Networks & Communications. Comp 277

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1 Networks & Communications Comp 277

2 Chapter 1 Introduction

3 1-1 DATA COMMUNICATIONS The term telecommunication means communication at a distance. The word data refers to information presented in whatever form is agreed upon by the parties creating and using the data. Data communications are the exchange of data between two devices via some form of transmission medium such as a wire cable.

4 Communications Model 4

5 Communications Model (Cont.) The fundamental purpose of a communications system is the exchange of data between two parties. The previous Figure introduces a simple model of communication. The key elements of this model are: Source - generates data to be transmitted Transmitter - converts data into transmittable signals Transmission System - carries data from source to destination Receiver - converts received signal into data Destination - takes incoming data 5

6 Communications Tasks Transmission system utilization Addressing Interfacing Signal generation Synchronization Exchange management Error detection and correction Routing Recovery Message formatting Security Network management Flow control 6

7 Communications Tasks (Cont.) The previous Table lists a selection of the key tasks that must be performed in a data communications system: transmission system utilization - need to make efficient use of transmission facilities typically shared among a number of communicating devices. a device must interface with the transmission system once an interface is established, signal generation is required for communication. there must be synchronization between transmitter and receiver, to determine when a signal begins to arrive and when it ends. 7

8 Communications Tasks (Cont.) Error detection and correction are required in circumstances where errors cannot be tolerated. Message formatting has to do with an agreement between two parties as to the form of the data to be exchanged or transmitted. Frequently need to provide some measure of security in a data communications system. 8

9 Communications Tasks (Cont.) Flow control is required to assure that the source does not overwhelm the destination by sending data faster than they can be processed and absorbed. addressing and routing, so a source system can indicate the identity of the intended destination, and can choose a specific route through this network. Recovery allows an interrupted transaction to resume activity at the point of interruption or to condition prior to the beginning of the exchange 9

10 Communications Tasks (Cont.) there is a variety of requirements for communication between two parties that might be collected under the term exchange management. Network management capabilities are needed to configure the system, monitor its status, react to failures and overloads, and plan intelligently for future growth. 10

11 Data Communications Model 11

The business manager is concerned with a facility providing the

12 Transmission Lines The basic building block of any communications facility is the transmission line. The business manager is concerned with a facility providing the required capacity, with acceptable reliability, at minimum cost. Transmission Line Facilities Capacity Reliability Cost 12

13 Two mediums currently driving the evolution of data communications transmission are: and 13

allowing equipment and networks to deal simultaneously

14 Networking Advances in technology have led to greatly increased capacity and the concept of integration, allowing equipment and networks to deal simultaneously with voice, data, image, and even video. Voice Data Image Video 14

15 Trends challenging data communications traffic growth development of new services advances in technology 15

16 Main Components of data communication Sender, Receiver, Message, Protocol, Medium Five components of data communication 16

17 Figure 2: Data flow (simplex, half-duplex, and full-duplex) 17

18 Key Network Terminology Explained (3) Simplex: information flows in only one direction Half-duplex: information flows in two directions, but only in one direction at a time. Full-duplex: information flows in two directions at the same time 18

19 Half duplex Listen before you transmit Listen while you transmit If there is a collision, both transmitters will: Jam Re-try sending the packet Minimal packet size: 64 bytes 19

20 Full duplex Allows transmission/reception simultaneously Impossible on older coax media Easy to implement on twisted pair/fiber media No collisions More bandwidth available 20

21 NETWORKS A network is a set of devices (often referred to as nodes) connected by communication links. A node can be a computer, printer, or any other device capable of sending and/or receiving data generated by other nodes on the network. 21

22 A Network Example 22

23 CONNECTION TYPES There are two types of connections: point-to-point multipoint Figure 3: Types of connections: point-to-point and multipoint 23

24 Why Do We Use Networks? Efficiency Necessity Convenience (suitable for our purposes and needs) Networks allow the transfer of Files Data Shared applications 24

25 Why Do We Use Networks? (continued) Networks allow computers and users to share Printers Scanners Fax Machines Processors Disk drives Many other resources 25

26 References 1. Data and Computer Communications, Ninth Edition by William Stallings, (c) Pearson Education - Prentice Hall, Data Communication and Networking, Fourth Edition by Behrouz A. Forouzan, McGraw- Hill 26

Data and Computer Communications Chapter 1 Data Communications, Data Networks, and the Internet

Data and Computer Communications Chapter 1 Data Communications, Data Networks, and the Internet Ninth Edition by William Stallings Data and Computer Communications, Ninth Edition by William Stallings,