organized and communicate You will learn about

3. Basic Characteristics of LANs connectivity supporting two-way communication resource sharing limited geographical area transparency of use support from hardware and software

4. Costs and Benefits communications management control cost-effectiveness need for additional equipment maintenance support staff costsbenefits

5. Transmission Media twisted-pair cable UTP CAT-n coaxial cable optical fiber cable infrared transmission radio frequency broadcasting cellular network transmissions bounded mediaunbounded media

6. Topologies star bus ring star topology has a single node that serves as the hub and central switching node for the rest of the network

7. Topologies bus bus topology is a single medium on which all of the nodes are connected

8. Topologies ring a ring topology is a closed path that is directional; signals are passed from node to node

9. Media Access Control Ethernet (AKA “Carrier Sense Multiple Access with Collision Detection”) nodes listen for silence on the bus when carrier is silent, node transmits packet if no collisions, transmission continues but if collisions, backoff procedure invoked

10. Media Access Control Token Passing node can capture a free token packets are transmitted via token to successor token transmitted from node to node “acknowledged” token eventually returned to sender

11. Media Access Control token passing

12. Networking Software physical layer supports basic carrier signals data link layer manages point-to-point connectivity network layer routes data from sender to destination transport layer provides messaging services applications layer provide user functions

13. Extending LANs REPEATERS: boost signal strength over medium BRIDGES: isolate LANs from unnecessary traffic, but connect LANs to neighboring networks SWITCHES: provide dedicated and shared connections for large numbers of nodes ROUTERS: connect same or different protocol nets

14. Extending LANs

15. Wireless LANs infrared broadcasting radio frequency broadcasting spread spectrum (cell telephony) direct sequence spread spectrum (DSSS) frequency hopping spread spectrum (FHSS)

16. WLAN Topology Basic Service Set (BSS) access points (AP) Stationary nodes mobile

17. WLAN Topology ad hoc network temporary nodes mobile transitory

18. WLAN Standards HomeRF 2.4 GHz, 2 - 10 Mbps, 100-150 ft. Wi-Fi (802.11b) 2.4 GHz, 2 - 11 Mbps, 200 - 400 ft. 802.11a 5 GHz, up to 54 Mbps 802.11g 2.4 GHz, up to 54 Mbps

19. Personal Area Networks PAN -- a group of digital devices assembled in a small area to communicate and share information Bluetooth 2.4 GHz, 1 Mbps FHSS up to 7 simultaneous connections