CMPE 257 Homeworks

Assignment 1 Due date: 04.24.2003

1. Explain the purpose of MACAW's DS frame? Describe a mechanism to replace it. Explain the trade-offs between the two approaches.

2. Comment on MACAW's RTS-CTS-DATA-ACK exchange as compared to MACA's RTS-CTS-DATA in light of the End-To-End argument (Saltzer J., Reed D. and Clark D., "End-to-end Arguments in System Design.", ACM Transactions on Computer Systems (TOCS), Vol. 2, No. 4, pp. 195-206, 1984)

3. How does MACAW try to solve the unfairness of 802.11's exponential backoff mechanism? Does this technique work in any network topology?

4. What kind of multiple access technique is used by DVCS? How does it accommodate node heterogeneity?

5. Hidden terminals cause collisions at the receiver station. What kind of performance degradation is caused by exposed terminals? Explain

HW1 Solutions

Assignment 2 Due date: 05.09.2003

Mobile IP

1. Could Mobile IP be replaced by DHCP?

2. Discuss the systemic issues related to HA and FA functionality placement (at router versus dedicated server).

3. Would you classify Mobile IP's mobility management as a hard- or soft-state mechanism? Explain.

Unicast Routing

1. Based on the paper by Broc et al. "A Performance Comparison of Multi-Hop Wireless Ad-Hoc Network Routing Protocols" from the reading list, provide sample (qualitative) scenarios in which DSR performs better than AODV and scenarios in which AODV is the best performer. Discuss the reliability versus overhead trade-off. Explain your answer.

2. Draw an optimal and a worse-case topology for OLSR. Explain.

3. Discuss the trade-offs in determining ZRP's Routing Zone radius.

HW2 Solutions

Assignment 3 Due date: 05.23.2003

Multicast Routing:

1.The
CAMP comparison paper mentions that ODMRP does not  scale well
with  number of senders. Why ? Suggest means to improve the
scalability of ODMRP.   How would you modify ODMRPs timers to
adapt to mobility?

      

      2. In class we reviewed DSR which is a unicast protocol
based on source routing. Explain how DSR can be modified to support
multicasting ?

      

Transport Layer:

1. In class, we described Snoop TCP for scenarios where the TCP sender is in the wired network and the TCP receiver behind the wireless link. Explain the problems that can arise with the described Snoop approach in the case the TCP sender is the mobile host. What changes do you suggest to fix these problems? Explain.

2. Why may I-TCP violate application correctness? Does Snoop incur the same problem? Explain.

3. Give an example scenario where neither Snoop TCP nor I-TCP can be used. Explain. What kind of approach would you use in this scenario? Explain.

4. Discuss the advantages and disadvantages of explicit notification- versus pure end-to-end approaches to improve the performance of TCP in wireless networks.

5. Comment on the impact of route caching on the performance of TCP in MANETs.

6. Given what we discussed in class about achieving reliable multicast in wireless- (in particular ad hoc) versus wired networks, describe how you would design a MANET reliable multicast protocol targeting streaming media services. Comment on the approach you would use for feedback control, retransmission, congestion control, etc. and explain your design choices.

	Assignment 1 Due date: 04.24.2003 1. Explain the purpose of MACAW's DS frame? Describe a mechanism to replace it. Explain the trade-offs between the two approaches. 2. Comment on MACAW's RTS-CTS-DATA-ACK exchange as compared to MACA's RTS-CTS-DATA in light of the End-To-End argument (Saltzer J., Reed D. and Clark D., "End-to-end Arguments in System Design.", ACM Transactions on Computer Systems (TOCS), Vol. 2, No. 4, pp. 195-206, 1984) 3. How does MACAW try to solve the unfairness of 802.11's exponential backoff mechanism? Does this technique work in any network topology? 4. What kind of multiple access technique is used by DVCS? How does it accommodate node heterogeneity? 5. Hidden terminals cause collisions at the receiver station. What kind of performance degradation is caused by exposed terminals? Explain HW1 Solutions
	Assignment 2 Due date: 05.09.2003 Mobile IP 1. Could Mobile IP be replaced by DHCP? 2. Discuss the systemic issues related to HA and FA functionality placement (at router versus dedicated server). 3. Would you classify Mobile IP's mobility management as a hard- or soft-state mechanism? Explain. Unicast Routing 1. Based on the paper by Broc et al. "A Performance Comparison of Multi-Hop Wireless Ad-Hoc Network Routing Protocols" from the reading list, provide sample (qualitative) scenarios in which DSR performs better than AODV and scenarios in which AODV is the best performer. Discuss the reliability versus overhead trade-off. Explain your answer. 2. Draw an optimal and a worse-case topology for OLSR. Explain. 3. Discuss the trade-offs in determining ZRP's Routing Zone radius. HW2 Solutions
	Assignment 3 Due date: 05.23.2003 Multicast Routing: 1.The CAMP comparison paper mentions that ODMRP does not scale well with number of senders. Why ? Suggest means to improve the scalability of ODMRP. How would you modify ODMRPs timers to adapt to mobility? 2. In class we reviewed DSR which is a unicast protocol based on source routing. Explain how DSR can be modified to support multicasting ? Transport Layer: 1. In class, we described Snoop TCP for scenarios where the TCP sender is in the wired network and the TCP receiver behind the wireless link. Explain the problems that can arise with the described Snoop approach in the case the TCP sender is the mobile host. What changes do you suggest to fix these problems? Explain. 2. Why may I-TCP violate application correctness? Does Snoop incur the same problem? Explain. 3. Give an example scenario where neither Snoop TCP nor I-TCP can be used. Explain. What kind of approach would you use in this scenario? Explain. 4. Discuss the advantages and disadvantages of explicit notification- versus pure end-to-end approaches to improve the performance of TCP in wireless networks. 5. Comment on the impact of route caching on the performance of TCP in MANETs. 6. Given what we discussed in class about achieving reliable multicast in wireless- (in particular ad hoc) versus wired networks, describe how you would design a MANET reliable multicast protocol targeting streaming media services. Comment on the approach you would use for feedback control, retransmission, congestion control, etc. and explain your design choices.