Data Communication and Networking Week 2 1Data Com & Networks LLU by Bilal Ahmad.

Data Com & Networks LLU by Bilal Ahmad

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Data Communication and Networking

Week 2


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Introduction Data Communication and Networking are

changing the way we do business. In order to have best productivity

decisions has to be made quickly. Decision makers love to have accurate

information at no time. Why to wait for DHL or TCS or Pakistan

Post when mail can be delivered via Email.

Business today relies on computer networks and internetworks.


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Introduction (Continued) But before we ask how quickly we can have the

accessibility we need to find what are Networks, How they Operate, What type of technologies are available in the market, which design best fills which set of needs.

Similar to the fact that computers has brought a tremendous change for business, data communication and networking is revolutionary.

Just imagine the internet connectivity, it was very slow and expensive. Now we do have broadband with optical cable.

Before a twisted cable was used and optical cable can operate on speed of light.


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Overview This lecture will address two issues and in the

next lecture remaining two issues will be discussed;

1. Data Communication2. Networks3. The Internet4. Protocol and Standards First a broad definition of data communications,

then it will be defined “network as highway where you can travel”. The internet will be discussed as a network of networks, and finally different protocols, standards and their differences will be discussed.


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Data Communication When we communicate, we are sharing

information. The sharing can be local or remote. Between individuals communication occurs

face to face Remote communication takes place over

distance. If you take an example of Telecommunication it

includes Telephony, Telegraphy and Television. That reflects communication at a distance. Tele is a Greek Oriented word means ‘far’.

The word ‘data’ refers to information. Data can be text, voice, multimedia etc.


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Data Communication (Continued) Data communication means exchange of

information in the form of data between two devices via some form of transmission media such as a wired cable or air in case of wireless medium.

For Data Communications to occur, the communicating devices must be a part of a communication system made up of combination of hardware (Physical Equipment ) and Software (Programs).

The effectiveness of Data Communication depends on four fundamental characteristics; delivery, accuracy, timelines and jitter.


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Fundamental Characteristics to determine the effectiveness

1. Delivery: Data must be delivered to the correct

destination. 2. Accuracy: The information should be received

accurately. Data if altered in transmission or left uncorrected are unusable.

3. Timelines: The data must reach on time. Just imagine

not every time you will be sending emails. If you are transmitting a video and the message is not reached on time, it will cause severe problems to your transmission.


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Fundamental Characteristics to determine the effectiveness

4. Jitter: Jitter refers to the variation in the

packet arrival time. It is the uneven delay in the delivery of Audio or video Packets. For example lets assume that you are having a video conference calls or you are talking to someone using Skype. You will observe some jitters on the video if delay has been caused in the transmission. There are so many factors that can cause delays. Slow Network, Poor Cable infrastructure etc can cause delays.


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Components of Data Communication


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Components Explained Message: The message is the information in the form

of data to be communicated. Popular forms are text, numbers, pictures, audio and video.

Sender: The device that sends the data is called a

sender. Example of senders can be computer, mobile phones, video cameras etc.

Receiver: The Devices that receives the data is called a

receiver. Again receiver should be according to the transmitter.


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Components Explained Transmission Medium: The Transmission medium is the physical path by

which a message can be conveyed. Message travels from the sender to receiver. In case of mobile phones the device is considered to be a transmitter and a receiver at the same time. Examples of transmission media are cables, twisted pair cables, network cables, fiber optic cables, radio waves.

Protocol: A set of rules that governs to data

communications. It represents an agreement between the two devices. Without protocol you may be able to connect two devices but there will be no communications.


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Data Representation Information today comes in different forms such

as; Texts Examples are 32 bit/ 64 bit etc. Numbers Example is ASCII Images Composed of Pixels Audio Video Both Audio and Video are different from Text,

Numbers and Images. They are real time analog signals which are converted to discrete values.


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Data Flow


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Networks A Network is a set of devices (often

referred as nodes) connected by communication links. A node can be a computer, a printer, or any other device capable of transmitting and receiving data generated by other nodes.

Distributed Processing: Most Networks use distributed

processing. A task is divided among multiple computers. Example of a server that is used to manage different computers. Remember we do have limited resources and we need to achieve the best results.


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Criteria of a Network A Network must be efficient and effective.

The criteria is;1. Performance2. Reliability3. Security

Here is a group activity for you. Consider four mobile networks Ufone, Warid, Telenor and Mobilink. On the basis of above criteria debate which is the best network? And why it is the best network. Work in groups of 2 or 3.


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Physical Structures Before discussing Networks we need to

define some network attributes. A network is two or more devices

connected through Links. A Link is a communication pathway that

transfers data from one device to another.

For simplicity consider a link as a line drawn between a sender and receiver.

Two types of connection are point to point and point to multipoint.


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Topology Topology term is used for the Physical

Topology it refers to way how two or more devices in a network are connected. The Physical topology is very important. It depends on the available resources. There are total 4 Topologies, they are;


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Mesh Topology If the communication is Duplex than we

need total links; n (n - 1) / 2, How?


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Star Topology In Star topology, each device has a

dedicated link to the central controller.


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Bus Topology The preceding examples were point to

point, the Bus topology is multipoint. One long cable acts as a backbone to other devices in a Network.


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Ring Topology


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Categories of Network Usually we discuss two types, Local Area

Network and Wide Area Network. LAN’s are usually within a building. Most common topologies are bus, star

and ring. Speeds are 100 or 1000 Mbps. For Long distance communication we use

WAN’s. You know the Internet, I am sure. Mobile Telephony and Internet are the

Perfect Examples of WAN.


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Protocols and Standards In Computer Networks, communication occurs

between entities in a different system. An entity is capable of sending and receiving the information. However two entities cannot simply send bit streams to each other and expect to be understood. For communication to occur there must be a set of defined rules known as protocol.

Protocol defines what is communicated, how it is communicated and when it is communicated.

Syntax refers to the structure and format, semantics for the meaning and timing what data should be send and how fast it should be send.


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Network Models A Network is a combination of Hardware

and software that sends Data from one location to another.

In our daily life we do use the concepts of Layers. Just consider an example of two friends who communicate through postal mail.

You have sender, receiver and carrier. Just try to draw a sketch in your mind, how will be the process.


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Layered Tasks


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The OSI Model Established in 1947, The International

Standard Organization is a multinational body dedicated to worldwide agreement on International Standards.

It is an open system interconnectivity. You have been told that why we need to

have an open system standard? OSI Model is a Layered framework for the

design of a Network systems that allows communication between all types of computer systems.


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OSI Layers: 7 Layered Architecture


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Data Communication and Networking Week 2 1Data Com & Networks LLU by Bilal Ahmad.

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Transcript of Data Communication and Networking Week 2 1Data Com & Networks LLU by Bilal Ahmad.