This document discusses data communication and computer networks. It defines data communication as the electronic transmission of textual, numeric, audio or video data over long distances. Computer networks allow data communication between computers. Different types of networks include local area networks (LANs) connecting computers in close proximity, wide area networks (WANs) connecting multiple LANs over large geographical areas, and metropolitan area networks (MANs) connecting LANs within cities. The largest computer network is the Internet, which connects networks worldwide through gateways. Networks can be organized in different topologies like star, ring or hybrid configurations. Network protocols like TCP/IP establish rules for communication between connected computers. Common network applications involve bulletin boards, information services,

1. DATA COMMUNICATION
AND NETWORKS
• Computers can be used in two modes:
stand-alone mode and communication mode
• Communication of messages
electronically over a long distance is
known as telecommunication

2. DATA COMMUNICATION
AND NETWORKS contd..
• When a computer is used to transmit
electronically textual, numeric, audio or
video data, to a distant location, the
process is called data communication
• The technology that combines
computer technology and
telecommunication technology has
come to be known as information
technology

3. DATA COMMUNICATION
USING MODEMS
• Computer to computer
communication can be made using
modems and using networks
• The devices that perform these
special tasks of encoding and
decoding data are known as
modems, a term derived from the
words modulation and demodulation

4. COMPUTER NETWORKS
• Based on geographical area
• Local area networks (LANS)
• Wide area networks (WANS)
• Metropolitan area networks (MANS)
• International network (Internet)
• Intranet

5. COMPUTERNETWORKS
contd..
• Based on how computer nodes are
used
• Client-server networks (CSNS)
• Peer-to-peer networks (PPNS)
• Value-added networks (VANS)

6. Local Area Networks
• A network of computers and other devices
located relatively close to each other in an
office (or in a building) and connected by
a wire (or a wireless link) is called a local
area network (LAN)
• A storage device that is shared by all the
computers is called the file server
• A computer (or any other device)
connected to the networking cable is
called a node

7. Wide Area Networks
• A network that connects two or more
LANs spread across a large
geographical area is called a wide area
network (WAN)

8. Metropolitan Area Networks
• Metropolitan area networks (MANs) are the
networks that are in between LANs and
WANS. These networks are created to
provide city-wide services in large cities
and thus the name metropolitan. MANs
fill the need of extending LAN capabilities
to larger geographic areas. They are used
to connect LANs across different offices
in a city or to link LANs to WANS

9. Internet
• This requires connecting together
different types of networks all over
the world by using systems known
as gateways. The gateway
computers make connections and
provide necessary interface. A
collection of networks connected to
each other (network of networks) is
called the Internet

10. Intranet
• It refers to a network that belongs to
a particular organization or company.
It uses the same tools and protocols
that are used in internet and
therefore it can be used like the
internet

11. Client-Server Networks
• Another way of organising networks is to
make one node (computer) to serve the
storage needs of all other nodes
(computers) in the network. This kind of
arrangement is called a client-Server
network (CSN). The computer that stores
data and programmes is called the server
and the computer that uses the data and
software of the server is called the client

12. Peer-to-Peer Networks
• In this arrangement each node has
access to the resources of other
nodes. That is users can have
access to the hard disks and printers
attached to other computers

13. Value-Added Networks
• These services may include access
to different types of databases, e-
mail, games, etc. WANs that add
such services to the existing
capabilities are known as value-
added networks (VANs)

14. NETWORK TOPOLOGIES
• An arrangement of connections that link
computers and other devices in a network
is known as network topology
• Hierarchical (or tree) topology
• Linear bus (or horizontal) topology
• Star topology
• Ring (or hub) topology
• Hybrid (or mesh) topology

15. Hierarchical Topology
• microcomputers are connected to
minicomputers which intrun are
connected to a large mainframe
computer

16. Linear Bus topology
• connects several nodes (computers
and other devices) with a single
network cable. All data travel along a
single communication cable to which
the nodes are connected

17. Star Topology
• Uses a central controlling computer that
controls and routes all communication
requests. Each node is directly linked
to the central computer known as the
hub. The arrangement is similar to the
hierarchical one, except that the star
topology uses only a single level of
hierarchy

18. Ring Topology
• All computers and devices are
connected in a circular form. Each
node is connected to the next one.
In most cases, data flows in one
direction only

19. Hybrid Topology
• Two or more of the above topologies
may be combined to form the hybrid
topology. Due to the multiplicity of
paths available, data can be routed
around failed links or busy nodes.

20. NETWORK PROTOCOLS
AND SOFTWARE
• When computers use a common
channel for data communication,
they follow some rules and
procedures to prevent any data
collisions. These procedures (a set
of standards for communication) are
called the network protocols

21. NETWORK PROTOCOLS AND
SOFTWARE
• A protocol is simply an agreement
between the communicating parties
on how communication is to
proceed. Violating the protocol will
make the communication more
difficult, if not impossible

22. NETWORK PROTOCOLS AND
SOFTWARE
• The Internet uses a protocol known
as transmission control protocol /
internet protocol (TCP/IP) for routing
information over the network.
Internet protocol incorporates basic
rules such as the composition of
internet address, the size of the data
to be delivered, and so forth

23. NETWORK APPLICATIONS
• Bulletin board service (BBS)
• Information services
• Telecomputing
• Teleconferencing
• Workgroup computing
• Electronic funds transfer (EFT)
• Electronic data interchange (EDI)
• Electronic commerce