1(a)(i) CSMA/CD- A set of rules determining how network devices react when two or more devices attempt to use data channel at the same time which is called a collision. Once collision is detected transmission is then aborted reducing the channel wastage considerably. OSI Layer: Data Link Layer. Function of Data Link layer: Data are sent in blocks called frames. The start and end of each frame must be recognized. Any bit error initiated by the transmission system must be detected and corrected. The layer regulates the flow of data so that the sender must not send frames at rate faster than the receiver can absorb them. (ii) Repeater- It is used to amplify signals carried by a network. The repeater receives incoming signals or a packet of data. It retransmits them at a higher level so that the signal can cover a longer distance. OSI Layer: Physical Layer. Function of Physical layer: The physical layer transports a bit stream from one computer to another. It performs establishment and termination of a connection to a communications medium. It modulates the representation of digital data in user equipment and the corresponding signals transmitted over a communications channel.
(iii) TCP: A connection-oriented transport protocol that provides reliable end-to-end byte stream over an unreliable internet. It can perform error control and retransmission. There is handshaking, an exchange of control messages between the sender and the receiver before data exchange. TCP performs bi-directional data flow control in same connection. It is used in HTTP, FTP and TELNET. OSI Layer: Transport Layer.