Content Overview Compared to wired LANs, wireless LANs (WLANs) have unique characteristics. First, the physical characteristics of a wireless LAN introduce range limitations and unreliable media, dynamic topologies where stations move about, interference from outside sources, and the inability for every device to ‘hear’ every other device within the WLAN. From the point of view of WLAN scalability, this module covers two key considerations concerning the scalability of wireless networks: QoS and security. In the past, WLANs handled the transport of low-bandwidth, data application traffic. Today, with the expansion of WLANs into enterprise and vertical (retail, finance, education) markets, WLANs are now used to transport high-bandwidth, intensive data applications in conjunction with time-sensitive multimedia applications. This requirement has led to the necessity for wireless QoS. This module begins by describing how Cisco has met the challenges of QoS deployment in WLANs. With increased reliance on WLANs, businesses are becoming more concerned about network security. Network managers need to provide end users with freedom and mobility without offering intruders access to the WLAN or the information sent and received on the wireless network. The rest of this module describes wireless security standards and the importance of wireless LAN (WLAN) security. It also defines and describes the 802.1x standard and various authentication processes. The module concludes with a description of basic WLAN management and configuration tasks using the Cisco Wireless Control System (WCS). Web Links Is Your WLAN Ready for Voice?
http://www.cisco.com/en/US/netsol/ns340/ns394/
ns348/networking_solutions_white_paper0900ae
cd80472e80.shtml Design Principles for Voice Over WLAN
http://www.cisco.com/en/US/netsol/ns340/ns394/
ns348/networking_solutions_white_paper0900ae
cd804f1a46.shtml The Benefits of Centralization in Wireless LANs
http://www.cisco.com/en/US/products/ps6108/
products_white_paper0900aecd8040f7b2.shtml Understanding the Lightweight Access Point Protocol (LWAPP)
http://www.cisco.com/en/US/netsol/ns340/ns394/
ns348/ns337/networking_solutions_white_paper09
00aecd802c18ee.shtml The Benefits of Centralization in Wireless LANs
http://www.cisco.com/en/US/products/ps6108/
products_white_paper0900aecd8040f7b2.shtml Addressing Wireless Threats with Integrated Wireless IDS and IPS
http://www.cisco.com/en/US/products/hw/modules/
ps2706/products_white_paper0900aecd804f155b.shtml Five Steps to Securing Your Wireless LAN and Preventing Wireless Threats
http://www.cisco.com/en/US/netsol/ns340/ns394
/ns348/ns386/networking_solutions_white_paper09
00aecd8042e23b.shtml Wireless LAN Security White Paper
http://www.cisco.com/en/US/netsol/ns340/ns394
/ns348/ns386/networking_solutions_white_paper09
186a00800b469f.shtml Security of the WEP algorithm
http://www.isaac.cs.berkeley.edu/isaac/wep-faq.html Cisco Wireless Control System (WCS)
http://www.cisco.com/en/US/products/ps6305/
products_data_sheet0900aecd802570d0.html User Guide for the CiscoWorks WLSE and WLSE Express 2.13
http://www.cisco.com/en/US/products/sw/
cscowork/ps3915/products_user_guide_book
09186a008061ab4f.html Cisco Wireless Control System Configuration Guide, Release 4.0
http://www.cisco.com/en/US/products/ps6305/
products_configuration_guide_book09186a008
06b57ec.html

Content 6.1 Implementing WLAN QoS 6.1.1 A Standard for WLAN QoS WLANs, whether they are overlays to or substitutes for traditional wired LANs, are based on standard 802.11. The 802.11 standard extends 802.3 to the wireless domain, though with some complications. Figure depicts a typical WLAN extension to a wired LAN and highlights areas that require special consideration:

Both WLANs and wired LANs define the physical and data link layers and use MAC addresses.
LANs and WLANS use many of the same protocols and applications. Examples of such protocols are the IP and IPsec protocols for VPNs. Examples of applications are web, FTP, and Simple Network Management Protocol (SNMP).
WLANs use carrier sense multiple access with collision avoidance (CSMA/CA) technology instead of the carrier sense multiple access with collision detection (CSMA/CD) technology that Ethernet LANs use. Collision detection is not possible in wireless applications because a sending station cannot receive at the same time that the station is transmitting and, therefore, cannot detect a collision. Wireless 802.11 LANs try to avoid collisions instead of dealing with them after the fact, as is the case in 802.3. Wireless 802.11 uses a Distributed Coordination Function (DCF) to avoid collisions with the use of radio frequency (RF) carrier sense, interframe spacing, and random wait timers to avoid collisions.
LANs commonly use Layer 3 differentiated services code point (DSCP) or Layer 2 802.1p to ensure priority and provide quality of service (QoS). WLANs can use 802.11e. The original 802.11 standards aimed to provide best effort data communication without QoS support. The new 802.11e standard is an extension of 802.11 that provides more consistent, quality RF transmission for voice and video.
802.11 devices operate either in a peer-to-peer fashion or integrated with an existing wired LAN.
802.11 devices often operate within overlapping 802.11 WLANs.
The mobility requirements of 802.11 devices must be met if operation from moving vehicles is to be considered.
802.11 must