Network Performance and Troubleshooting Lecture

Network Performance Issues

• Common problem: "Network is slow"
  • Often, the network is functioning correctly.
  • Responsibility of network administrators to identify communication bottlenecks.

Protocol Analyzers

• Used to capture and analyze network frames.
• Types of Protocol Analyzers:
  • Built-in Capture Tools: Available in switches, routers, firewalls.
    • Can output results for analysis.
  • Third-Party Tools: E.g., Wireshark.
    • Provides detailed protocol decodes and conversation details.
• Applications:
  • Capture all packets for later analysis.
  • Useful in IT security and network troubleshooting.

Network Scanning Tools

Nmap (Network Mapper)

• Gathers information about:
  • Open port numbers.
  • Operating system types and versions.
  • Services running on ports.
• Features:
  • Active scan: Sends queries and examines responses.
  • Can scan entire IP address ranges.
  • Maps out network devices and configurations.
  • Includes scripting engine for extended capabilities.
  • Provides data on unexpected open ports for further investigation.

Discovery Protocols

• Used to gather information about network devices.
• Cisco Discovery Protocol (CDP):
  • Specific to Cisco devices.
  • Provides configuration data without logging in.
• Link Layer Discovery Protocol (LLDP):
  • Vendor-neutral.
  • Supported by most switches.
• Protocol decodes can reveal:
  • IP addresses and port numbers.
  • Device software details and VLAN configurations.

Bandwidth and Speed Testing

• Importance of knowing available bandwidth.
• Speed Testing:
  • Measure time to send data for download/upload assessments.
  • Useful for pre/post network change evaluations.
  • Perform tests at different times to assess bandwidth fluctuations.
• Speed Test Resources:
  • Local ISP-provided tests (e.g., Xfinity, AT&T) for accuracy.
  • Third-party sites: fast.com, speedof.me, speedtest.net, testmy.net.
  • Consider site location and bandwidth constraints for accurate results.