Apr 1999 AN215: Advanced Networking (Question 1)

(a)	Describe, using a diagram, the three phases of activity involved in circuit switching.	[4]
	Circuit switching require a dedicated path between two station to be established before it start transmission of data. Three activities require are call set-up, data transfer and call termination. Call setup - Station A require to dial up to station to established a connection. Data transfer - When the connection is established, station A can start the data transmission. Call termination - When the transmission is completed. Both Station A and B will release the connection and free the path. It can be sued by other party or station.
(b)	A router may be used to overcome several differences between different types of network. At which layer in the OSI or TCP/IP model does a router operate? Describe two differences between networks that a router may be used to overcome.	[5]
	Router operate at the Network Layer of the OSI or TCP/IP model. Router is used to interconnect two or more desimilar network together. - Ability to handle addressing issue where it has the intelligence to route to different network based on the given address. - Segmentation issue when some network has different packet size and router can packetize the size to be received by the receiver network correctly.
(c)	What features of electronic mail make it particularly suitable for transmission by message switching?	[3]
	The nature of electronic mail which is a one way transmission and it's relatively small and does not require a real time interaction make it suitable for transmission by message switching.
(d)	TCP and UDP are both transport layer protocols that are used in the Internet. How are they different?	[2]
	TCP is a connection oriented protocol while UDP is a connectionless oriented type of protocol.
(e)	List two types of network topologies that are very susceptible to the problem of a single point of failure? Explain your answer.	[2]
	Star topologies and Ring topologies are two types of network topologies that are very susceptible to the problem of a single point of failure. Star Topology where there is a central controller hub that connect to all node in a radial or star manner. The central control hub manage and control all the transmission of the connected node and all transmission need to pass through the central hub. If the central hub fails,the whole network will be effected. Ring Topology where all nodes are connected to a unidirectional transmission medium in a closed loop manner. Any failure to any node will cause the whole network to fail.
(f)	A repeater is a device sometimes found in long-distance communications systems. Which layer do repeaters operate at? Explain what this device is and why it is employed in data communications.	[4]
	Repeater operate at the physical layer of the OSI model. A repeater is used to amplify the signal in the transmission. On data communications If the physical distance between node or station is too far, a repeater is employed to boost up the signal at a regular distance to prevent signal loss or 'weak' signal at the receiving end.