Question1 – Computer Network Topologies, Network Devices [14 marks]
a) List four common LAN topologies and briefly describe their methods of operation by using appropriate diagrams and text. Discuss how the nodes are connected, the transfer of data and its advantages and disadvantages.
(6 marks)

b) Star topology is to be provided that spans two buildings. Each building will have an independent star topology network and a point-to-point link will connect a special communications station on one network with a communications station on the other network.
i. Explain the functions that the communications stations must perform?
ii. At which layer would the communication stations operate in?
(3 marks)

c) Describe the difference between a bridge and a router. Where would you use each of these network devices, describe the scenarios where you would use each of them
(5 marks)

Question 2 – Layered network Architecture, Reference Models [10 marks]
a) Explain why layering is important in computer networking
(3 marks)

The above figure shows two Ethernet LANs connected by R1. Suppose an application software running at Host A with port address 120 is sending a message to a peer application software running at host B with port 150.Using relevant diagrams and text, show the packets at each layer and only the ‘address’ related contents of the segment, datagram, and frames at the transport, network and data link layer for each hop. [Hint: there are 2 hops]
(7 marks)
Question 3 – LAN, WAN Technologies [11 marks]
a) A common method for providing broadband Internet access over existing telephone lines is Asymmetric Digital Subscriber Line (ADSL).
i. Why is it called asymmetric?
(2 marks)

ii. What are other types of DSL technologies available, name at least 4 types
(2 marks)

b) Briefly describe how ADSL is able to transmit both data and telephone calls over the same twisted pair cable connecting a house to a local exchange, without the two signals interfering with each other.
(2 marks)

c) Why would users select satellite for internet when it is expensive?
(2 marks
d) A satellite link has about 500 milliseconds return trip latency? Will this be suitable for voice calls? Why?
(3 marks)

Question 4 – IP addresses and Routing [20 marks]
a) A user turns on the computer on and connects to the organisation’s network. The user then selects a link to www.google.com.
i. Describe the process of how the user is granted an IP address to access the internet.
(3 marks)

b) Explain the difference between DHCP and DNS including, why and when they are requested.
(5 marks)

c) Explain the steps in sequence of how the application layer to network layer resolution takes place in relation to above website link request. Assume the network layer address is provided by the TLD name server.
(5 marks)

d) Suppose you are managing the network at a firm that has two hundred end users in a large office block, working for a financial trading company with fast-changing financial data. You have just submitted a request to purchase a router. Your boss asks you to explain to him why you’re requesting to buy routers that uses link state dynamic routing at $1000 when you can buy a cheaper one using distance vector dynamic routing at $600.
i. Explain the reasons for your recommendations.
(7 marks)