Short Answer Problems
- (25.4) The largest IP packet is 65535 octets. The smallest IP header is 20 octets. The smallest UDP header is 8 octets. So the theoretical largest possible UDP message is 65507 octets.
- (26.4) The major problems are (1) Unreliable communication: Packet loss, corruption, duplication, delay, out-of=order arrival; (2) End System Reboot; (3) Heterogeneous End Systems (some fast, some slow); and (4) Congestion.
- (26.6) If the window size is N packets, then N packets can be sent without waiting for an ACK.
- (26.12) TCP computes a timeout as a a linear combination of the estimated mean and estimated variance of round-trip delay estimates.
- (26.15) Chances of this happening are infinitesimal, see https://networkengineering.stackexchange.com/q/58907
- (27.2) There should be at least one entry for deliver-direct and an entry for the default route.
- (30.8) The eight basic security techniques mentioned in the book are:
- Hashing, for Data integrity
- Encryption, for Privacy
- Digital Signatures, for Message authentication
- Digital Certificates, for Sender authentication
- Firewalls, for Site integrity
- Intrusion Detection Systems, for Site integrity
- Deep Packet Inspection & Content Scanning, for Site integrity
- Virtual Private Networks (VPNs), for Data privacy
- (30.11) This feels like a trick question because you should never use DES. Its maximum key length of 56 bits is too small. If you were stuck with having to use it, you should, I guess, use the full 56-bit key size. But don’t use DES: it has many successors with longer keys.
- (30.14) One party first signs with their private key, then the second party signs with its private key.
- (30.17) You should deny by default and explicitly say which packets you will accept. You can always add more later. If you did accept by default and only listed the packets you want to deny, you might not get all of them: nasty packets get through, and the damage has been done.
- (30.21) I think (20 + 1486) × K.