University of Texas at Dallas Computer Science Program

UTD-CS 6390.001 Advanced Computer Networks-Spring 2004-Exam I

Name:______

Notes: There are questions on both pages. Answer all questions.

1. (13 points) Consider the following example of hosts and learning bridges (see figure) starting from scratch. Show the forwarding table entries of each bridge after each of the following activities occurring in the given sequence: (Note that there is sufficient time between two packets sent. Also, assume that a MAC layer ack is sent for each packet sent.)

A to B

C to E

C to D

2. (12 points) Explain the 4-way handshake for SCTP association establishment. In particular, show all the important aspects of SCTP and the important differences between SCTP and TCP. Also, show how a chunk is sent to the destination and all the important related events. 3. (10 points) Explain why RTP rides on top of UDP and not TCP. What are the four most important fields carried in the RTP header? Explain the need for each of the four important fields. 4. (10 points) Assume that RSVP is used for implementing QoS. There are 20 routers between the source host and the destination host. Each packet takes d mS to go on a hop after it is scheduled to be transmitted. (This is the transmission time between the sender’s and receiver’s port.). There are three input ports and three output ports at each router. The average number of packets in each input port is n and the average number of packet at each output port is n. The lookup time per packet with RSVP enabled is 0.2 microsecnd and 0.1 without RSVP enabled. Assume that there is only one RSVP path set up. What value of d for which it is preferable to use RSVP for this scenario? 5. (10 points) What methods are needed to route packets that are IPv4 and IPv6 with some routers that have IPv6 built-in while the other routers are legacy routers that deal with IPv4 only? Sketch the architecture of your network and the important design decisions you make.

6. (10 points) If reliable multicasting is to be implemented at the network layer, what changes are needed to the routers? What techniques will you use? 7. (10 points) What is the main idea behind fair queueing and weighted fair queueing. Explain with an example.