Data Communication Networks Lec 2 Data Communication Communications

Data Communication Networks Lec 2

Data Communication • Communications is sharing information. • Local, remote. • “Telecommunication” means communications at a distance. • Data is the form of information presented.

Data Communication • Defined as the exchange of data between two devices via some form of transmission medium. • Software and hardware is the part.

Effectiveness of DC • Delivery • Accuracy • Timeliness – Should reach as they produce, without delay, realtime transmission • Jitter – Variation in arrival time, delay will result in poor quality

Components • Message – Text , numbers, pictures , video • Sender – Computer , workstation, telephone set etc • Receiver – Computer , workstation, telephone set etc • Transmission media – Cables, radio waves • Protocol – Set of rules

Data Representation • Text – Sequence of bits • Numbers – Bit patterns , numbers is converted to binary number • Images – Pixels • Audio – Continuous , not discrete • Video – Can be continuous entity or combination of images.

Data Flow • Simplex – Keyboard, monitors • Half-duplex – Each can transmit or receive but not at same time – Walkie-talkie • Full-duplex – Both stations can transmit and receive at the same time. – Telephone

Networks • A network is set of devices connected by communication links. • Devices can be computer, printer, or any other device capable of sending and/or receiving data

Distributed Processing • Task is divided among multiple computers. • Each handle a subset.

Network Criteria • Performance – Transit and response time – Transit amount of time required for a message to travel from one device to another. – Response time is the elapsed time between inquiry and a response. – Number of users, type of transmission medium, connected hardware – Efficiency of hardware. – Throughput(average rate of successful message delivery ) and delay

Network Criteria • Reliability – Frequency of the failure – Time it takes to recover from a failure. • Security – Protection from unauthorized access, – Protecting data from damage – Implementing policies for recovery from breaches and data loss.

Physical Structure • Point-to-point • Multipoint

Categories of Networks • LAN • MAN • WAN

Local Area Network(LAN) • Privately owned and link the devices in a single office, building or campus. • Designed to allow resources to shared personal computers e. g. hardware, printer data etc.

Metropolitan Area Network(MAN) • Lies between size of LAN and Wan. • Covers the area inside city or a town.

Wide area Network(WAN) • Provides long distance transmission of data. • Large geographical area that comprise of country or even whole world.

Internetwork • LAN , WAN and MAN are not seen in isolation. • Mostly are interconnected, form an internetwork or a internet.

Physical Topology • Refer to way in which network is laid out physically. – Mesh – Star – Bus – Ring