William Stallings Data and Computer Communications 7 th Edition Chapter 1 Data Communications and Networks Overview

What is data communication? Not to be confused with telecommunication— —Any process that permits the passage from a sender to one or more receivers of information of any nature, delivered in any easy to use form by any electromagnetic system. Data communication- —Defined as a subset of telecommunication involving the transmission of data to and from computers and components of computer systems. More specifically data communication is transmitted via mediums such as wires, coaxial cables, fiber optics, or radiated electromagnetic waves such as broadcast radio, infrared light, microwaves, and satellites.

Telecom Channels Channels - the links by which data or voice are transmitted between sending and receiving devices in a network —twisted wires —coaxial cable —fiber-optic cable —backbone —wireless microwave satellite

Copyright 2007 John Wiley & Sons, Inc Datacom Basics Broadband Communications Telecommunications = Transmission of voice, video, and/or data - Implies longer distances - Broad term Data Communications = Movement of computer information by means of electrical or optical transmission systems convergence

Copyright 2007 John Wiley & Sons, Inc Print Server Web Server File Server Printer HUB Router Client Computers To other networks (e.g., Internet) Components of a Local Area Network Servers Circuits

Copyright 2007 John Wiley & Sons, Inc Intranet vs. Extranet Intranet —A LAN that uses the Internet technologies within an organization —Open only those inside the organization —Example: insurance related information provided to employees over an intranet(my account/personal account) Extranet( your portal login) —A LAN that uses the Internet technologies across an organization including some external constituents —Open only those invited users outside the organization —Accessible through the Internet —Example: Suppliers and customers accessing inventory information in a company over an extranet

A Communications Model Source —generates data to be transmitted Transmitter —Converts data into transmittable signals Transmission System —Carries data Receiver —Converts received signal into data Destination —Takes incoming data

Simplified Communications Model - Diagram

Moving Bits through the Network

Putting It all Together Data Communications Supports Applications The Operating System manages the resources of the computer. There must however, be a system that provides a bridge between applications and the devices so they can communicate—this is called a Transaction Control Process (TCP)

Communications Tasks Transmission system utilizationAddressing InterfacingRouting Signal generationRecovery SynchronizationMessage formatting Exchange managementSecurity Error detection and correctionNetwork management Flow control

Data Communication Frameworks Two major data communication frameworks have been developed to help ensure that networks meet business and communication requirements: —Open Systems Interconnection (OSI) reference model developed by the International Standards Organization (ISO) —Transmission Control Protocol/Internet Protocol (TCP/IP) suite

Copyright 2007 John Wiley & Sons, Inc Layered Implementation of Communications Functions Applications OS Applications OS Multi layer implementation -Breaking down into smaller components -Easier to implement Single layer implementation -Networking with large components is complex to understand and implement Applications OS Communication Applications OS Communication

Copyright 2007 John Wiley & Sons, Inc Layer Model of OSI Application Layer —set of utilities used by application programs Presentation Layer —formats data for presentation to the user —provides data interfaces, data compression and translation between different data formats Session Layer —initiates, maintains and terminates each logical session between sender and receiver “Please Do Not Touch Steve’s Pet Alligators” Physical DataLink Network Transport Session Presentation Application

Copyright 2007 John Wiley & Sons, Inc Layer Model of OSI Transport Layer —deals with end-to-end issues such as segmenting the message for network transport, and maintaining the logical connections between sender and receiver Network Layer —responsible for making routing decisions Data Link Layer —deals with message, error control and network medium access control Physical Layer —defines how individual bits are formatted to be transmitted through the network

Copyright 2007 John Wiley & Sons, Inc Message Transmission Using Layers Applications senderreceiver A receiving layer wraps incoming message with an envelope Adds layer related addressing information A receiving layer removes the layer related envelope and forwards the message up

Copyright 2007 John Wiley & Sons, Inc Message Transmission Example

Networking Point to point communication not usually practical —Devices are too far apart —Large set of devices would need impractical number of connections Solution is a communications network —Wide Area Network (WAN) —Local Area Network (LAN)

Wide Area Networks Large geographical area

HUB/ROUTER/SWITCHES:

A hub is basically the same as a repeater, but the hub will have more ports HUB:

Switch: The switch will typically buffer and queue packets

Router: A device that forwards data packets between computer networks,data packetscomputer networks

Local Area Networks Smaller scope —Building or small campus Data rates much higher

LAN Configurations Switched —Switched Ethernet May be single or multiple switches —ATM LAN The ATM switch handles transmission of cells through the ATM network. —Fibre Channel Wireless —Mobility —Ease of installation

Networking Configuration: Switch/Router

Networking Configuration: ATM

Optical LAN High bandwidth (1Gbps and up) stronger, lighter, smaller than comparable copper cable, durable Faster Higher Security.

Optical LAN

Wireless LAN

Network Topology: Describes the shape of a network and how computers are interconnected. Types of Network Topology: 1.Ring Topology 2.Star Topology 3.Bus Topology

Ring Topology: Connected user goes from one computer to the other. no central equipment necessary. A failure in any cable or device breaks the loop and can take down the entire network.

Star Topology: Each computer has a separate connection to the central component hub or switch. failure in any star network cable will only take down one computer's network access and not the entire LAN.

Bus Topology: features a common backbone to connect all devices. Failure of one of the station does not affect others.

Networking Topology: