Chapter 5 - section 5.4 - given a scenario, troubleshoot common performance issues.

section 5.4

Objective – Performance and Wireless Issues

• Congestion and contention
• Bottlenecking
• Bandwidth
▸ Throughput capacity
• Latency
• Packet loss
• Jitter
• Wireless issues
▸ Interference
▸ Channel overlap
▸ Signal degradation or loss
▸ Insufficient wireless coverage
▸ Client disassociation issues
▸ Roaming misconfiguration

Congestion and Contention

• Too many devices sharing network resources
• Causes slow performance
• Common on shared media
• Results in packet delays and drops

Bottlenecking

• Network segment limits overall performance
• Often caused by slow links or devices
• Throughput limited to weakest point
• Common exam troubleshooting scenario

Bandwidth

• Maximum data capacity of a link
• Measured in Mbps or Gbps
• Does not equal actual speed
• Limited bandwidth causes congestion

Bandwidth – Throughput Capacity

• Actual data successfully transmitted
• Lower than bandwidth due to overhead
• Affected by congestion and errors
• Exam distinguishes bandwidth vs throughput

Latency

• Time delay for data to travel
• Measured in milliseconds (ms)
• High latency affects VoIP and gaming
• Caused by distance and processing delays

Packet Loss

• Data packets dropped before reaching destination
• Caused by congestion or errors
• Leads to retransmissions
• Degrades application performance

Jitter

• Variation in packet arrival time
• Major issue for VoIP and video
• Caused by congestion and latency changes
• Results in choppy audio/video

Wireless Issues – Interference

• External signals disrupt wireless transmission
• Common sources: microwaves, Bluetooth
• Reduces signal quality
• Causes retries and drops

Wireless Interference – Channel Overlap

• Multiple APs use same or overlapping channels
• Causes contention and interference
• Common in 2.4 GHz band
• Use non-overlapping channels (exam tip)

Wireless – Signal Degradation or Loss

• Weak signal due to distance or obstacles
• Walls and metal reduce signal strength
• Causes slow speeds or disconnects
• Requires AP placement optimization

Wireless – Insufficient Coverage

• Dead zones without adequate signal
• Caused by poor AP placement
• Results in connectivity issues
• Solved with additional APs

Wireless – Client Disassociation Issues

• Clients randomly disconnect from AP
• Caused by weak signal or interference
• Affects user experience
• Common troubleshooting issue

Wireless – Roaming Misconfiguration

• Clients fail to switch APs smoothly
• Causes dropped connections
• Common in enterprise WLANs
• Requires proper roaming settings

N10-009 Sample Questions – Performance & Wireless

• Q: What metric measures variation in packet delay?
▸ A: Jitter
• Q: What causes multiple APs to interfere with each other?
▸ A: Channel overlap
• Q: What is the difference between bandwidth and throughput?
▸ A: Throughput is actual data transferred
• Q: What issue causes dead zones in wireless networks?
▸ A: Insufficient wireless coverage