Introduction to Computer Networks

Estudies4you 19:08
Introduction to Data Communication
Over View:
Why are we studying this subject?
  • To develop practical networking knowledge and skills in a professional environment, with emphasis on hands on approach.
  • To learn to design, build and maintain computer networks capable of supporting higher organizations
  • To configure the network routers and switches, so that both LAN and WAN traffic successfully traverses the network
  • To verify the proper configuration of a computer network
  • To troubleshoot  the network problems and successfully implement the appropriate solutions to the problems.
How t is linked with other subjects/branches of engineering, if applicable?
  • One application of a computer network in a field is distributed computing, where a network system will allow the computers to interact with a common goal.
  • Research and various inventions in core areas like electrical and electronics engineering has led to the design of a computing machine and communication network
  • It is used in the field of computational complexity theory, where a computer can networked with other computers in the event that something needs to be fixed in one go, all at once.
Introduction to the Data Communication:
  • At end of this topic, you will be able to:
  • Identify the different types of data we use and the need for its transfer from one place or person to another
  • Understand the need of different components of a data communication system designed to achieve the transfer of data
  • Identify the method for measuring the performance of a communication system
  • Visualize the storage of different types of data
  • Know the different ways of exchanging data or information in a communication system
  • Understand the need for a network of communication systems
  • Know the various issues involved in designing a network
  • Know the internet
By the end of this topic, you will be able to
  • Effectively present ideas in a logical framework in a variety of forms with proper language structure and mechanics
  • Understand the technical aspect of telecommunication system and internet as well as their roles in business environment
  • Identify the different types of network devices and their functions within a network
Data + Communication
Introduction to Data Communication, how computer networks is related to other subjects, what is data communication systems, what is Hardware Component, what is Software Component, Effectiveness of Data Communication System, Data Representation in computer networks,Different forms of Data in computer networks, data flow models in computer networks, half duplex in computer networks, full duplex in computer networks, simplex in computer networks, difference between half duplex and full duplex, what is network, what are the issues in network design, what is physical structure in networks, what is point to point in networks, what is multi point in networks, what is physical topology in networks, types of typologies in computer networks, define Personal Area Network, define Local Area Network, define Metropolitan Area Network, define Wide Area Network, what is Switched WAN, Interconnection of Networks, define internet, history of internet, what is internet service provider,
Communication:
To exchange thoughts, emotions, opinions or ideas by writing, speaking or gesturing (in human interactions), to exchange electrical or electromagnetic waves (in machine interactions)
Data:
Some information that is presented for communication in some format agreed upon by the communicators.

Data Communication Systems:
Introduction to Data Communication, how computer networks is related to other subjects, what is data communication systems, what is Hardware Component, what is Software Component, Effectiveness of Data Communication System, Data Representation in computer networks,Different forms of Data in computer networks, data flow models in computer networks, half duplex in computer networks, full duplex in computer networks, simplex in computer networks, difference between half duplex and full duplex, what is network, what are the issues in network design, what is physical structure in networks, what is point to point in networks, what is multi point in networks, what is physical topology in networks, types of typologies in computer networks, define Personal Area Network, define Local Area Network, define Metropolitan Area Network, define Wide Area Network, what is Switched WAN, Interconnection of Networks, define internet, history of internet, what is internet service provider,
Hardware Component:
1.       Sender : Device that creates and transmits data
2.       Receiver: Device that receives and consumes data
3.       Transmission Medium: Path over which the data travels from sender to receiver
Software Component:
4.       Message: information (data) to be communicated.
5.       Protocol: set of rules that govern data communications.

Effectiveness of Data Communication System
The effectiveness of a data communication system depends four fundamental characteristics
1.       Delivery: the system must be delivered to the correct destination
2.       Accuracy: System must deliver the data accurately
3.       Timeliness: System must deliver data in time
4.       Jitter: The variation in the packet arrival time.

Data Representation
Before we see how to represent data, we must know the different forms or types of data we use in our lives.
Different forms of Data
Form
Example
Binary Form
Size
Text
“ I am half engineer” (Unicode, ASCII)
1001001100000100001110110110000010001110110010100110100000100010111101101101111110100011011
1.43 bytes
Number
23; 321.15; -54.0001; (directly converted to a binary number)
000010111 (23)
1 byte
Image
734 x 349 px
Size too large to fit in here
PNG 18 kb
JPEG 71.6 KB
BMP 304.4 KB
Audio
(MP3, WAV, AIFF)
Size is too large to fit here
MP3 70.8 KB
Video
(DAT, AVI, MPEG-4, SWF)
Size is too large to fit here
SWF 2.3`1 KB

  • A machine like the digital computer system either stores, or processes or sends or receives these kinds of data.
  • This means that they all can be converted into binary form that is in 1’s and 0’s and of course they will have some size.
  • But, out of the five forms the audio and video data differ in their nature from the other three.
  • For example a piece of audio and video data is huge in size as compared to the other three.
  • Another difference is that you ‘play’ a video or audio data which is not the case with the other three.
  • So they differ in the way they work when they are opened or played.
  • Based on this, we have two ways of representing the binary conversion of the different forms – one is BLOCK oriented and the other is STREAM oriented representation of the binary data.
Data Representation:
1.       Stream Oriented – Audio - Video
2.       Block Oriented – Text – Number - Image

Data Flow:
There are three modes of communication
Simplex
Half-Duplex
Full-Duplex

Simplex: Communication is unidirectional. Only one of two devices on a link can transmit; the other can only receive. Entire capacity of the channel is available. E.g. Keyboards and traditional monitors.
Half-Duplex: Each station can both transmit and receive, but no at the same time. When one device is sending the other can only receive, and vice versa. Entire capacity of the channel is available. E.g. Walkie talkies and CB (Citizens Band) radios.

Full-Duplex or Duplex: Both stations can transmit and receive simultaneously. Capacity of the medium, is divided between the two directions e.g., telephone network.

Networks:
A set of devices connected by communication links or transmission media for the purpose of achieving data communication is termed as a network.
Devices can be computer, printer and other devices capable of sending and/or receiving data generated by other devices on the network.
Computer network is an interconnected set of autonomous computers.
Network is for sharing resources, exchanging information and distributed processing within the interconnected devices through long distance.

Network Design
Issues in network design
Network criteria:
                Performance (throughput, delay)
                Reliability
                Security
Physical Structure (Network hardware)
Type of connection
                Point to Point
                Multipoint
Point to Point
A dedicated link between two devices.
The entire capacity of the link is reserved for transmission between those two devices.
Multipoint
More than two specific devices share a single link;
The capacity of the channel is shared, either spatially or temporally.
If several devices can use the link simultaneously, it is a spatially shared connection.
If users must take turns, it is temporarily shared connection.
Physical Topology
Bus: One long cable acts as a backbone to link all the devices in a network
Ring: Each device has a dedicated point to point connection with only the two devices on either side of it.
Star: Each device has a dedicated point to point link only to a central controller, usually called a hub.
Mesh: Every device has a dedicated point to point link to every other device; n(n-1)/2
Hybrid: Network can be hybrid of two or more topologies.
Interprocessor distance
Processors located in same
Example
1 m
Square meter
Personal area network
10 m
Room
Local area network
100 m
Building
1 km
Campus
10 km
City
Metropolitan area network
100 km
Country
Wide area network
1000 km
Continent
10000 km
Planet
The Internet

Personal Area Network (PAN) devices communicate over the range of a person. E.g., a wireless network that connects a computer with its peripherals.
Local Area Network (LAN) privately owned and links the devices in a single office, building or campus
Metropolitan Area Network (MAN) a network with a size between a LAN and WAN.
Wide Area Network (WAN) spans a large geographical area often a country or continent.

Switched WAN:
A WAN can be as complex as the backbones that connect the internet or as simple as a dial-up line that connects a home computer to the internet. We refer to the first as a switched WAN. The switched WAN connects the end systems which usually comprise of a router (internetworking connecting device) that connects to another LAN or WAN.

Interconnection of Networks:
Repeater: It takes bits from one port and forwards it to the other port after amplification and equalization.
Hub: it takes inputs from one port and forwards it to all other ports after amplifying the signal also called multiport repeater.
Switch: it connects different LAN’s together or creates segments of a LAN to improve throughput. By its function it can be called as an intelligent, hub, because it does not forward every incoming frame at a port to all other ports, but it identifies the destination and places it on to the respective port.
Router: it connects two or more networks together.
Gateway: A machine that makes a connection between two or more networks and provides the necessary translation, both in terms of hardware and software.
Modem: A device that connects a computer system to analog lines. It performs modulation and demodulation.

The Internet
  • The internet is a structured, organized communication system that brings together a huge amount of information in an organized manner to out fingertips, so that we can use it.
  • The internet consists of a collaboration of more than thousands of interconnected networks
  • In 1967, at an Association for Computing Machinery (MCM) meeting, ARPA presented its ideas for ARPANET.
  • By 1969, ARPANET was set and working.
  • In 1972, Vincent Cerf and Bob Kahn, both of whom were part of the core ARPANET group, collaborated on what they called the internetting project.
  • Cerf and Kahn’s landmark 1973 paper outlined the protocols to achieve end-to-end delivery of packets. This paper on transmission control protocol (TCP) included concepts such as encapsulation, the datagram, and the functions of a gateway.
The Internet Today
It is made up of many wide-area and local area networks joined by connecting devices and switching stations
New networks are added to the existing networks.
Existing networks add addresses of new networks
Internet Service Provider (ISP) are the internet connection service providers
International ISP
National ISP
Regional ISP
Local ISP

To provide connectivity between the end users, these backbone networks are connected by complex switching stations (normally run by a third party) called network access points (NAP’s).
As the top of the hierarchy are the international service providers that connect nations together.
Regional internet service providers or regional ISP’s are smaller ISP’s that are connected to one or more national ISP’s
They are at the third level of the hierarchy with a smaller data rate.
Local internet service providers provide direct service to the end users. The local ISP’s can be connected to regional ISP’s or directly to national ISP’s.
Most end users are connected to the local ISP’s


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