Networking

1. Networking • A few questions on the course • A few questions about the course

2. 43 of 70 The Director of Studies is • Alwyn Barry • James Davenport • Alan Hayes • Mickey Mouse

3. That was the “warmup” • I hope you got Alan Hayes: • James Davenport is so last year! • Alwyn Barry is just history • (as far as this job is concerned!)

4. Questions on the course (mostly factual, but there is more to the course than facts)

5. An Ethernet address is how long? • 4 bytes • 6 bytes • 16 bytes • Variable length

6. The answer is B (6 bytes) If you didn’t get that, you’re pretty confused: re-read sections 2.2 and 3.2 of the book.

7. 100 Mbps twisted pair length limit is • 60 metres • 100 metres • 195 metres • 500 metres

8. The correct answer is B: 100m However, this is the sort of factual answer: • I don’t expect you to know, and would give you in an exam question; • You should always check in real life, especially if equipment installation depends on it; • As I showed in the Library, isn’t what it seems in practice

9. Internet and Ethernet • An internet is impossible without Ethernet • The Internet needs Ethernet • Today’s Internet depends on Ethernet • Totally independent concepts

10. I hope that made you think • Certainly false • Was false in the beginning, and may well be false again. • True in practice today. • True, but not as helpful as C.

11. When it comes to END characters, PPP • Is better than SLIP, as it doesn’t use one • Has one, which can’t be used in IP • Allows it in the middle of IP packets • Allows it anywhere in IP packets

12. The correct answer is D:anywhere in IP packets • Since PPP doesn’t have a length field, it must have some END marker • IP can contain arbitrary binary data, so B and C can’t be right. • If there is an END character in the IP packet, it is “escaped” by the sending PPP, and re-interpreted by the receiver • See figure 2.2

13. When it comes to delivering packets, IP • Guarantees to deliver • Guarantees to deliver or return an ICMP error • Makes no guarantees

14. The answer is C • On Ethernets, you have no idea if the packet is received • Congested routers may just drop packets • No error is generated for header checksum errors • No error is generated for broadcast or multicast packets • Etc.

15. The system administrator decides on the routing mechanism • True • False

16. False • There is only one routing mechanism: see Stevens sections 9.1, 9.2. • Who confused routing mechanism with policy?

17. The manager of an autonomous system in the Internet • Can do whatever he likes • Must implement the routing policy of whoever his AS is connected to • Must satisfy the constraints of whoever his AS is connected to • Depends on whether it’s stub/transit

18. True, but he may not stay connected to the Internet for very long. • It would be rare to be told what routing policy to implement. • Yes, such constraints must be satisfied. • In theory no, but in practice a transit AS will have many more constraints.

19. Networking • A few questions on the course • A few questions about the course

20. The textbook is a fantastic resource • Strongly Agree • Agree • Neutral • Disagree • Strongly Disagree

21. Actually, I use other sources • Strongly Agree • Agree • Neutral • Disagree • Strongly Disagree

22. My principal other source is • Bradford’s book • Farouzan’s book • Other book • Wikipedia • Other on-line non-book sources • A mixture • No other source

23. If you had “other” • Then you can tell us. • Text to 07624804921.

24. The lecturer uses the textbook far too much in lectures • Strongly Agree • Agree • Neutral • Disagree • Strongly Disagree

25. What about this technology • Revolutionises problem classes • Useful extra, but shouldn’t dominate • OK 1-2 times/term • Never again • Abstain