1. Consider the following subnet in which the routers are labeled A through F. Distance vector routing is used, and D's routing table initially contains only information about reaching C and F (its nearest neighbors). In other words, D has not received any update messages yet.

Suppose the following vectors have just come into router D: From C: (13, 4, 0, 6, 6, 14) From F: (10, 12, 16, 14, 2, 0) The measured delays to C and F are 4 and 97 respectively.

What is C's new routing table? Give both the outgoing line and the expected delay.

Dest. Outgoing Line Delay A B C E F

2. What is the fastest line speed at which a host can blast out 1500-byte TCP payloads with a 120- sec maximum packet lifetime without having the sequence numbers wrap around?

Take TCP, IP, and Ethernet overhead into consideration. Assume that Ethernet frames may be sent continuously.

3. Consider the network shown: Assume that the weight on the lines is the currently known link delay. Run Dijkstra's algorithm to find the shortest paths from source node A to all other nodes in the network.

Show all your work (show the intermediate tables you generate)

4. Consider the network shown in the previous problem. Run the non-distributed Bellman-Ford algorithm to find the shortest paths from source node A to all other nodes in the network.

Show all your work (show the intermediate tables you generate)

5. Given a router with 4 interfaces/links which are labeled 0 - 3, and a forwarding table as follows:

IP Prefix Output Link 192.168.0/17 0 192.168.32/19 1 192.168.64/18 2 192.168.127/24 3 192.168.128/18 0 192.168.160/19 1 192.168.186/24 2 192.168.191/24 3 192.168.192/18 0 What interface will a packet with a destination IP address of 192.168.96.75 be sent out on?

6. Suppose Host A sends three TCP segments back to back to Host B over a TCP connection. The first segment has sequence number 120. The second segment has sequence number 121. The third segment has a sequence number of 1145. How much data is in the first segment? How much data is in the second segment? How do you know?

7. Consider the Go Back N protocol with 8 bit sequence numbers (i.e., a sequence number space of size 256). What is the largest allowable sender window that will avoid the occurrence of the problem where a new packet is indistinguishable from a retransmission?

8. Consider the Selective Repeat protocol with 8 bit sequence numbers (i.e., a sequence number space of size 256). What is the largest allowable sender window that will avoid the occurrence of the problem where a new packet is indistinguishable from a retransmission?

9. Consider the effect of using slow start on a line with a 10-msec round-trip time and no congestion. The receive window is 24 KB and the maximum segment size is 2 KB. How long does it take before the first full window can be sent?

10. Suppose datagrams are limited to 1500 bytes (including the header) between source and destination. Assuming a 20 byte IP header (with no options present), how many datagrams would be required to transfer a video file consisting of 500,000,000,200 bytes.

11. Suppose a UDP segment contains the following data: 00001001 01101001 00100011 01111100 00000000 00010100 00000000 00000000 11110000 11110000 00001111 00001111 10101010 01010101 01010101 10101010 11111111 00000000 11001100 00110011

Suppose a segment checksum needs to be computed for this segment.

What is the checksum value that is computed? Where is this checksum placed in the segment? Assuming there are no errors during transmission of the segment, what do you expect the verification step to produce as a result when verifying the checksum on the receiver?

12. Suppose two packets arrive to two different input ports of a router at exactly the same time. Also, suppose there are no other packets anywhere in the router. If the packets are to be forwarded to two different output ports, is it possible to forward the packets through the switch fabric at the same time when the fabric uses a shared bus? Is it possible to forward the packets through the switch fabric at the same time when the fabric uses a crossbar? Explain.