A computer network is defined as the
interconnection of 2 or more independent computers
Need of Networks
– Communicate and collaborate
– Share information
– Share resources
– Sharing computer files and disk space
– Sharing high-quality printers
– Access to common fax machines
– Access to common modems
– Multiple access to the Internet
Classification of Networks
– Local Area Networks (LANs) - a computer
network covering a small geographic area, like
a home, office, or group of buildings. Typically
within 5-mile radius.
– Metropolitan Area Networks (MANs)- are
large computer networks usually spanning a
city. (within 30 miles)
– Wide-Area Networks (WANs) - any network
whose communications links cross
metropolitan, regional, or national boundaries.
The way in which the computers are
interconnected together is known as
Types of topologies
• Physical topology
• Logical topology
Types of physical topologies
Linear or bus topology
• Consists of a main cable, known as
backbone cable, with a terminator at
each end .
• All nodes (file server, workstations,
and peripherals) are connected to the
• Ethernet and LocalTalk networks use
Advantages of Bus Topology
• Easy to connect a computer or peripheral
to a linear bus.
• Requires less cable length.
• Easy to extend.
• If one node of the N/W is faulty, the N/W
can still remain working.
Disadvantages of Bus
• Entire network shuts down if there is a
break in the main cable.
• Terminators are required at both ends of
the backbone cable.
• Difficult to identify the problem if the entire
network shuts down.
• Not meant to be used as a stand-alone
solution in a large building.
• A star topology is designed with each node (file
server, workstations, and peripherals) connected
directly to a central network hub.
• Data on a star network passes through the hub
before continuing to its destination.
• The hub manages and controls all functions of
• It also acts as a repeater for the data flow.
Advantages of Star
• Easy to install.
• No disruptions to the network other than
connecting or removing devices.
• Easy to detect faults and to remove parts.
Disadvantages of Star
• Requires more cable length than a bus
• If the hub fails, nodes attached are
• More expensive than bus topology
because of the cost of the hub.
• A tree topology combines characteristics
of bus and star topologies.
• It consists of groups of star-configured
workstations connected to a bus
• Tree topologies allow for the expansion of
an existing network.
Advantages of a Tree
• Point-to-point wiring for individual
• Supported by several hardware and
Disadvantages of Tree
• Overall length of each segment is limited
by the type of cabling used.
• If the backbone line breaks, the entire
segment goes down.
• More difficult to configure than other
• Is a type of computer network configuration
where each network computer and device are
connect to each other forming A large circle.
• Data is divided into packets when transmitted.
• Packet is sent around the ring until it reaches
its final destination.
Advantages of ring
• Requires lesser amount of cable and there are
not much of installation problems
• All stations have equal access
Disadvantages of ring
• Failure of one computer may impact others
• Data transfer is slow
• It requires that every terminal should be
attached to each other.
• All the computers must have adequate
number of interfaces for the connections
to be made.
• Because of this requirement the
installations is somewhat difficult.
• The length of cable required is quite
higher as compared to other topologies.
Advantages of mesh
• Ease of troubleshooting.
• Data transfer is faster.
Disadvantages of mesh
• uses a lot of cabling.
• Most expensive topology
Choosing a Topology
• Money. A linear bus network may be the least
expensive way to install a network; you do not
have to purchase concentrators.
• Length of cable needed. The linear bus
network uses shorter lengths of cable.
• Future growth. With a star topology, expanding
a network is easily done by adding another
• Cable type. The most common cable in schools
is unshielded twisted pair, which is most often
used with star topologies.
Two types of transmission technologies are
2. Broadcast Network
Single communication channel is shared by all
the machines in the network.
1. Point to Point Network
Data is routed directly from source machine to
destination machine directly.