Question 1 Transport Layer

a) The Internet layer of TCP/IP has two protocols – IPv4 and IPv6. The transport layer provides two main protocols TCP and UDP (along with some special-purpose, minor protocols). But these are for very different reasons. Why are the Internet and Transport layers very different in providing two protocols?

b) Since UDP does very little that is different from IP, why do we even have a transport layer such as UDP?

c) Describe how DDoS attacks may be mounted against TCP and UDP services. In what way will being connection oriented be different for TCP and UDP?

Question 2 – IP Addressing

a) Perform the following boolean operations on the given bit patterns

i. not 11100010

ii. 11100010 or 00001110

iii. 11100010 and 00001110

b) What are the subnet masks for the following slash address blocks?

i. /9

ii. /17

iii. /31

c) Are the following address masks legal? If so, what are their slash forms? If not, why are they not legal?

i. 255.255.248.0

ii. 255.224.252.0

iii. 255.255.255.224

iv. 255.255.156.0

d) How many computers are in networks with the following address blocks?

i. /13

ii. /26

e) A small company is assigned the class C network 205.67.35.0. You need to divide this network to provide subnets for three departments using fixed-length subnetting. The departments are approximately the same size. Show the network and broadcast addresses for each subnet. Show the slash notation. How many hosts are on each subnet? Are the resulting subnets class C networks?

Question 3 – Wireless

a) Explain why CSMA/CD scheme used in traditional Ethernet LANs cannot be used in 802.11 wireless LANs.

b) A supermarket uses WiFi to enable staff to check inventory levels and to perform price checks. Staff have complained that the wireless scanners they use to check stock levels do not work reliably in some isles. The supermarket manager has contracted you to diagnose the wireless problems and correct them. The supermarket is 60m by 40m. Assume that the useful range of WiFi within the warehouse will be 15m radius. The access points are organised into a grid with the following channel allocations:

i. You have determined that the channel allocations are not optimal, how would you improve upon the current channel allocations?

ii. As you are reconfiguring the access points you notice that none of them currently have any security enabled. Is this a problem, and if so, what type of security would you recommend?