networking chapter 16
TRANSCRIPT
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