Wireless NetworkingWireless Networking

Chapter 16Chapter 16

• Explain wireless networking standards • Describe the process for implementing Wi-

Fi networks • Describe troubleshooting techniques for

wireless networks

ObjectivesObjectives

• Historic/Conceptual – Wireless network uses radio waves as the media • Convenient • Sometimes the only network option • Same OSI layers as wired networks • Same [upper layer] protocols • Different methods for accessing the media • IEEE 802.11 wireless Ethernet standard

– Wi-Fi – Most common implementation

• Wi-Fi Standards – Wi-Fi IEEE 802.11 • 802.11a • 802.11b • 802.11g • 802.11n

• Certified by Wi-Fi Alliance – 300 member companies – Design and manufacture wireless networking

products – Certification should ensure compatibility

between manufacturers – Troubleshooting section at end of this chapter

brings out proprietary nature of some devices

• 802.11 – Standards define how wireless devices

communicate – Some define how to secure communication – Each sub-standard has name of a IEEE

subcommittee • Wireless Fidelity (Wi-Fi)

• Wireless Network Modes – Ad hoc mode

• Also called peer-to-peer mode • Uses a mesh topology • Independent Basic Service Set (IBBS)

– Two or more wireless nodes communicating in ad hoc mode • Infrastructure mode

– Uses one or more access points – Similar to a wired star topology – Basic service set (BSS)

• Served by a single WAP

• CSMA/CA – Carrier sense multiple access/collision avoidance

(CSMA/CA) – Access method to allow multiple devices to share

network media – Review how CSMA/CD works for wired networks • Each device listens on media – If no or low signal, media is free – If signal above a threshold, media is busy

• If media is busy, device waits the length of the current frame plus the interframe space (IFS) period

• Wireless Networking Security – Problem • Easy-to-install devices have no default security • Network data packets are in radio waves

– Easy to capture – Easy to read

• Three wireless security methods – MAC Address Filtering • Limits access to specific NICs • “Accepted users” list of MAC addresses • List in table stored in WAP • Data packets with other MAC addresses are rejected

– Wireless Authentication • Only users with proper credentials have access • Can use a centralized security database (like Active

Directory) • Requires extra steps for wireless users

– Data Encryption • a. Data Encryption Using WEP

– Wired Equivalent Privacy (WEP) – 64- or 128-bit encryption algorithm – Scrambles data packets – Problems

» Easily cracked » Only works on two lowest OSI network layers