MARCH/APRIL 2016 EXAMINATION
COURSE CODE: CIT 311
COURSE TITLE: COMPUTER NETWORKS
1. (i) What Is Networking? (5 marks)
Answer= A network is when more than two or more computers are connected by a cable or by a wireless connection so that they can communicate and exchange information or data.
(ii) Enumerate the Goal(S) Of Networking. (6 marks)
• To enable its users to share and access resources, regardless of their physical locations (Distance is removed as a barrier)
• Creates a global environment for its users and computers.
• provide communication services (such as E–mail) and in general, to provide robust transport network. i.e., (highway) over which application can be built.
(b) Briefly Explain And Indicate the Differences Between LAN, MAN and WAN. (9 marks)
LAN- A local area network, consists of a computer network at a single site (usually an individual office building). It is very useful in sharing resources, (data storage and printers) A LAN typically relies mostly on wired connections for increased speed and security with maximum span of 10km to provide local connectivity.
MAN- A metropolitan area network, consists of a computer network across an entire city, college campus. A MAN is larger than a LAN, which is limited to a single building or site. A MAN is often used to connect several LANs together to form a bigger network. It is specifically designed for a college campus, and with a span less than 50km
WAN- A wide area network, occupies a very large area, such as an entire country or the entire world. A WAN can contain multiple smaller networks, such as LANs or MANs. It has an unlimited span an example is the Internet
2. (a) (i) What Is Topology. (4 marks)
• Network topology is the arrangement of the various elements (links, nodes, etc.) of a computer network.
• Network topology refers to the physical or logical layout of a network
• Network Topology refers to layout of a network and how different nodes in a network are connected to each other and how they communicate.
(ii) Explain the Differences between a Star Topology and a Tree Topology. (6 marks)
TREE TOPOLOGY - in a tree all device are linked to a central hub that controls the traffic to the network. Not every device plugs directly into the central hub. Majority of devices connect to a secondary hub that in turn is connected to the central hub.
STAR TOPOLOGY - Each device has a dedicated Point–to–Point link only to a central controller, called a hub. All device are plugged directly to the central hub. Devices are not linked to each other; each device needs only one link and one I/O Port to connect it to any number of other devices.
(b) Enumerate And Explain The Various Types Of Network Available. (10 marks)
• Point–to–Point network
• Broadcast network.
Point–to–Point networks consist of many connections between individual pairs of machines. To go from the to the source destination, a packet on this type of network may have to first visit one or more intermediate machine routers. Until the output lines are free and then forwarded the packet is stored at each intermediate router. A point-to-point transmission with one sender and one receiver is called unicasting.
Broadcast networks have a single communication channel that is shared by all the machines on the network. Short messages, called packets is sent by any machine and received by all the other machines. An address field within the packet specifies for when it is proposed. Upon receiving a packet, a machine checks the address field. If the packet is intended for itself, it processes the packet; else it ignores it if for others. Some broadcast systems also support transmission to a subset of the machines, something known as multicasting
3. (a) Explain What the OSI model refer to. (4 marks)
The ISO – OSI (International Standard Organization–Open Systems Interconnection) Reference
Model deals with connecting open systems – that is, systems that are open for communication with other systems.
It was designed to allow the manufacture of different systems to interconnect equipment through standard interfaces. And also to allow software and hardware to integrate well and be portable on different systems.
(b) Enumerate And Explain The Various Layers in an OSI Model. (16 marks)
(a) Physical Layer
(b) Data Link Layer
(c) Network Layer
(d) Transport Layer
(e) Session Layer
(f) Presentation Layer
(g) Application Layer.
1. Physical Layer defines electrical and mechanical specifications of cables, connectors and signaling options that physically link two nodes on a network.
2. Data Link Layer provides the functional and procedural means to transfer data between network entities and to detect and possibly correct errors that may occur in the physical layer.
3. Network Layer ensures that each packet travels from its source to destination successfully and efficiently.
4. Transport Layer accept data from the Session Layer, split into smaller units then pass to the Network Layer and ensure the pieces all arrive correctly at the other end.
5. Session Layer controls the connections between computers. It establishes, manages and terminates the connections between the local and remote application. It also allows ordinary data transport as transport layer.
6. Presentation Layer is concerned with the syntax and semantics of the information transmitted.
7. Application Layer is the OSI layer closest to the end user, which means both the OSI application layer and the user interact directly with the software application.
4. (a) Briefly Explain the TCP Reference Model. (6 marks)
TCP/IP (Transmission Control Protocol and Internet Protocol). Protocols are set of rules which govern every communication over the internet. These protocols describe the movement of data between the host computers or internet. It offer simple naming and addressing schemes
(b) Using Tabular Form, Indicate the Differences between OSI Reference Model and TCP
Reference Model. (14 marks)
OSI Reference Model Model
First comes description of model and protocol comes next
It distinguishes between service, interface and protocol.
Protocol comes first and description of model later.
Does not clearly distinguish between service, interface and protocol
Both have Network Transport and
supports connectionless and connection oriented communication in network layer and only connection–oriented communication in transport layer (Co2 T. service is visual to the User) easily (No Transparency)
TCP/IP has only one mode in Network layer (connectionless) but supports both modes in Transport layer
Protocol in OSI Model are better hidden and can be replaced relatively
Protocols in TCP/IP are not hidden and thus, cannot be easily replaced.
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