Chapter 10 Monitoring and Troubleshooting

1. Chapter 10 Monitoring and Troubleshooting 10.1 Network Monitoring 10.2 Troubleshooting

2. Chapter 10 Monitor & Troubleshoot 10.1 Network Monitoring • Network monitoring • ensuresa network to function continuously • Aspects include • Server performance • Network statistics • Hard disk performance • Memory usage • CPU utilisation

3. Chapter 10 Monitor & Troubleshoot 10.1.1 Server Performance • Server performance includes • number of queued commands • queued commands = commands awaiting execution • too high → a bottleneck in the server • use additional server • use multiple processors • quality of server sessions • server session records server-client connection • How is the connection broken? • normal logoff, error, or server timeout • server timeout → server overloaded

4. Chapter 10 Monitor & Troubleshoot 10.1.2 Network Statistics • Network statistics include • error rate • number of collisions per second • re-transmission after collision • waiting time will increase greatly • network utilisation • Saturated • utilisation ~100% • →more collisions

5. Chapter 10 Monitor & Troubleshoot 10.1.3 Hard Disk Performance • Hard disk performance includes • disk space remaining • throughput of the hard disk • Throughput = amount of data transferred per second • the speed at which requests are serviced. • number of queued requests • busy or not • Too high → hard disk overloaded

6. Chapter 10 Monitor & Troubleshoot 10.1.4 Memory Usage • Memory usage← rate of memory swapping • Swapping • data not in use are moved from the main memory • onto the hard disk • to make room for new data • Too many swapping → system slows down

7. Chapter 10 Monitor & Troubleshoot 10.1.5 CPU Utilisation • CPU utilisation • average percentage of CPU activity • high (> 90%) → overloaded • or, caused by • low memory • improper configuration

8. Chapter 10 Monitor & Troubleshoot 10.2 Troubleshooting • Common network problems: • response too slow • unable to detect the network from a workstation • unable to login • unable to use resources of the network • unable to connect to the Internet • unable to execute certain programs

9. Chapter 10 Monitor & Troubleshoot 10.2 Troubleshooting • Troubleshooting • to diagnose and fix problems • The structured steps are • establishing the symptoms • identifying the affected area • establishing what has changed • selecting the probable cause • implementing the solution • testing the results • documenting the solution

10. Chapter 10 Monitor & Troubleshoot 10.2 Troubleshooting10.2.1 Establishing the symptoms • Symptoms • are information about a problem • may come from • users • 1. when the problem occurs • 2. what the user is doing when the problem occurred • 3. how often the problem occurs • 4. what has been done to try to correct the problem • 5. what the system has changed recently • error messages or event logs

11. Chapter 10 Monitor & Troubleshoot 10.2 Troubleshooting10.2.2 Identifying the affected area • scope • a single workstation • a network segment (controlled by a hub/bridge/switch) • the entire network • involves network infrastructure • malfunctioning hubs or switches • insufficient bandwidth for the network • highest priority

12. Chapter 10 Monitor & Troubleshoot 10.2 Troubleshooting10.2.3 Establishing what has changed • A network suddenly fails → some changes • Consider: • new software or hardware added? • positions of hardware on the network changed? • e.g. Moved workstation → cabling related issue

13. Chapter 10 Monitor & Troubleshoot 10.2 Troubleshooting10.2.4 Selecting the probable cause • Selecting the probable cause requires • isolating the problem • tools • If a user is unable to log onto the network, probable causes: • invalid logon • faulty cable • bad network card • the account has been locked

14. Chapter 10 Monitor & Troubleshoot 10.2 Troubleshooting10.2.4 Selecting the probable cause • A. Isolating the problem • Techniques • removing cables one by one • shutting down services one after the other • pulling out affected system • check whether it can work as a standalone machine • rebooting the network • last resort

15. Chapter 10 Monitor & Troubleshoot 10.2 Troubleshooting10.2.4 Selecting the probable cause • B. Tools • Cable tester • a device used in checking a cable • Event viewer • a utility program that stores • security threats • e.g. failed log on or failed data access • system activities • application activities • tell how well the system is running

16. Chapter 10 Monitor & Troubleshoot 10.2 Troubleshooting10.2.4 Selecting the probable cause

17. Chapter 10 Monitor & Troubleshoot 10.2 Troubleshooting10.2.4 Selecting the probable cause • B. Tools (cont’) • Protocol Analyzer / Packet Sniffer • is hardware or software • verifies the working of a protocol • captures each packet passing over a network • and decodes its content • Note: packet sniffers may be used by hackers to intercept data

18. Chapter 10 Monitor & Troubleshoot 10.2 Troubleshooting10.2.4 Selecting the probable cause

19. Chapter 10 Monitor & Troubleshoot 10.2 Troubleshooting10.2.5 Implementing the solution • Common solutions: • replacing with a new hardware or • reconfiguring the server. • Note: • 1. If powering off is required, plan • the time to power off • making backup • 2. Implement solution with one fix at a time • otherwise, difficult to tell what has corrected the problem and why

20. Chapter 10 Monitor & Troubleshoot 10.2 Troubleshooting10.2.6 Testing the results • Testing • after implementing the solution • to verify that the solution really addressed the problem

21. Chapter 10 Monitor & Troubleshoot 10.2 Troubleshooting10.2.7 Documenting the solution • Documentation • provides a quick reference for future • include • what the problem was • how (and when) the solution was implemented • other solutions that have been tried out • who implemented the solution