Module 6 Review Exam

Bandwidth and Throughput Capacity

• Bandwidth refers to the maximum theoretical data capacity transmitted over a network connection, typically measured in bits per second (bps)
• Throughput is the amount of data successfully transmitted across a network in a given period, including all data packets (application-level and overhead)
• Goodput is a subset of throughput focusing only on successfully delivered application-level data, excluding retransmissions and protocol overhead
• Data rate refers to the raw data transmission speed, including all bits (application-level and overhead), typically measured in bits per second (bps)

Example Scenario

• Imagine transferring a 1 GB file over a network with 1 Gbps bandwidth and a data rate of 900 Mbps
• The network is capable of 1 Gbps (maximum theoretical capacity)
• The server transmits data at 900 Mbps, including all bits (overhead and application data)

Troubleshooting Bandwidth and Throughput Capacity

• If throughput is significantly lower than throughput capacity, explore these factors:
  • Congestion: Monitor traffic using tools like NetFlow, Wireshark, or SNMP to identify high-bandwidth devices. Implement QoS policies to prioritize critical traffic and reduce congestion. Segment large networks into smaller subnets or VLANs to reduce congestion. Upgrade bandwidth if congestion persists.
  • Hardware Constraints: Verify that network devices (switches, routers, NICs) support the required speeds.
  • Retransmissions: Monitor error rates using monitoring tools to identify specific links with errors. Check physical connections (cables, connectors, ports) for damage or loose connections. Optimize protocol settings (e.g., TCP window sizes, flow control) to improve reliability. Replace unreliable links (e.g., old copper cables) with fiber optics.
  • Protocol efficiency: Analyze protocol overhead and packet sizes. Optimize protocols (e.g., TCP/IP settings like window size or segmentation) for better efficiency.
  • Device Limitations: Check device capabilities to ensure they support adequate bandwidth. Inspect device performance to identify resource constraints (e.g., CPU or memory usage) influencing high-load scenarios.

Troubleshooting Latency

• Latency is the delay for data to travel from source to destination; measured in milliseconds (ms)
• Common Causes and Solutions:
  • Distance: Use content delivery networks (CDNs) or edge servers.
  • Congestion: Prioritize latency-sensitive traffic using QoS.
  • Device Processing: Ensure devices (routers, firewalls, switches) have sufficient processing power for required data rates.
  • Protocol Overhead: Use tools (like Wireshark) to identify protocol overhead and inefficient packet sizes. Optimize protocols for better efficiency.

Troubleshooting Jitter

• Jitter is the variation in latency between data packets.
• Causes and Solutions:
  • Network Congestion: Manage traffic congestion, increase network bandwidth, or use VLANs.
  • Device Overload: Ensure devices (routers, switches, etc.) have sufficient processing power to handle traffic.

Troubleshooting Congestion and Contention

• Congestion occurs when network, or system capacity is exceeded.
• Contention happens when multiple devices compete for the same network resources
• Causes and Solutions:
  • High Bandwidth: Prioritize critical traffic using QoS policies; schedule bandwidth-intensive tasks (e.g., backups) during off-peak hours to reduce congestion.
  • Upgrade the network connection by increasing its speed (e.g., from 100 Mbps to 1 Gbps). Implement link aggregation, to spread traffic, and reduce congestion.

Troubleshooting Wireless Performance

• Causes and Solutions
  • Co-Channel Interference: Use non-overlapping channels or ensure all APs use the same SSID and security settings.
  • Adjacent Channel Interference: Use non-overlapping channels or transition devices to 5GHz or 6Ghz bands for less interference.
  • Channel Overlap: Adjust the transmission power of APs to avoid overlap, configure APs to use non-overlapping channels, Conduct a wireless site survey to optimize AP placement, and improve signal coverage.
  • Environmental Interference: Move APs or devices away from sources of interference (e.g., microwaves, Bluetooth devices). Use shielded equipment in high-interference environments. Use 5 GHz or 6 GHz bands (less prone to interference)
  • Insufficient Coverage: Deploy more APs, use mesh network systems to create more coverage, or improve signal range of existing APs
  • Interference from other devices: Position APs or devices away from sources of interference.
  • Client Device Limitations: Replace outdated devices that lack support for modern standards (e.g., Wi-Fi 6 or Wi-Fi 6E), enable smart roaming or band steering on client devices.
  • Overcrowded Frequency Bands: Use less congested frequency bands to prevent interference from overlapping networks.
  • Poor Access Point Placement: Place APs closer to key areas, in open spaces, or on walls/ceilings to improve signal distribution.
  • Hardware or Device Issues: Upgrade network devices or use more capable wireless devices.

Tools and Protocols

• Ping: Tests connectivity by sending ICMP echo requests, measures latency, identifies packet loss and DNS resolution
• Traceroute/Tracert: Maps the path packets take across a network, identifies points of failure or delays
• Nslookup: Resolves domain names to IP addresses and IP addresses to domain names, queries DNS records, and checks DNS server response times
• Dig: Performs DNS lookups, providing more detailed output than nslookup.
• Tcpdump: Captures and analyzes network traffic, identifies traffic patterns and protocol usage
• Netstat: Displays information about network connections, listening ports, routing tables, and statistics
• Ip/Ipconfig/Ifconfig: Manage and view network interface configurations, IP addressing, and routing
• Arp: Resolves IP addresses to MAC addresses on a local network
• Nmap: Used for discovering devices, mapping networks
• Wireless Tools: Netspot, Ekahau, HeatMapper, and others
• Cable Tester: Checks the integrity of copper or fiber optic cables
• Taps: Monitors network traffic without disrupting the network
• Visual Fault Locators (VFL): Identifies breaks or faults in fiber optic cables.
• Networking Device Commands (e.g., show mac-address-table, show route, show interface, show config, show arp, show vlan, show power): Monitor device performance and operational status; diagnose and resolve issues, verify configuration