1. Data Communication Networks
Lec 2

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

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

4. Effectiveness of DC Delivery Accuracy Timeliness Jitter
Should reach as they produce, without delay, real-time transmission
Jitter
Variation in arrival time, delay will result in poor quality

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

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

7. Data Flow Simplex Half-duplex Full-duplex Keyboard, monitors
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

8. 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

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

10. 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

11. Network Criteria Reliability Security 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.

12. Physical Structure
Point-to-point
Multipoint

13. Categories of Networks
LAN
MAN
WAN

14. 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.

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

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

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

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