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Certified Wireless Network Administrator (CWNA) PW0-105. Chapter 12 WLAN Troubleshooting. Chapter 12 Overview. Layer 2 Retransmissions 802.11 Coverage Considerations Voice vs. Data Performance Weather. 2. Certified Wireless Network Administrator: CWNA – PW0-105. Layer 2 Retransmissions.
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Certified Wireless Network Administrator (CWNA) PW0-105 Chapter 12 WLAN Troubleshooting
Chapter 12 Overview • Layer 2 Retransmissions • 802.11 Coverage Considerations • Voice vs. Data • Performance • Weather 2 Certified Wireless Network Administrator: CWNA – PW0-105
Layer 2 Retransmissions • Retransmissions occur when the sending STA does not receive an ACK frame from the target STA • Layer 2 retransmissions impact performance • Increase overhead • Increase latency and jitter • Real-time applications are impacted most by retransmissions • All communications are slower 3 Certified Wireless Network Administrator: CWNA – PW0-105
Layer 2 Retransmissions Causes • RF Interference • Multipath • Adjacent Channel Interference • Low SNR • Mismatched Power Settings • Near/Far • Hidden Node 4 Certified Wireless Network Administrator: CWNA – PW0-105
RF Interference 5 Certified Wireless Network Administrator: CWNA – PW0-105
Multipath 6 Certified Wireless Network Administrator: CWNA – PW0-105
Adjacent Channel Interference 7 Certified Wireless Network Administrator: CWNA – PW0-105
Low SNR 8 Certified Wireless Network Administrator: CWNA – PW0-105
Mismatched Power Settings 9 Certified Wireless Network Administrator: CWNA – PW0-105
Near/Far 10 Certified Wireless Network Administrator: CWNA – PW0-105
Hidden Node (Obstruction) 11 Certified Wireless Network Administrator: CWNA – PW0-105
Hidden Node (Large Coverage Cell) 12 Certified Wireless Network Administrator: CWNA – PW0-105
Hidden Node (Distributed Antenna System) 13 Certified Wireless Network Administrator: CWNA – PW0-105
Hidden Node (RTS/CTS) 14 Certified Wireless Network Administrator: CWNA – PW0-105
802.11 Coverage Considerations • Dynamic Rate Switching (DRS) • Roaming • Layer 3 roaming • Co-channel interference • Channel Reuse/Multiple Channel Architecture (MCA) • Single Channel Architecture (SCA) • Capacity vs. Coverage 15 Certified Wireless Network Administrator: CWNA – PW0-105
Voice vs. Data 16 Certified Wireless Network Administrator: CWNA – PW0-105
Performance • Transmission power rates • Antenna gain • Antenna type • Wavelength • Free space path loss • Physical environment • CSMA/CA • Encryption • Application use • Number of clients • Layer 2 retransmissions 17 Certified Wireless Network Administrator: CWNA – PW0-105
Weather • Lightning • Wind • Water • Air stratification • UV/Sun 18 Certified Wireless Network Administrator: CWNA – PW0-105
Chapter 12 Summary • Layer 2 Retransmissions • 802.11 Coverage Considerations • Voice vs. Data • Performance • Weather 19 Certified Wireless Network Administrator: CWNA – PW0-105