This document provides an overview of computer networks and data communication concepts. It defines key terms like bandwidth, attenuation, data rate, and channel capacity. It describes the basic components of a data communication system including the message, sender, receiver, transmission medium, and protocols. It also discusses standard making organizations like IEEE, ANSI, and ITU and their roles in developing networking standards. Finally, it outlines characteristics of data communication systems like delivery, accuracy, timeliness, and jitter.

1. UNIT-I
Introduction to Networks

2. CO1:Interpret the concepts, components, standards and
topologies. Explain layered architecture of OSI and
TCP/IP model.- K2 LEVEL
Contents:
Data Communication: Components - Protocols and Standards -
Standard making organizations - data rate and Channel capacity,
Line configuration, Topology of networks, Transmission modes,
Digital Data Transmission, Categories of Networks, Inter-Networks,
OSI model, TCP/IP Model, Networking and internetworking devices,
Switching: Circuit switching - Packet switching - Message switching.
UNIT-I
INTRODUCTION TO NETWORKS

3. Components of a data communication system
The word data refers to information presented in whatever form
is agreed upon by the parties creating and using the data.
Data communications are the exchange of data between
two devices via some form of transmission medium such as a
wire cable.

4. 1. Message. The message is the information (data) to becommunicated.
---Popular forms of information include text, numbers,
pictures, audio, and video.
2. Sender. The sender is the device that sends the data message.
--- It can be a computer, telephone handset, video camera,
and so on.
3. Receiver. The receiver is the device that receives the message.
---It can be a computer, telephone handset, television, and
so on.
4.Transmission medium. The transmission medium is the physical path
by which a message travels from sender to receiver.
---Some examples of transmission media include twisted-
pair wire, coaxial cable, fiber-optic cable, and radio waves
5.Protocol. A protocol is a set of rules that govern data communications. It
represents an agreement between the communicating devices. Without a
protocol, two devices may be connected but not communicating.
---just as a person speaking French cannot be understood
by a person who speaks only Japanese.

5. Basic Definitions
Bandwidth
Amount of data that can be transferred from one point to another in
a certain time period
Attenuation
Loss of power in a signal as it travels from the sending device to
the receiving device
Channel Capacity:
The tight upper bound on the rate at which information can be
reliably transmitted over a communication channel.
Data Rate:
the transmission speed, or the number of bits per second
transferred.

6. COMPUTER NETWORKS
Computer network consists of two or more computers
that are linked in order to share resources, exchange data files or to
allow electronic communication. The computers on a network may
be linked through cables, telephone lines, radio waves, satellites or
infrared light beams.
There are two aspects of computer networks – hardware
and software.
Hardware includes physical connection between
two machines by using adaptors, cables, routers, bridges etc.
software includes a set of protocols. Protocols
define a formal language among various components. It makes
hardware usable by applications.

7. CHARACTERISTICS OF DATA COMMUNICATION
SYSTEM
Delivery-
The system must deliver to the correct destination
Accuracy-
The system must deliver the data accurately.
Timeliness-
The system must deliver data in a timely manner.
Jitter-
uneven delay-variation in arrival time.

8. PROTOCOLS
 A protocol is a set of rules that govern data
communications. It determines what is communicated,
how it is communicated and when it is communicated.
 The key elements of a protocol are
1. Syntax
2.Semantics
3.Timing

9. 1.Syntax:
 The term syntax refers to the structure or format of the data,
meaning the order in which they are presented.
 For example, a simple protocol might expect the first 8 bits of
data to be the address of the sender, the second 8 bits to be the
address of the receiver, and the rest of the stream to be the
message itself.

10. 2.Semantics:
 The word semantics refers to the meaning of each section of bits.
How is a particular pattern to be interpreted, and what action is to
be taken based on that interpretation?
 For example, does an address identify the route to be taken or the
final destination of the message?
3.Timing:
The term timing refers to two characteristics: when data should be
sent and how fast they can be sent.
For example, if a sender produces data at 100 Mbps but the receiver
can process data at only 1 Mbps, the transmission will overload the
receiver and some data will be lost.

11. Standards
 Common set of rules followed

12. Standards
 Standards are essential in creating and maintaining an open and
competitive market for equipment manufacturers and in
guaranteeing national and international interoperability of data
and telecommunications technology and processes.
 Standards provide guidelines to manufacturers, vendors,
government agencies, and other service providers to ensure the
kind of interconnectivity necessary in today's marketplace and in
international communications.
 Data communication standards fall into two categories: de facto
(meaning "by fact" or "by convention") and de jure (meaning "by
law" or "by regulation").

13. a. De facto:
 Standards that have not been approved by an organized body but
have been adopted as standards through widespread use are de
facto standards.
 De facto standards are often established originally by
manufacturers who seek to define the functionality of a new
product or technology.
b. De jure:
 Those standards that have been legislated by an officially
recognized body are de jure standards.

14. Standard Making Organizations
(Standards creation Communities)
1. IEEE (Institute of Electrical and Electronics Engineers)
2. ANSI (American National Standards Institute)
3. ITU (International Telecommunications Union - formerly
CCITT)
4. ISO (International Organization for Standards)
5. EIA (Electronic Industries Association)
6. ETSI (European Telecommunications Standards Institute)
7. W3C - World Wide Web Consortium

15. 1. IEEE (Institute of Electrical and Electronics
Engineers)
 The purposes of the organization as "scientific and educational,
directed toward the advancement of the theory and practice of
Electrical, Electronics, Communications and Computer
Engineering, as well as Computer Science, the allied branches of
engineering and the related arts and sciences.
 “ The IEEE is incorporated under the Not-for-Profit Corporation
Law of the state of New York”, United States.
 It was formed in 1963 by the merger of the Institute of Radio
Engineers (IRE, founded 1912) and the American Institute of
Electrical Engineers (AIEE, founded 1884). It has more than
400,000 members in more than 160 countries, 45% outside the
United States.

16.  In pursuing these goals, the IEEE serves as a major publisher of
scientific journals and a conference organizer. It is also a leading
developer of industrial standards (having developed over 900
active industry standards) in a broad range of disciplines,
including electric power and energy, biomedical technology and
health care, information technology, information assurance,
telecommunications, consumer electronics, transportation,
aerospace, and nanotechnology.
 IEEE develops and participates in educational activities such as
accreditation of electrical engineering programs in institutes of
higher learning.
 IEEE is one of the leading standards-making organizations in the
world.
 IEEE performs its standards making and maintaining functions
through the IEEE Standards Association (IEEE-SA).

17.  IEEE standards affect a wide range of industries including: power
and energy, biomedical and health care, Information Technology
(IT), telecommunications, transportation, nanotechnology,
information assurance, and many more.
 In 2005, IEEE had close to 900 active standards, with 500
standards under development. One of the more notable IEEE
standards is the IEEE 802 LAN/MAN group of standards which
includes the IEEE 802.3 Ethernet standard and the IEEE 802.11
Wireless Networking standard.

18. 2. ANSI (American National Standards Institute)
 Though ANSI itself does not develop standards, the Institute
oversees the development and use of standards by accrediting the
procedures of standards developing organizations.
 ANSI accreditation signifies that the procedures used by standards
developing organizations meet the Institute's requirements for
openness, balance, consensus, and due process.

ANSI was originally formed in 1918, when five engineering
societies and three government agencies founded the American
Engineering Standards Committee (AESC). In 1928, the AESC
became the American Standards Association (ASA).
 In 1966, the ASA was reorganized and became the United States
of America Standards Institute (USASI). The present name was
adopted in 1969.

19. Prior to 1918, these five engineering societies:
American Institute of Electrical Engineers (AIEE, now IEEE)
American Society of Mechanical Engineers (ASME)
American Society of Civil Engineers (ASCE)
American Institute of Mining Engineers (AIME, now American
Institute of Mining, Metallurgical, and Petroleum Engineers)
American Society for Testing and Materials (now ASTM
International)

20. The American National Standards process involves:
 consensus by a group that is open to representatives from all
interested parties
 broad-based public review and comment on draft standards
 consideration of and response to comments
 incorporation of submitted changes that meet the same consensus
requirements into a draft standard
 availability of an appeal by any participant alleging that these
principles were not respected during the standards-development
process.

21. 3. ITU (International Telecommunications Union -
formerly CCITT)
The specialized agency of the United Nations which is responsible
for information and communication technologies. ITU coordinates
the shared global use of the radio spectrum, promotes international
cooperation in assigning satellite orbits, works to improve
telecommunication infrastructure in the developing world and
establishes worldwide standards.
ITU coordinates the shared global use of the radio spectrum,
promotes international cooperation in assigning satellite orbits,
works to improve telecommunication infrastructure in the developing
world and establishes worldwide standards.

22. ITU also organizes worldwide and regional exhibitions and forums,
such as ITU TELECOM WORLD, bringing together representatives
of government and the telecommunications and ICT industry to
exchange ideas, knowledge and technology.
The ITU is active in areas including broadband Internet, latest-
generation wireless technologies, aeronautical and maritime
navigation, radio astronomy, satellite-based meteorology,
convergence in fixed-mobile phone, Internet access, data, voice, TV
broadcasting, and next-generation networks.

23. 4. ISO (International Organization for Standards)
widely known as ISO, is an international standard-setting body
composed of representatives from various national standards
organizations.
Founded on February 23, 1947, the organization promulgates
worldwide proprietary industrial and commercial standards. It has its
headquarters in Geneva, Switzerland. While ISO defines itself as a
non-governmental organization, its ability to set standards that often
become law, either through treaties or national standards, makes it
more powerful than most non-governmental organizations.

24. In practice, ISO acts as a consortium with strong links to
governments
ISO, is an international standard-setting body composed of
representatives from various national standards organizations the
organization promulgates worldwide proprietary industrial and
commercial standards.
ISO's main products are the International Standards. ISO also
publishes Technical Reports, Technical Specifications, Publicly
Available Specifications, Technical Corrigenda, and Guides .

25. 5. EIA (Electronic Industries Association)
EIA, until 1997 Electronic Industries Association) was a standards
and trade organization composed as an alliance of trade associations
for electronics manufacturers in the United States.
They developed standards to ensure the equipment of different
manufacturers was compatible and interchangable.In 1924
the Associated Radio Manufacturers alliance was formed, which was
renamed to Radio Manufacturers Association (RMA) the same year.
Upcoming new electronic technologies brought new members and
further name changes: Radio Television

26. Manufacturers Association (RTMA) (1950), Radio Electronics
Television Manufacturers (RETMA) (1953) and Electronics
Industries Association (EIA) (1957). The last renaming took place in
1997, when EIA became Electronics Industries Alliance (EIA),
reflecting the change away from a pure manufacturers associationA
standard defining serial communication between computers and
modems e. g. was originally drafted by the radio sector as RS-232.
Later it was taken over by the EIA as EIA-232. Later this standard
was managed by the TIA and the name was changed to the
current TIA-232. Because the EIA was accredited by ANSI to help
develop standards in its areas, the standards are often described as
e. g. ANSI TIA-232 (or formerly as ANSI EIA/TIA-232').

27. 6. ETSI (European Telecommunications Standards
Institute)
an independent, non-profit, standardization organization in the
telecommunications industry (equipment makers and network
operators) in Europe, with worldwide projection. ETSI has been
successful in standardizing the Low Power Radio, Short Range
Device, GSM cell phone system and the TETRA professional mobile
radio system.
Significant ETSI standardisation bodies include TISPAN (for fixed
networks and Internetmachine-to-machine communications). ETSI
inspired the creation of, and is a partner in 3GPP.
ETSI was created by CEPT in 1988 and is officially recognized by
the European Commission and the EFTA secretariat. Based in
Sophia Antipolis (France), ETSI is officially responsible for
standardization of Information and Communication Technologies

28. These technologies include telecommunications, broadcasting and
related areas such as intelligent transportation and medical
electronics.
ETSI has 740 members from 62 countries/provinces inside and
outside Europe, including manufacturers, network operators,
administrations, service providers, research bodies and users — in
fact, all the key players in the ICT arena. convergence) and M2M
(for ETSI has been successful in standardizing the Low Power
Radio, Short Range Device, GSMTETRA professional mobile radio
system.
ETSI was created by CEPT in 1988 and is officially recognized by
the European Commission and the EFTASophia Antipolis (France),
ETSI is officially responsible for standardization of Information and
Communication Technologies (ICT) within Europe.
These technologies include telecommunications, broadcasting and
related areas such as intelligent transportation and medical
electronics.

29. 7. W3C - World Wide Web Consortium
The main international standards organizationWorld Wide Web
(abbreviated WWW or W3).
Founded and headed by Tim Berners-Lee,the consortium is made up
of member organizations which maintain full-time staff for the
purpose of working together in the development of standards for the
World Wide Web. As of 18 February 2011, the World Wide Web
Consortium (W3C) has 322 members.
W3C also engages in education and outreach, develops software and
serves as an open forum for discussion about the Web.

30. W3C also engages in education and outreach, develops software and
serves as an open forum for discussion about the Web.
W3C was created to ensure compatibility and agreement among
industry members in the adoption of new standards.
Prior to its creation, incompatible versions of HTML were offered by
different vendors, increasing the potential for inconsistency between
web pages.
The consortium was created to get all those vendors to agree on a set
of core principles and components which would be supported by
everyone.

31. Line Configurations
 Line configuration refers to the way two or more communication
devices attached to a link.
 Line configuration is also referred to as connection.
 A Link is the physical communication pathway that transfers data
from one device to another.
 For communication to occur, two devices must be connected in
same way to the same link at the same time.
There are two possible line configurations.
1. Point-to-Point.
2. Multipoint.

32. Point to Point Line Configuration
 A Point to Point Line Configuration Provide dedicated link
between two devices use actual length of wire or cable to connect
the two end including microwave & satellite link. Infrared remote
control & tvs remote control.
 The entire capacity of the channel is reserved for
transmission between those two devices. Most point-to-point line
configurations use an actual length of wire or cable to connect the
two ends, but other options, such as microwave or satellite links,
are also possible.

33. Point to point network topology is considered to be one of the
easiest and most conventional network topologies. It is also the
simplest to establish and understand. To visualize, one can consider
point to point network topology as two phones connected end to end
for a two way communication

34. Multipoint Line Configuration
Multipoint Configuration also known as Multi drop line
configuration one or more than two specific devices share a
single link capacity of the channel is shared.
More than two devices share the Link that is the capacity of the
channel is shared now. With shared capacity, there can be two
possibilities in a Multipoint Line Configuration:
•Spatial Sharing: If several devices can share the link
simultaneously, its called Spatially shared line configuration
•Temporal (Time) Sharing: If users must take turns using the
link , then its called Temporally shared or Time Shared Line
Configuration

36. Transmission Modes
 A given transmission on a communications channel between two
machines can occur in several different ways.
 The transmission is characterized by:
 The direction of the exchanges
 The transmission mode: the number of bits sent simultaneously
 Synchronization between the transmitter and receiver
 Types of Transmission mode
 Simplex
 Half Duplex
 Full Duplex

37. Data flow (simplex, half-duplex, and full-duplex)

38. Simplex:
In simplex mode, the communication is unidirectional, as on a one-
way street. Only one of the two devices on a link can transmit; the
other can only receive.
Examples:- Keyboards and traditional monitors are
examples of simplex devices. The keyboard can only introduce
input; the monitor can only accept output. The simplex mode can
use the entire capacity of the channel to send data in one direction.

39. Half-Duplex:
In half-duplex mode, each station can both transmit and receive,
but not at the same time. When one device is sending, the other
can only receive, and vice versa.
Examples:-When cars are traveling in one direction, cars
going the other way must wait. In a half-duplex transmission, the
entire capacity of a channel is taken over by whichever of the two
devices is transmitting at the time. Walkie-talkies is half-duplex
systems.

40. Full-Duplex:
In full-duplex both stations can transmit and receive simultaneously.
The full-duplex mode is like a two-way street with traffic flowing in
both directions at the same time. In full-duplex mode, signals going
in one direction share the capacity of the link: with signals going in
the other direction.
Example:- full-duplex communication is the telephone
network. When two people are communicating by a telephone line,
both can talk and listen at the same time. The full-duplex mode is
used when communication in both directions is required all the
time. The capacity of the channel, however, must be divided
between the two directions.

41. Categories of topology
The term physical topology refers to the way in which a network is laid
out physically. One or more devices connect to a link; two or more links
form a topology.
The topology of a network is the geometric representation of the
relationship of all the links and linking devices (usually called nodes) to
one another.
There are four basic topologies possible: mesh, star, bus, and ring.

42. A fully connected mesh topology (fivedevices)
•In mesh topology every device has a dedicated point-to-point link to
every other device.
•The link carries traffic only between the two devices it connects.
•Duplex-mode
•Advantages:
guaranteed dedicated links
eliminates traffic problems
privacy and security
this makes fault identification easy
•Disadvantages:
cabling and number of IO ports required
wiring is greater than available space
hardware is required for each link – expensive

43. A star topology connecting four stations
•In star topology, each device has a dedicated point-to-point link only to acentral
controller called hub.
•The controller acts as an exchange: if one device wants to send data to another ,it
sends the data to controller, which then relays the data to the another connected
device.
•Advantages:
less expensive
robustness – if one link fails, only that link is affected, other linksremain
active.
•Disadvantages:
dependency of the whole topology on one singlepoint.
star requires less than mesh, each node is linked to the hub. So more
cabling is required .

44. A bus topology connecting threestations
•A bus topology is a multipoint .
•One long cable acts as a backbone to link all the devices in the
network.
•Nodes are connected by bus cable by drop line and taps.
a drop line is a connection running between the deviceand
the main cable
a tap is a connector that either splices or punctures.
•Advantages:
easy of installation
•Disadvantages:
difficult reconnection
addition of new devices require modification or replacement
of the backbone.

45. A ring topology connecting sixstations
•In ring topology each device has a point-to-point connection with only the twodevices
on either side of it.
•Asignal is passed along a ring in one direction, from device to device until it reaches
its destination.
•Advantages:
easy to install and reconfigure
to add or delete a device requires changing only two connections. Theonly
constraints are media and traffic.
•Disadvantages;
unidirectional
a break in a ring can disable the entire network

46. A hybrid topology: a star backbone with three bus networks

47. Categories of Networks
•One way to categorize the different types of computer network
designs is by their scope or scale.
•For historical reasons, the networking industry refers to nearly every
type of design as some kind of area network.
•Common examples of area network types are:
•LAN - Local Area Network
•WLAN - Wireless Local Area Network
•WAN - Wide Area Network
•MAN - Metropolitan Area Network

48. Local Area Network
A LAN connects network devices over a relatively short distance. A
networked office building, school, or home usually contains a single
LAN, though sometimes one building will contain a few small LANs
(perhaps one per room), and occasionally a LAN will span a group of
nearby buildings. In TCP/IP networking, a LAN is often but not always
implemented as a single IP subnet. In addition to operating in a limited
space, LANs are also typically owned, controlled, and managed by a
single person or organization. They also tend to use certain connectivity
technologies, primarily Ethernet and Token Ring.

50. Wireless Local Area Network

51. As the term implies, a WAN spans a large physical distance. The
Internet is the largest WAN, spanning the Earth. A WAN is a
geographically-dispersed collection of LANs. A network device called a
router connects LANs to a WAN. In IP networking, the router maintains
both a LAN address and a WAN address.
A WAN differs from a LAN in several important ways. Most WANs (like
the Internet) are not owned by any one organization but rather exist
under collective or distributed ownership and management. WANs tend
to use technology like ATM, Frame Relay and X.25 for connectivity over
the longer distances.

52. Wide Area Network
A WAN is a network that spans more than one geographical location
often connecting separated LANs. WANs are slower than LANs and
often require additional and costly hardware such as routers,
dedicated leased lines, and complicated implementation procedures.

53. Metropolitan Area Network
A network spanning a physical area larger than a LAN but smaller than
a WAN, such as a city. A MAN is typically owned an operated by a
single entity such as a government body or large corporation.

54. Internetworks
Internetworking is the practice of connecting a computer network
with other networks through the use of gateways that provide a
common method of routing information packets between the
networks. The resulting system of interconnected networks is called
an internetwork, or simply an internet.
The most notable example of internetworking is the Internet, a
network of networks based on many underlying hardware
technologies, but unified by an internetworking protocol standard,
the Internet Protocol Suite, often also referred to as TCP/IP.

55. Networking Model
Two architectural models are commonly used to describe the protocols
and methods used in internetworking.
The Open System Interconnection (OSI) reference model was developed
under the auspices of the International Organization for Standardization
(ISO) and provides a rigorous description for layering protocol functions
from the underlying hardware to the software interface concepts in user
applications. Internetworking is implemented in the Network Layer
(Layer 3) of the model.

56. The Internet Protocol Suite, also called the TCP/IP model of the Internet was not
designed to conform to the OSI model and does not refer to it in any of the
normative specifications in Requests for Comment and Internet standards. Despite
similar appearance as a layered model, it uses a much less rigorous, loosely defined
architecture that concerns itself only with the aspects of logical networking. It does
not discuss hardware-specific low-level interfaces, and assumes availability of a Link
Layer interface to the local network link to which the host is connected.
Internetworking is facilitated by the protocols of its Internet Layer.