• Chapter 1: Cisco VOIP Implementations
• Chapter 2: IP Quality of Service
• Chapter 3: Classification, Marking, and NBAR
• Chapter 4: Congestion Management and Queuing
• Chapter 5: Congestion Avoidance, Policing, Shaping, and Link Efficieny Mechanisms
• Chapter 6: Implementing QoS Pre-Classify and Deploying End-to-End QoS
• Chapter 7: Implementing AutoQoS
• Chapter 8: Wireless LAN QoS Implementation
• Chapter 9: 802.1x and Configuring Encryption and Authentication
• Chapter 10: WLAN Management

Chapter 8: Wireless LAN QoS Implementation

Wireless LANs use Carrier Sense Multiple Access with Collision Avoidance (CSMA/CA) as the MAC mechanism.

Collision avoidance is performed by Distributed Coordinated Function (DCF), which employs Inter-Frame Spacing (IFS) and random back-off windows to minimize collisions.

Wireless LAN QoS

WLAN QoS is defined in IEEE 802.11e.

Wireless Multimedia (WMM) was released prior to 802.11e as an interim standard.

WMM provides four access categories, or queues:

• Platinum - Voice
• Gold - Video
• Silver - Best effort (default)
• Bronze - Background

802.11e provides eight priority levels, 0 through 7.

802.11e priorities can be mapped to WMM access categories for backward compatibility:

802.11e and WMM use Enhanced DCF (EDCF) to provide proportional back-off window sizes for each class.

Split-MAC Architecture

The split-MAC architecture separates MAC services to real-time and non-real-time functions.

Real-time functions are performed by Lightweight Access Points (LAPs):

• Beacon generation
• Probe transmission/response
• Power management
• 802.11e/WMM QoS
• Encryption/decryption
• Control frame processing
• Packet buffering

Non-real-time functions are handled by a centralized Wireless LAN Controller (WLC):

• Client association/disassociation
• 802.11e/WMM resource reservation
• 802.1x EAP
• Key management

Lightweight Access Point Protocol (LWAPP) provides tunneling between LAPs and a WLC.

802.11e/WMM QoS values are translated to DSCP values on the LWAPP packet header to ensure end-to-end QoS.