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Difficulty: Very hardWireless Principles and Architecture

An enterprise network deployment uses Cisco Lightweight Access Points (LAPs) operating in a Centralized Split-MAC architecture managed by a Wireless LAN Controller (WLC). During high-density traffic analysis, an engineer must verify which frame processing tasks are handled locally by the AP in real time to minimize latency. Which function is executed directly by the Lightweight AP rather than being processed by the Wireless LAN Controller?

  1. Transmission of 802.11 beacon frames and processing of real-time 802.11 frame acknowledgmentsAnswer
  2. B
    Management of client 802.1X/EAP authentication state machines and key handshake management
  3. C
    Processing of client association and reassociation requests across the broadcast domain
  4. D
    Dynamic Radio Resource Management (RRM) calculations for channel and power assignment

Answer

Transmission of 802.11 beacon frames and processing of real-time 802.11 frame acknowledgments
Under Cisco Split-MAC architecture, time-sensitive (real-time) 802.11 protocol functions are executed directly on the Lightweight Access Point. These include beacon transmission, probe responses, MAC-level frame acknowledgments (ACKs), frame buffering/queuing, and signal strength measurements.

Step-by-Step Solution

1
Analyze the Split-MAC architecture division of responsibilities in Cisco centralized wireless networks.
Split-MAC divides 802.11 protocol handling between real-time MAC functions and management/non-real-time MAC functions.
Real-time functions must react within microsecond thresholds directly on the AP radio hardware.
2
Identify AP-specific real-time MAC functions.
The AP performs beacon generation, probe responses, 802.11 MAC layer acknowledgments (ACK), frame buffering, and Layer 1/2 encryption/decryption.
Sending real-time ACKs or beacons back and forth across a CAPWAP tunnel to a WLC would introduce intolerable latency.
3
Identify WLC-specific management functions.
The WLC manages 802.11 authentication, association/reassociation processing, 802.1X/EAP key handshakes, RRM, and CAPWAP tunnel termination.
Centralizing management policy ensures seamless mobility, central security control, and global RF optimization.

Key Concept

Split-MAC Architecture Division of Responsibilities
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Topics

Wireless Principles and Architecture

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