Connectionless protocols are used because they are often more efficient, as the data being transmitted usually do not justify the extra overhead required by

connection-oriented protocols.

Data acknowledgment Data transmitted

Setup response Setup request

Connection clear request NETWORK Station 1 Station 2 Clear response (a) Data Data Data Data Data (b) NETWORK Station 1 Station 2

FIGURE 1 Network protocols: (a) connection-oriented; (b) connectionless

3-2-2 Syntax and semantics. Protocols include the concepts of syntax and se-

mantics. Syntax refers to the structure or format of the data within the message, which in-

cludes the sequence in which the data are sent. For example, the first byte of a message might be the address of the source and the second byte the address of the destination. Se- mantics refers to the meaning of each section of data. For example, does a destination ad- dress identify only the location of the final destination, or does it also identify the route the data takes between the sending and receiving locations?

3-3 Data Communications Standards

During the past several decades, the data communications industry has grown at an astro- nomical rate. Consequently, the need to provide communications between dissimilar com- puter equipment and systems has also increased. A major issue facing the data communi- cations industry today is worldwide compatibility. Major areas of interest are software and programming language, electrical and cable interface, transmission media, communica- tions signal, and format compatibility. Thus, to ensure an orderly transfer of information, it has been necessary to establish standard means of governing the physical, electrical, and procedural arrangements of a data communications system.

A standard is an object or procedure considered by an authority or by general consent as a basis of comparison. Standards are authoritative principles or rules that imply a model or pattern for guidance by comparison. Data communications standards are guidelines that

have been generally accepted by the data communications industry. The guidelines outline procedures and equipment configurations that help ensure an orderly transfer of informa- tion between two or more pieces of data communications equipment or two or more data communications networks. Data communications standards are not laws, however—they are simply suggested ways of implementing procedures and accomplishing results. If everyone complies with the standards, everyone’s equipment, procedures, and processes will be compatible with everyone else’s, and there will be little difficulty communicating information through the system. Today, most companies make their products to comply with standards.

There are two basic types of standards: proprietary (closed) system and open sys- tem. Proprietary standards are generally manufactured and controlled by one company. Other companies are not allowed to manufacture equipment or write software using this standard. An example of a proprietary standard is Apple Macintosh computers. Advan- tages of proprietary standards are tighter control, easier consensus, and a monopoly. Disadvantages include lack of choice for the customers, higher financial investment, overpricing, and reduced customer protection against the manufacturer going out of business.

With open system standards, any company can produce compatible equipment or software; however, often a royalty must be paid to the original company. An example of an open system standard is IBM’s personal computer. Advantages of open system standards are customer choice, compatibility between venders, and competition by smaller compa- nies. Disadvantages include less product control and increased difficulty acquiring agree- ment between vendors for changes or updates. In addition, standard items are not always as compatible as we would like them to be.

4 STANDARDS ORGANIZATIONS FOR DATA COMMUNICATIONS

A consortium of organizations, governments, manufacturers, and users meet on a regular ba- sis to ensure an orderly flow of information within data communications networks and sys- tems by establishing guidelines and standards. The intent is that all data communications equipment manufacturers and users comply with these standards. Standards organizations generate, control, and administer standards. Often, competing companies will form a joint committee to create a compromised standard that is acceptable to everyone. The most promi- nent organizations relied on in North America to publish standards and make recommenda- tions for the data, telecommunications, and networking industries are shown in Figure 2.

4-1 International Standards Organization (ISO)

Created in 1946, the International Standards Organization (ISO) is the international or- ganization for standardization on a wide range of subjects. The ISO is a voluntary, nontreaty organization whose membership is comprised mainly of members from the standards com- mittees of various governments throughout the world. The ISO creates the sets of rules and standards for graphics and document exchange and provides models for equipment and sys- tem compatibility, quality enhancement, improved productivity, and reduced costs. The ISO is responsible for endorsing and coordinating the work of the other standards organi- zations. The member body of the ISO from the United States is the American National Stan- dards Institute (ANSI).

4-2 International Telecommunications Union— Telecommunications Sector

The International Telecommunications Union—Telecommunications Sector (ITU-T), formerly the Comité Consultatif Internationale de Télégraphie et Téléphonie (CCITT), is one of four per- manent parts of the International Telecommunications Union based in Geneva, Switzerland.

ITU-T IEEE TIA EIA ISO ANSI IETF IAB IRTF

FIGURE 2 Standards organizations for data and network

communications

Membership in the ITU-T consists of government authorities and representatives from many countries. The ITU-T is now the standards organization for the United Nations and develops the recommended sets of rules and standards for telephone and data communications. The ITU-T has developed three sets of specifications: the V series for modem interfacing and data trans- mission over telephone lines; the X series for data transmission over public digital networks, e-mail, and directory services; and the I and Q series for Integrated Services Digital Network (ISDN) and its extension Broadband ISDN (sometimes called the Information Superhighway). The ITU-T is separated into 14 study groups that prepare recommendations on the following topics:

Network and service operation Tariff and accounting principles

Telecommunications management network and network maintenance Protection against electromagnetic environment effects

Outside plant

Data networks and open system communications Characteristics of telematic systems

Television and sound transmission

Language and general software aspects for telecommunications systems Signaling requirements and protocols

End-to-end transmission performance of networks and terminals General network aspects

Transport networks, systems, and equipment Multimedia services and systems

4-3 Institute of Electrical and Electronics Engineers

The Institute of Electrical and Electronics Engineers (IEEE) is an international professional organization founded in the United States and is comprised of electronics, computer, and communications engineers. The IEEE is currently the world’s largest professional society

with over 200,000 members. The IEEE works closely with ANSI to develop communica- tions and information processing standards with the underlying goal of advancing theory, creativity, and product quality in any field associated with electrical engineering.

4-4 American National Standards Institute

The American National Standards Institute (ANSI) is the official standards agency for the United States and is the U.S. voting representative for the ISO. However,ANSI is a completely private, nonprofit organization comprised of equipment manufacturers and users of data pro- cessing equipment and services. Although ANSI has no affiliations with the federal govern- ment of the United States, it serves as the national coordinating institution for voluntary stan- dardization in the United States. ANSI membership is comprised of people from professional societies, industry associations, governmental and regulatory bodies, and consumer groups.

4-5 Electronics Industry Association

The Electronics Industries Associations (EIA) is a nonprofit U.S. trade association that es- tablishes and recommends industrial standards. EIA activities include standards develop- ment, increasing public awareness, and lobbying. The EIA is responsible for developing the RS (recommended standard) series of standards for data and telecommunications.

4-6 Telecommunications Industry Association

The Telecommunications Industry Association (TIA) is the leading trade association in the communications and information technology industry. The TIA facilitates business devel- opment opportunities and a competitive marketplace through market development, trade promotion, trade shows, domestic and international advocacy, and standards development. The TIA represents manufacturers of communications and information technology prod- ucts and services providers for the global marketplace through its core competencies. The TIA also facilitates the convergence of new communications networks while working for a competitive and innovative market environment.

4-7 Internet Architecture Board

In 1957, the Advanced Research Projects Agency (ARPA), the research arm of the Department of Defense, was created in response to the Soviet Union’s launching of Sputnik. The original purpose ofARPA was to accelerate the advancement of technologies that could possibly be use- ful to the U.S. military. When ARPANET was initiated in the late 1970s, ARPA formed a com- mittee to oversee it. In 1983, the name of the committee was changed to the Internet Activities

Board (IAB). The meaning of the acronym was later changed to the Internet Architecture Board.

Today the IAB is a technical advisory group of the Internet Society with the follow- ing responsibilities: