COMPUTER NETWORKING
A computer network is a collection of interconnected computers and other
devices which are able to communicate with each other and share hardware
and software resources.
Advantages of networked computers over stand alone computers
1. Resource Sharing
2. Cost saving
3. Collaborative user interaction
4. Time saving
5. Increased storage
TRANSMISSION MEDIUM A transmission medium is a medium of data transfer over a network. It can be
wired or wireless.
Wireless Media
Electromagnetic waves are used for wireless communication over computer networks. Frequencies of
waves are measured in Hertz (Hz). As the frequencies of electromagnetic waves change, their properties
also change. Based on their frequencies, electromagnetic waves are categorized into various categories.
These categories are (in increasing order of frequencies): radio waves, microwaves, infrared radiation,
visible light, ultraviolet radiation, X-rays, and Gamma rays.
A. Radio Waves 1. Radio waves have a frequency range of 3 KHz to 3GHz.
2. Radio waves are used for communication over distances ranging from a few meters (in walkietalkies) upto covering an entire city.
3. These waves are easy to generate, can travel long distances and can penetrate buildings easily.
4. Widely used for communication, both indoors and outdoors. E.g.Cordless phones, AM and FM
radio broadcast, Garage door openers etc.
5. These waves are omni-directional, so the transmitting and receiving antennas need not be
aligned.
6. Relatively inexpensive than wired media.
7. It offers ease of communication over difficult terrain
8. The transmission can be interfered by motors or other electrical equipment
9. Permission from concerned authorities is required for use of radio wave transmission
10. Less secure mode of transmission
B. Micro Waves –
1. Micro waves have a frequency range of 300MHz (0.3 GHz) to 300 GHz.
2. Microwaves travel in straight lines and cannot penetrate any solid object.
3. Relatively inexpensive than wired media
4. The transmission is in straight lines so the transmitting and receiving antennas need to be
properly aligned ( line of sight transmission)
C. Infrared Waves
1. Infrared waves have a frequency range of 300 GHz to 400 THz.
2. Short range communication (approx. 5m)e.g., monitoring and control applications, Homeentertainment remote-control devices, Cordless mouse and Intrusion detectors .
3. Major drawback- they do not pass through solid objects.
4. It is a line of sight transmission
D. Bluetooth
1. Bluetooth technology uses radio waves in the frequency range of 2.402 GHz to 2.480 GHz.
2. Short range communication (approx. 10m) e.g..Baby monitors, door openers, and cell phones
3. Line of sight between communicating devices is not required. (Think Why?)
4. Bluetooth can connect upto eight devices simultaneously.
5. Slow data transfer rate (upto 1Mbps).
E. Satellite Link –
1. Range from intercity to intercontinental i.e. satellites cover large area of earth
2. Since communication over very long distances is possible, this becomes a commercially attractive
option.
3. This system is expensive
4. Requires legal permissions.
NETWORK DEVICES
NIC: an NIC (Network Interface Card) is a device that enables a computer to connect to
a network and communicate.
Hub: a Hub is an electronic device that connects several nodes to form a network and
redirects the received information to all the connected nodes in broadcast mode.
Switch :a Switch is an intelligent device that connects several nodes to form a network
and redirects the received information only to the intended node(s).
Repeater: A Repeater is a device that is used to regenerate a signal which is on its way
through a communication channel. A repeater regenerates the received signal
and re-transmits it to its destination
Gateway: Gateway is a device, which is used to connect different types of networks and
perform the necessary translation so that the connected networks can
communicate properly.
NETWORK TOPOLOGIES
A Topology is an arrangement of physical connections among nodes in a network.
Bus Topology:
In bus topology all the nodes are connected to a main cable called backbone. If any node has to send some
information to any other node, it sends the signal to the backbone.
1. It is easy to install.
2. It requires less cable length and hence it is cost effective.
3. Failure of a node does not affect the network.
4. In case of cable (backbone) or terminator fault, the entire network breaks
5. down.
6. Fault diagnosis is difficult.
7. At a time only one node can transmit data.
Star Topology:
In star topology each node is directly connected to a hub/switch
1. It is more efficient topology as compared to bus topology.
2. It is easy to install
3. It is easy to diagnose the fault in Star topology.
4. It is easy to expand depending on the specifications of central hub/switch
5. Failure of hub/switch leads to failure of entire network
6. It requires more cable length as compared to bus topology.
Tree Topology
Tree topology is a combination of bus and star topologies
1. It offers easy way of network expansion
2. Even if one network (star) fails, the other networks remain connected and working.
TYPES OF NETWORKS
IDENTIFICATION OF COMPUTERS AND USERS OVER A NETWORK
MAC (Media Access Control) address: A MAC (Media Access Control) address is a unique 12 digit (6
digits for manufacturer code and 6 digits for serial number) hexadecimal number assigned to each NIC.
MAC address of an NIC never changes.
. MM:MM:MM:SS:SS:SS i.e.00:A0:C9 : 14:C8:35
IP Address An IP (Internet Protocol) address is a unique 4 digit hexadecimal number assigned to each
node on a network. IP address settings of a node can be changed by the user
59.177.134.72 "dotted decimal number”
IP Address Vs MAC Address:
The IP address is assigned by the network administrator or the internet service provider
While
The MAC address is assigned by the manufacturer.
If a computer is transferred from one network to another, its IP address gets changed where as the MAC
address remains the same.
Domain Name is a name assigned to a server through Domain Name System (DNS). A domain name
usually has more than one part: top-level domain name or primary domain name and sub-domain name(s).
Domain Name Resolution is the process of getting corresponding IP address from
a domain name.
olved Questions:
Q1. What is MAC Address?
Ans : In computer networking, a Media Access Control address (MAC) is a unique identifier
assigned to most network adapters or network interface cards (NICs) by the manufacturer for
identification, and used in the Media Access Control protocol sub-layer.
Q2. Write two advantages of networks.
Ans: Advantages: i) Data or information can be shared among the users.
ii) Fast communication can be achieved.
Q3. Write two disadvantages of networks.
Ans : Disadvantages of networks:
i. Sophisticated Hardware and software technology is required.
ii. Expensive to install network.
Q4. What is communication channel? Name the basic types of communication channels available.
Ans: What is communication channel? Name the basic types of communication channels available.
Communication channels mean the connecting cables that link various workstations. There are
3 basic types of cables:
_ Twisted Pair cables
_ Coaxial cables
_ Fiber-optic cables
Q5. Define a network.
Ans: A computer network is a system in which computers are connected to share information and
resources.
Q6. What is IP address?
Ans A unique number consisting of 4 parts separated by dots, e.g. 165.113.245.2 Every machine that
is on the Internet has a unique IP number - if a machine does not have an IP number, it is not
really on the Internet.
Q7. What is domain name? How is it alternatively known?
Ans The unique name that identifies an Internet site. Domain Names always have 2 or more parts,
separated by dots. The part on the left is the most specific, and the part on the right is the most
general. E.g.: matisse.net
Q8. What are the various types of networks?
Ans : Network can be classified on the basis of their size, complexity and geographical spread. On the
basis of geographical spread it can be classified as Local Area Network, Metropolitan Area
Network and Wide Area Network.
Q9. What is the difference between MAN and WAN?
Ans : A metropolitan area network (MAN) is a large computer network that usually spans a city or
a large campus.
WAN is a network that covers an area larger than a single building or campus such as across
the cities or countries.
Q10. What is meant by Topology? Name some popular topologies.
Ans: Network topology is defined as the interconnection of the various elements (links, nodes, etc.)
of a computer network. In computer networking, topology refers to the layout of connected
devices.
• Bus topology
• Star topology
• Ring topology
• Tree topology
• Mesh topology
Q11. What are the similarities and differences between bus and tree topologies?
Ans: In bus topology each machine is connected to a single cable. Each computer or server is
connected to the single bus cable through some kind of connector.
Tree topology is a network with the shape of an inverted tree in which a single link between
two nodes.
Q12. What are the limitations of star topology?
Ans i) Central node dependency: In this topology central node is a controller of the network. If the
central node fails, the entire network will be failed.
ii) Difficult to expand: The addition of a new node to a network involves a connection all the
way to the central node.
Unsolved Questions:
1. What are the goals of network?
2. Write the applications of network?
3. What do you understand by domain name resolution?
4. What are communication channels? Discuss various channels available for networks?
5. Advantages and disadvantages of the followings :
i. optic fiber
ii. coaxial cables
iii. twisted pair cables
iv. radio waves
v. microwaves
vi. Satellites
6. Discuss and compare various types of networks?
7. Explain mostly used topologies.
8. What are hubs? What are its types?
9. What is the role of a switch in a network?
10. Discuss repeater.
11. What are common threats to network security?
12. What are denial of services attacks?
13. How can you prevent/ counter threats of network security?
14. When do you think, ring topology becomes the best choice for a network?
15. Write the two advantages and two disadvantages of star topology in network.
16. Write the disadvantages if twisted pair cables.
17. Define Hub.
18. Define switch.
1. What is MAC Address?
2. Write two advantages of networks.
3. Write two disadvantages of networks.
4. What is communication channel? Name the basic types of communication channels available.
5. What is IP address?
6. What is domain name? How is it alternatively known?
7. What are the various types of networks?
8. What is the difference between MAN and WAN?
9. What is meant by Topology? Name some popular topologies.
10. Define a network
11. What are the similarities and differences between bus and tree topologies?
12. What are the limitations of star topology?
13. What are the goals of network?
14. Write the applications of network?
15. What do you understand by domain name resolution?
16. What are communication channels? Discuss various channels available for networks?
17. Advantages and disadvantages of the followings :
i. optic fiber
ii. coaxial cables
iii. twisted pair cables
iv. radio waves
v. microwaves
vi. Satellites
18. Discuss and compare various types of networks?
19. Explain mostly used topologies.
20. What are hubs? What are its types?
21. What is the role of a switch in a network?
22. Discuss repeater.
23. What are common threats to network security?
24. What are denial of services attacks?
25. How can you prevent/ counter threats of network security?
26. When do you think, ring topology becomes the best choice for a network?
27. Write the two advantages and two disadvantages of star topology in network.
28. Write the disadvantages if twisted pair cables.
29. Define Hub.
30. Define switch