1. 1 Internet Management and Security We will look at management and security of networks and systems. Systems: The end nodes of the Internet Network: The nodes providing connectivity in the Internet Resources: End nodes, nodes and links In this way we cover all the Internet nodes!

2. 2 What will you get out of it? Maybe a job as: –A network manager or systems manager. –A consultant evaluating other people’s networks and systems. –A capacity planning analyst for an ISP. –A network security analyst. –A spy.

3. 3 Course Outline Introduction System Performance Internet Traffic Network Management Cryptography System Security Network Security

4. 4 System performance Client-Server architecture –Types of clients –Types of servers –Scalability Performance parameters –Availability/Reliability –Error rate –Response time/Delay –Throughput/Goodput –Resource utilisation

5. 5 Client-Server architecture Basic definition: –A client or customer requires a service, the server provides it. Examples: –Like queueing at the bank and waiting to be served by a cashier –Like requesting a web page to read my e-mail –Like having many programs open in windows and each one waiting to be served by the processor

6. 6 Client-Server architecture Client PC Server Network Service Clients Receive Services Servers Provide Services Usually, Two Types of Stations Clients and Servers Request

7. 7 Clients Client is the equipment requesting the service. Examples of clients are: –PCs (desktops and laptops) –PDAs (Personal Digital Assistants) –MP3 players –Cellular phones

8. 8 Servers Servers are the equipment providing the service Examples of servers are: –Web servers (like yahoo, gmail, etc.) –Application servers –Data servers –Proxy servers

9. 9 Servers Depending on the service they provide and the demand for the service, servers can have take different forms: –PCs –Clusters of PCs –Workstations –Mainframes and super computers –Computer grids

10. 10 Scalability Definition: Scalability is the ability of a resource (system or network) to meet requests as demand grows. Usually we refer to scalability when we try to answer the question: How long before I have to buy a bigger system/router?

11. 11 Scalability Very important when buying new equipment The relationship between scalability and cost usually determines the new purchases of equipment Buying new equipment is in most cases more expensive than upgrading the existing one Replacing equipment means an interruption in service to users

12. 12 Performance parameters – Availability/Reliability Ratio of average uptime to average downtime. system is up and running system is down Define: MTBF: Mean time between failures MTTR: Mean time between repaires Availability(%)=

13. 13 Performance parameters – Error Rate Bit Error Rate (BER) vs Packet Loss Ratio (PLR) Typical BER for is 10 -6 for voice links PLR depends on packet length, bit error distribution, and presence of error correction BER= PLR=

14. 14 Performance parameters – Response time/delay Is the time elapsed from the beginning to the end of the transaction The response time has several components: –Processing delay –Propagation delay –Transmission delay –Queueing delay Measured in mean values (seconds)

15. 15 Performance parameters – Throughput/Goodput Actual information received (good information) measured in bits per second Reduced by protocol headers and re- transmissions Throughput=

16. 16 Performance parameters – Resource utilisation Ratio of used resources to available resources Transmission capacity CPU Buffer space

17. 17 Summary By now you should understand: Why Internet management and security is important The relevance of the client-server architecture and how it can be achieved The main performance parameters, how to obtain them and what is their use in Internet management

18. 18 Next week… Internet traffic –Traffic measurement techniques –Weekly traffic patterns –Daily traffic patterns –Internet path traffic patterns