HW 3b

1. Page 285: 4, 7
2. Page 287: 25, 27, 28, 29, 30, 32
3. SYN flood:
   1. Describe how the SYN flood attack works.
   2. Suppose that a server allocates 10KB to each connection. Furthermore, suppose that the server retransmits the SYN-ACK after 2^(n-1)*3 seconds where n is the number of times the SYN-ACK has been sent and gives up after retransmitting the same SYN-ACK 6 times. What bandwidth must the attacker use in order to cause a server to allocate 1GB.
4. Anonymous scanning: Use a sequence of diagrams to show how TCP-SYN with a spoofed source address and IP fragment ID is used to scan anonymously. Would this technique still work if IP fragment ID are not sequential, but random?
5. Describe how sending an ACK for each byte (as oppose to each packet) will cause the server to flood the network.
6. Bit-rate
   1. How long does it take to complete a file transmission of a file that fits into one packet?
   2. If the maximum size of the receiver window is 120KB, what is the maximum bit-rate a connection can achieve?
   3. Assume that a connection crosses three links and that only one connection is using these links. The first and last links are 100Mbps links while the middle link is a 1Mbps link. Assume there is no queue, so as soon as the sending rate exceeds 12KB, a packet is dropped. What is the average bit-rate during AIMD?