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Overview of Data Communicationsand

Networking

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The termtelecommunication means communication at a distance. The worddata refers to information presented in whatever form is agreed upon by theparties creating and using the data. Data communications are the exchangeof data between two devices via some form of transmission medium such asa wire cable.

1-1 DATA COMMUNICATIONS

Topics discussed in this section:

ComponentsData Representation

Data Flow

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Figure 1.1 Five components of data communication

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Figure 1.2 Data flow (simplex, half-duplex, and full-duplex)

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1-2 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 receivingdata generated by other nodes on the network.

Distributed ProcessingNetwork Criteria

Physical Structures

Network Models

Categories of NetworksInterconnection of Networks: Internetwork

Topics discussed in this section:

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Figure 1.3 Types of connections: point-to-point and multipoint

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Figure 1.4 Categories of topology

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Categories of networks

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MAN

An isolated LAN connecting 12computers to a hub in a closet

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Figure 1.11 WANs: a switched WAN and a point-to-point WAN

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1-3 THE INTERNET

The Internet hasrevolutionized manyaspects of our daily lives.It has affected the way wedo business as well as theway we spend our leisure

time. The Internet is acommunication systemthat has brought a wealthof information to ourfingertips and organized it

for our use.

Internet today

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Figure 1.12 A heterogeneous network made of four WANs and two LANs

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Figure 1.13 Hierarchical organization of the Internet

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1-4 PROTOCOLS AND STANDARDS

Protocols

First, we define protocol, which is synonymous with ruleStandards

which are agreed-upon rules.

Why standards?

Required to allow for interoperability between equipmentAdvantages

Ensures a large market for equipment and software Allows products from different vendors to communicate

DisadvantagesFreeze technology May be multiple standards for the same thing

Defacto and Dejure standards

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Key Organizations

Standards organizations provide forums for discussion, help

turn discussion into formal specifications Most standards organizations have specific processes for

turning ideas into formal standards.

They all iterate through several rounds of organizing ideas,

discussing the ideas, developing draft standards, voting on allor certain aspects of the standards, and finally formally

releasing the completed standard to the public.

Some of the better-known standards organizations follow:

International Organization for Standardization (ISO)An internationalstandards organization responsible for a wide range of standards, including

those relevant to networking. This organization is responsible for the OSI

reference model and the OSI protocol suite.

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Key Organizations (cont)

American National Standards Institute (ANSI)The coordinating body forvoluntary standards groups within the United States. ANSI is a member of

ISO. ANSIs best-known communications standard is FDDI.

Electronic Industries Association (EIA)A group that specifies electricaltransmission standards. EIAs best-known standard is EIA/TIA-232

(formerly RS-232).

Institute of Electrical and Electronic Engineers (IEEE)A professionalorganization that defines:

Network standards. IEEE LAN standards (including IEEE 802.3 andIEEE 802.5) are the best-known IEEE communications standards and are

the predominant LAN standards in the world today. International Telecommunication Union Telecommunication

Standardization Sector (ITU-T) (formerly the Committee for InternationalTelegraph and Telephone [CCITT])An international organization that

develops communication standards. The best-known ITU-T standard is X.25.

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Key Organizations (cont)

Internet Activities Board (IAB)A group of internetwork researchers whomeet regularly to discuss issues pertinent to the Internet. This board sets much

of the policy for the Internet through decisions and assignment of task forces to

various issues.

Some Request for Comments (RFC) documents are designated by the

IAB as Internet standards, including Transmission Control

Protocol/Internet Protocol(TCP/IP) and the Simple Network

Management Protocol(SNMP).