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CPE400/ECG600 Fall 2013 1

DATA AND COMPUTER COMMUNICATIONS

Mei Yang

Based on Lecture slides by William Stallings

Lecture 1 Overview -Data Communications, Data Networks, and the Internet

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OUTLINE

Data Communications and Networking for Today’s EnterpriseA Communications ModelData CommunicationsNetworksThe Internet

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DATA COMMUNICATIONS ANDNETWORKING FOR TODAY’S ENTERPRISE

TrendsThree forces that drive the architecture and evolution of data communications and networking

•Development of new services

•Advances in technology

Traffic growth

at a high & steady

rate3

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TECHNOLOGY TRENDS

Four technology trends are particularly notable:

The trend toward faster and cheaper, both in computing and communications, continuesBoth voice-oriented telecommunications networks and data networks are more “intelligent” than everThe Internet, the Web, and associated applications have emerged as dominant features of both business and personal worldThere have been a trend toward ever-increasing mobility for decades

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TECHNOLOGY TRENDS (CONT’D)

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SIGNIFICANT CHANGES INREQUIREMENTS

Emergence of high-speed LANsExamples: centralized server farms, power workgroups, and high-speed local backbone

Corporate WAN needsDriven by the needs of centralized data processing model and distribution of multiple offices.

Digital electronics

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CONVERGENCE

The merger of previously distinct telephony and information technologies and marketsLayers:• applications

these are seen by the end users• enterprise services

services the information network supplies to support applications

• infrastructurecommunication links available to the enterprise

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CONVERGENCE LAYERS

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BENEFITS

Efficiency

• better use of existing resources, and implementation of centralized capacity planning, asset and policy management

Effectiveness

• the converged environment provides users with flexibility, rapid standardized service deployment and enhanced remote connectivity and mobility

Transformation

• enables the enterprise-wide adoption of global standards and associated service levels

Convergence benefits include:

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A COMMUNICATIONS MODEL

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COMMUNICATIONS TASKS

Transmission system utilization Addressing

Interfacing Routing

Signal generation Recovery

Synchronization Message formatting

Exchange management Security

Error detection and correction Network management

Flow control 12

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DATA COMMUNICATIONS MODEL

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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.

Capacity

TransmissionLine

Transmission Lines

Reliability

Cost

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TRANSMISSION MEDIUM

selection is a basic choiceinternal use entirely up to businesslong-distance links made by carrier

rapid technology advances change mixfiber optic

wireless

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NETWORKING

growth of number & power of computers is driving need for interconnectionalso seeing rapid integration of voice, data, image & video technologiestwo broad categories of communications networks:

Local Area Network (LAN)Wide Area Network (WAN)

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WIDE AREA NETWORKS

span a large geographical areacross public rights of wayrely in part on common carrier circuitsalternative technologies used include:

leased linecircuit switchingpacket switching: X.25, frame relayAsynchronous Transfer Mode (ATM)

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CIRCUIT SWITCHING

uses a dedicated communications path established for duration of conversationcomprising a sequence of physical linkswith a dedicated logical channele.g. telephone network

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PACKET SWITCHING

data sent out in sequence of small chunks (packets)packets passed from node to node between source and destinationused for terminal to computer and computer to computer communications

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FRAME RELAY

Motivationpacket switching systems have large overheads to compensate for errorsmodern systems are more reliable, errors can be caught in end system

Frame Relay provides higher speeds with most error control overhead removed, up to 2Mbps

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ASYNCHRONOUS TRANSFER MODE

evolution of frame relay and circuit switching

fixed packet (called cell) length via virtual channelswith little overhead for error controlbandwidth from 10Mbps to Gbpsconstant data rate using packet switching technique with multiple virtual circuits

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LOCAL AREA NETWORKS (LAN)

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METROPOLITAN AREA NETWORKS (MAN)

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THE INTERNETInternet evolved from ARPANET

first operational packet networkapplied to tactical radio & satellite nets alsohad a need for interoperabilityled to standardized TCP/IP protocols

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INTERNET ELEMENTS

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INTERNET ARCHITECTURE

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EXAMPLE CONFIGURATION

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SUMMARYTrends challenging data communications:

traffic growthdevelopment of new servicesadvances in technology

Transmission mediumsfiber opticwireless

Network categories:WANLAN

Internetevolved from the ARPANETTCP/IP foundation

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