Data Communication
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Transcript of Data Communication
DATA COMMUNICATIO
NWaqas Ali Sahito
LecturerDepartment of Computer Science
DATA COMMUNICATION “Data Communication is the exchange of
Information from one entity to the other using a Transmission Medium”.
As you can clearly notice, the definition of Data Communication although Simple leaves many questions unanswered:
¾ Exchange?????? ¾ Information????? ¾ Entities??????? ¾ Transmission???? ¾ Medium????
CONT… Or we Can Say When we communicate, we are sharing
information, this sharing can be local or remote, between individuals, local
communication normally occurs face to face, while remote communication takes place over distance , the work “tele-communication ” is best example of communication over distance
CONT… Data Communication are the exchange
of data between two devices via some form of transmission medium, such as wireless or cable, for data communication to occur, communication devices must be part of communication system made up of combination of hardware and software,
CHARACTERISTICS OF DATA COMMUNICATION The effectiveness of Data
Communication depends on these fundamental characteristics.
Delivery Accuracy Timeliness Jitter
CHARACTERISTICS OF DATA COMMUNICATION Delivery: The system must deliver the
data to correct destination, data must be received by intended device or the user and only by that device or user.
Accuracy: The System must deliver the data accurately, Data altered in transmission and left uncorrected are unusable
CHARACTERISTICS OF DATA COMMUNICATION Timeliness: The system must deliver
data in timely manner, data delivered late are useless. Incase of video and audio timely delivery means data must be delivered as it is produced, in the same order they are produced and without significant delay. This type of delivery is called “Real Time Transmission”.
CHARACTERISTICS OF DATA COMMUNICATION Jitter: It refers to the variation in the
packet arrival time, It is the uneven delay in the video or audio packets,
For example: Video packets are sent every 30 ms, if some packets arrive at 30 ms delay and some packets arrive at 40 ms delay than uneven quality in the video will be the result.
FEW KEY WORDS Packet: A technology for breaking
digital data up into small units (packets) for data transmission.
Transmission: Sending and receiving the data is called transmission.
Data: Information presented in whatever form is agreed upon by the both parties ( sender and receiver) is called data.
COMPONENTS OF DATA COMMUNICATION Data Communication has Five
components.
COMPONENTS OF DATA COMMUNICATION Message Sender Receiver Transmission medium Protocol
COMPONENTS OF DATA COMMUNICATION Message: Information or Data to be
communicated, It can be text, numbers, video or any combination of these. In short anything that can be represented using binary bits
COMPONENTS OF DATA COMMUNICATION Data Communication Messages
Files (meaningful collections of records) Data/information requests (database queries,
Web page requests, etc.) Responses to requests and commands or error
messages Status messages (about the network’s
functional status) Control messages transmitted between
network devices to control network traffic Correspondence among network users
COMPONENTS OF DATA COMMUNICATION SENDER: Device that sends the data message,
Can be a Computer , Workstation, Video camera etc, As already discussed, the data from the sender might not be in the appropriate format for the transmission medium and will need to be processed
COMPONENTS OF DATA COMMUNICATION RECEIVER
Device that receives the message, Can be a computer, workstation, Television etc At times, the data received from the transmission medium may not be in a proper form to be supplied to the receiver and it must be processed
COMPONENTS OF DATA COMMUNICATION Transmission medium Physical path that a message uses to travel
from the Sender to the receiver , Can be a Copper Cable (Telephone), Coaxial Cable (Cable TV), Fiber Optic Cable, LASERS or Radio Waves (Wireless Medium).We will see that Data needs to be transferred in the form of ELECTROMAGNETIC signals and The Transmission Medium should be capable of carrying these EM Signals
Transmission Media
COMPONENTS OF DATA COMMUNICATION PROTOCOL
Set of Rules Governing Communication Represents an Agreement between communication devices. Without Protocol, two devices may be connected but they will not be able to communicate
For-example: Consider the communication between two individuals. They can only communicate provided they both speak the same language.
Data Flow
SIMPLEX In simplex mode the communication is
uni-directional as one way road, only one of the two devices on the link can transmit, keyboards and traditional monitors are the examples of simplex devices, the keyboard can only introduce input while the monitor can only accept output, It can take entire capacity to send the data in one direction
Simplex
HALF DUPLEX In half duplex each station can send and
receive the data but one at a time, when one device is sending the other device can only receive, the half duplex transmission takes full capacity of the line for whichever device is sending the data, “ Walkie Talkie is the best example of half duplex.
Half-Duplex
DUPLEX / FULL DUPLEX In full duplex mode ( also called duplex)
both the devices can send and receive the data at the same time, In full duplex the signal going in the one direction share the capacity of the line with signals going in the other direction.
The sharing may occur in two ways, Either the link may contain two separate
physical transmission paths, one for sending and one for receiving.
CONT.. Or the capacity of the line is divided into
the signals travelling in both directions. One common example of the full duplex
communication is “ Tele-phone “
Full-Duplex
NETWORK A network is set of devices ( often
referred as nodes) connected by a communication link. A node can be a computer, printer or any other device that can be capable of sending and receiving data generated by other node on the network.
DISTRIBUTED PROCESSING Most of networks use distributed
processing, in which a task is divided into multiple computers, Instead of one single large machine being responsible for all aspects of the process, separate computers ( usually PCs or workstations) handle a subset.
NET WORK CRITERIA A network must meet certain number of
criteria, The most important are,
Performance Reliability Security
NETWORK CRITERIA Performance Performance can be measured in many
ways, including transit time and response time, where transit time is amount of time required for a message to travel from one device to an other, and response time is the elapsed time between an inquiry and response.
CONT… The performance of the network
depends on number of factors, including the number of users, the type of transmission medium, the capability of connected hardware and efficiency of the software, Performance is often measured in two metrics: Throughput and Delay.
CONT… We often need more throughput and
less delay, however these two metrics are contradictory, If we try to send more data on the network, we may increase the throughput but we increase the delay as well because of congestion in the network
CONT.. Reliability In addition to the accuracy the network
reliability is measured by the frequency of failure, the time it takes to the link to recover from the failure, and the network’s robustness in a catastrophe.
CONT.. Security Network security issue includes
protecting data from un authorized access, protecting data from damage and development, and implementing policies and procedures from breaches and data losses.
Thank You
Figure 2-15
WCB/McGraw-Hill The McGraw-Hill Companies, Inc., 1998
Figure 2-16
WCB/McGraw-Hill The McGraw-Hill Companies, Inc., 1998
Local Area Network
Figure 2-16-continued
WCB/McGraw-Hill The McGraw-Hill Companies, Inc., 1998
Local Area Network
Figure 2-17
WCB/McGraw-Hill The McGraw-Hill Companies, Inc., 1998
Metropolitan Area Network
Figure 2-18
WCB/McGraw-Hill The McGraw-Hill Companies, Inc., 1998
Wide Area Network
Figure 2-19
WCB/McGraw-Hill The McGraw-Hill Companies, Inc., 1998
Internetwork (Internet)