COMPUTER NETWORKS
UNIT I:
Introduction: Network Types, LAN, MAN, WAN, Network Topologies
Reference models- The OSI Reference Model- the TCP/IP Reference Model - A
Comparison of the OSI and TCP/IP Reference Models, OSI Vs TCP/IP, Lack of OSI
models success, Internet History.
Physical Layer –Introduction to Guided Media- Twisted-pair cable, Coaxial cable and Fiber
optic cable and unguided media: Wireless-Radio waves, microwaves, infrared.
NETWORK: Network is a set of devices (often referred to as nodes) connected by
communication links. A node can be a computer, printer, or any other device capable of
sending and/or receiving data generated by other nodes on the network.“Computer
network’’ to mean a collection of autonomous computers interconnected by a single
technology. Two computers are said to be interconnected if they are able to exchange
information.The connection need not be via a copper wire; fiber optics, microwaves,
infrared, and communication satellites can also be used.
USES OF COMPUTER NETWORKS
1. Business Applications
to distribute information throughout the company (resource
sharing).
sharing physical resources such as printers, and tape backup systems, is
sharing information
client-server model. It is widely used and forms the basis of much network
usage.
communication medium among employees.email (electronic
mail), which employees generally use for a great deal of daily
communication.
Telephone calls between employees may be carried by the computer network
instead of by the phone company. This technology is called IP telephony or
Voice over IP (VoIP) when Internet technology is used.
Desktop sharing lets remote workers see and interact with a graphical
computer screen
doing business electronically, especially with customers and suppliers. This
new model is called e-commerce (electronic commerce) and it has
grown rapidly in recent years.
2.Home Applications
1
, peer-to-peer communication
person-to-person communication
electronic commerce
entertainment.(game playing,)
3.Mobile Users
Text messaging or texting
Smart phones,
GPS (Global Positioning System)
m-commerce
NFC (Near Field Communication)
4.Social Issues
With the good comes the bad, as this new-found freedom brings with it many
unsolved social, political, and ethical issues.
Network Definition – A group of computers which are connected to each other and follow
similar usage protocols for the purpose of sharing information and having communications
provided by the networking nodes is called a Computer Network.
A network may be small where it may include just one system or maybe as large as what one
may want. The nodes may further be classified into various types. These include:
1. Personal Computers
2. Servers
3. Networking Hardware
4. General Hosts
Networking can be classified into three types:
1. Types of Computer Networks
2. Topology
3. Interpreters
All are in detail further below
1.Types of Computer Networks
There are five main types of Computer Networks:
1.LAN (Local Area Network) –
Systems connected in a small network like in a building or a small office
It is inexpensive
It uses Ethernet or Token-ring technology
Two or more personal computers can be connected through wires or cables acting as
nodes
Transfer of data is fast and is highly score
2.PAN (Personal Area Network) –
2
, The smallest computer network
Devices may be connected through Bluetooth or other infra-red enables devices
It has a connectivity range of upto 10 metres
It covers an area of upto 30 feet
Personal devices belonging to a single person can be connected to each other using PAN
3.MAN (Metropolitan Area Network) –
A network that can be connected within a city, for example, cable TV Connection
It can be in the form of Ethernet, ATM, Token-ring and FDDI
It has a higher range
This type of network can be used to connect citizens with the various Organisations
4.WAN (Wide Area Network) –
A network which covers over a country or a larger range of people
Telephonic lines are also connected through WAN
Internet is the biggest WAN in the world
Mostly used by Government Organisations to manage data and information
5.VPN (Virtual Private Network): –
A network which is constructed by using public wires to connect to a private network
There are a number of systems which enable you to create networks using the Internet as
a medium for transporting data
These systems use encryptions and other security mechanisms to ensure only authorised
users can access
Topology:
Topology defines the structure of the network of how all the components are interconnected to
each other. There are two types of topology: physical and logical topology.
Physical topology is the geometric representation of all the nodes in a network.
Network Topologies
Given below are the eight types of Network Topologies:
1. Point to Point Topology – Point to Point topology is the simplest topology that connects
two nodes directly together with a common link.
2. Bus Topology – A bus topology is such that there is a single line to which all nodes are
connected and the nodes connect only to the bus
3. Mesh Topology – This type of topology contains at least two nodes with two or more
paths between them
4. Ring Topology – In this topology every node has exactly two branches connected to it.
The ring is broken and cannot work if one of the nodes on the ring fails
5. Star Topology – In this network topology, the peripheral nodes are connected to a
central node, which rebroadcasts all the transmissions received from any peripheral node
to all peripheral nodes on the network, including the originating node
3
, 6. Tree Topology – In this type of topology nodes are connected in the form of a tree. The
function of the central node in this topology may be distributed
7. Line Topology – in this topology all the nodes are connected in a straight line
8. Hybrid Topology – When two more types of topologies combine together, they form a
Hybrid topology
1.Bus Topology
1. The bus topology is designed in such a way that all the stations are connected through a
single cable known as a backbone cable.
2. Each node is either connected to the backbone cable by drop cable or directly connected
to the backbone cable.
3. When a node wants to send a message over the network, it puts a message over the
network. All the stations available in the network will receive the message whether it has
been addressed or not.
4. The bus topology is mainly used in 802.3 (ethernet) and 802.4 standard networks.
5. The configuration of a bus topology is quite simpler as compared to other topologies.
6. The backbone cable is considered as a "single lane" through which the message is
broadcast to all the stations.
Advantages of Bus topology:
1. Low-cost cable: In bus topology, nodes are directly connected to the cable without
4
UNIT I:
Introduction: Network Types, LAN, MAN, WAN, Network Topologies
Reference models- The OSI Reference Model- the TCP/IP Reference Model - A
Comparison of the OSI and TCP/IP Reference Models, OSI Vs TCP/IP, Lack of OSI
models success, Internet History.
Physical Layer –Introduction to Guided Media- Twisted-pair cable, Coaxial cable and Fiber
optic cable and unguided media: Wireless-Radio waves, microwaves, infrared.
NETWORK: Network is a set of devices (often referred to as nodes) connected by
communication links. A node can be a computer, printer, or any other device capable of
sending and/or receiving data generated by other nodes on the network.“Computer
network’’ to mean a collection of autonomous computers interconnected by a single
technology. Two computers are said to be interconnected if they are able to exchange
information.The connection need not be via a copper wire; fiber optics, microwaves,
infrared, and communication satellites can also be used.
USES OF COMPUTER NETWORKS
1. Business Applications
to distribute information throughout the company (resource
sharing).
sharing physical resources such as printers, and tape backup systems, is
sharing information
client-server model. It is widely used and forms the basis of much network
usage.
communication medium among employees.email (electronic
mail), which employees generally use for a great deal of daily
communication.
Telephone calls between employees may be carried by the computer network
instead of by the phone company. This technology is called IP telephony or
Voice over IP (VoIP) when Internet technology is used.
Desktop sharing lets remote workers see and interact with a graphical
computer screen
doing business electronically, especially with customers and suppliers. This
new model is called e-commerce (electronic commerce) and it has
grown rapidly in recent years.
2.Home Applications
1
, peer-to-peer communication
person-to-person communication
electronic commerce
entertainment.(game playing,)
3.Mobile Users
Text messaging or texting
Smart phones,
GPS (Global Positioning System)
m-commerce
NFC (Near Field Communication)
4.Social Issues
With the good comes the bad, as this new-found freedom brings with it many
unsolved social, political, and ethical issues.
Network Definition – A group of computers which are connected to each other and follow
similar usage protocols for the purpose of sharing information and having communications
provided by the networking nodes is called a Computer Network.
A network may be small where it may include just one system or maybe as large as what one
may want. The nodes may further be classified into various types. These include:
1. Personal Computers
2. Servers
3. Networking Hardware
4. General Hosts
Networking can be classified into three types:
1. Types of Computer Networks
2. Topology
3. Interpreters
All are in detail further below
1.Types of Computer Networks
There are five main types of Computer Networks:
1.LAN (Local Area Network) –
Systems connected in a small network like in a building or a small office
It is inexpensive
It uses Ethernet or Token-ring technology
Two or more personal computers can be connected through wires or cables acting as
nodes
Transfer of data is fast and is highly score
2.PAN (Personal Area Network) –
2
, The smallest computer network
Devices may be connected through Bluetooth or other infra-red enables devices
It has a connectivity range of upto 10 metres
It covers an area of upto 30 feet
Personal devices belonging to a single person can be connected to each other using PAN
3.MAN (Metropolitan Area Network) –
A network that can be connected within a city, for example, cable TV Connection
It can be in the form of Ethernet, ATM, Token-ring and FDDI
It has a higher range
This type of network can be used to connect citizens with the various Organisations
4.WAN (Wide Area Network) –
A network which covers over a country or a larger range of people
Telephonic lines are also connected through WAN
Internet is the biggest WAN in the world
Mostly used by Government Organisations to manage data and information
5.VPN (Virtual Private Network): –
A network which is constructed by using public wires to connect to a private network
There are a number of systems which enable you to create networks using the Internet as
a medium for transporting data
These systems use encryptions and other security mechanisms to ensure only authorised
users can access
Topology:
Topology defines the structure of the network of how all the components are interconnected to
each other. There are two types of topology: physical and logical topology.
Physical topology is the geometric representation of all the nodes in a network.
Network Topologies
Given below are the eight types of Network Topologies:
1. Point to Point Topology – Point to Point topology is the simplest topology that connects
two nodes directly together with a common link.
2. Bus Topology – A bus topology is such that there is a single line to which all nodes are
connected and the nodes connect only to the bus
3. Mesh Topology – This type of topology contains at least two nodes with two or more
paths between them
4. Ring Topology – In this topology every node has exactly two branches connected to it.
The ring is broken and cannot work if one of the nodes on the ring fails
5. Star Topology – In this network topology, the peripheral nodes are connected to a
central node, which rebroadcasts all the transmissions received from any peripheral node
to all peripheral nodes on the network, including the originating node
3
, 6. Tree Topology – In this type of topology nodes are connected in the form of a tree. The
function of the central node in this topology may be distributed
7. Line Topology – in this topology all the nodes are connected in a straight line
8. Hybrid Topology – When two more types of topologies combine together, they form a
Hybrid topology
1.Bus Topology
1. The bus topology is designed in such a way that all the stations are connected through a
single cable known as a backbone cable.
2. Each node is either connected to the backbone cable by drop cable or directly connected
to the backbone cable.
3. When a node wants to send a message over the network, it puts a message over the
network. All the stations available in the network will receive the message whether it has
been addressed or not.
4. The bus topology is mainly used in 802.3 (ethernet) and 802.4 standard networks.
5. The configuration of a bus topology is quite simpler as compared to other topologies.
6. The backbone cable is considered as a "single lane" through which the message is
broadcast to all the stations.
Advantages of Bus topology:
1. Low-cost cable: In bus topology, nodes are directly connected to the cable without
4
