chapter 13 communication protocols information technology in theory by pelin aksoy and laura...

Chapter 13Communication Protocols

Information Technology in Theory

By Pelin Aksoy and Laura DeNardis

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Objectives

• Understand the purpose and importance of communication protocols

• Gain familiarity with the seven-layer OSI reference model

• Learn about TCP/IP, the protocols that enable communications over the Internet


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Objectives (continued)

• Understand the role of standards organizations in the development of protocols

• Identify the economic and political implications of IT standards


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The Need for Protocols

• Computers and communication devices can seamlessly share and exchange information only if they “speak the same language,” adhering to a common system of rules known as protocols

• To understand how and why computers use protocols, consider how people rely on protocols in everyday life


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Protocols in Real Life


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The Role of Protocols

• Formatting information in binary code• Breaking up information into manageable units

prior to transmission (these units include packets, frames, and cells, as discussed in the previous chapter)

• Detecting the presence of another node on the network


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The Role of Protocols (continued)

• Specifying what kind of standard connector an Ethernet cable should have

• Initiating or terminating a connection• Appending a source and destination address to the

bits in a standardized format• Applying error detection and correction methods

(for example, adding a parity bit)


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The Role of Protocols (continued)


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Protocol Suites

• With so many protocols simultaneously acting on the same information, it can be challenging to understand their individual responsibilities

• A taxonomic approach of grouping protocols into families, called network protocol suites, is useful

• Protocols are hierarchical, in that any given protocol depends on or builds upon protocols that have already been applied

• Protocols are divided into “layers,” with each layer defining a specific function


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The OSI Reference Model

• Helps organize, discuss, and understand the many functions required to exchange information between computing devices

• Developed in the 1980s by the International Organization for Standardization (ISO)

• Divides protocol functions into seven categories, or layers


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The OSI Reference Model (continued)


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Layer 1: Physical Layer

• Specifies the functions of protocols that define the electrical and mechanical specifications for the interface between a device and a transmission medium, such as fiber-optic cable, coaxial cable, or twisted pair

• Voltage levels, transmission rates, signal timing, connection specifications, and other characteristics are addressed at this layer

• Example: TIA/EIA-232 serial interface


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Layer 1: Physical Layer (continued)

TIA/EIA-232 9-pin interface


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Layer 1: Physical Layer (continued)

TIA/EIA-232 9-pin specificationInformation Technology in Theory

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Layer 2: Data Link Layer

• Some Data Link layer specifications define physical addressing, such as Ethernet addresses for a network interface card that connects a computing device to a local area network

• Other important network functions at this layer include topology (such as ring or bus) and frame formats

• Closely associated with specific LAN standards, e.g., Ethernet and some WAN standards like frame relay


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Layer 2: Data Link Layer (continued)

Network interface card


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Layer 2: Data Link Layer (continued)

Standard frame relay frame structure


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Layer 3: Network Layer

• Responsible for how packets should be routed and switched through a network

• Handles the logical (software-defined) global network address of the sender and destination

• Specifications defined at this layer are critical for the successful functioning of routers

• One of the best-known network protocols operating at this layer is the Internet Protocol (IP)


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Layer 3: Network Layer (continued)

Network routerInformation Technology in Theory

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Layer 3: Network Layer (continued)


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Layer 4: Transport Layer

• Ensures that information has successfully moved between two points on a network

• Segments data for transmission over a network and ensures that data arrives at its destination in the proper order

• Performs error detection and correction• e.g. TCP and UDP


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Layer 4: Transport Layer (continued)


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Layer 5: Session Layer

• Protocols that establish, maintain, and terminate sessions between two computing devices that are exchanging information

• The term session refers to the logical connection between two devices from the establishment of the connection to the termination of the session

• Some examples of real-world Session layer protocols are Remote Procedure Call (RPC) and H.323, a protocol that provides audio and video sessions over a packet network


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Layer 6: Presentation Layer

• Formats and encodes information from an application so that other computing devices using the same standard will understand it

• The Presentation layer is aptly named because it is responsible for the presentation of information

• Standards at this layer convert data to standard formats and also provide important roles such as compressing information or applying encryption

• e.g. MPEG, ASCII, JPEG


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Layer 6: Presentation Layer (continued)

Segment of the ASCII table


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Layer 7: Application Layer

• A user interacts with a network primarily through applications running on a computer

• These applications, in turn, interact with Application layer protocols that initiate the communications process and coordinate the exchange of information between two networked devices

• An example of a protocol that operates at the Application layer is HTTP


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Layer 7: Application Layer (continued)

URL specifying the HTTP protocol


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The TCP/IP Protocol Suite

• Universal protocols for information exchange between computers and associated devices over the Internet

• To communicate over the Internet, a computing device must “speak” TCP/IP

• By strict definition, TCP/IP is two protocols: TCP (Transmission Control Protocol) and IP (Internet Protocol)


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The TCP/IP Protocol Suite (continued)

• TCP/IP customarily describes an entire family of protocols known as the TCP/IP protocol suite– e.g. FTP, SMTP, IP

• The protocols of what is usually called the TCP/IP protocol suite group into four layers: – Network Interface layer

– Internet layer

– Transport layer

– Application layer


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The TCP/IP Protocol Suite (continued)


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Putting It All Together• Within a computer, data passes from a software

application, such as a Web browser, to software that implements TCP

• Data is divided into manageable pieces and formats and routines are applied to ensure that data arrives correctly at its destination

• The next step involves the Internet Protocol (IP), which applies information to logically address and route the data to its destination


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Putting It All Together (continued)• An Ethernet protocol or other network interface

protocol may append a physical address of a piece of networking hardware

• The network interface protocol also transforms the data into an appropriate format for a stream of bits to pass physically from a computer to a network

• Depending on the information transmitted, the exchange might also rely on the ASCII standard for formatting text, JPEG for formatting images, or the MP3 standard for formatting and compressing audio


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Organizations That Set Standards

• If protocols are agreed-upon rules, who has to agree?

• Someone has to design, publish, and maintain these network protocols

• No single organization, government, or company assumes responsibility for establishing the enormous number of standards required for network communications


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Organizations That Set Standards (continued)

• A complex matrix of organizations assumes responsibility for setting standards in various areas– National

– International

– Professional organizations

– Consortia of technology companies

– Completely open to public participation


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De Jure and De Facto Standards

• De facto (“from the fact” in Latin) standards – Rise to dominance not through a formal process of

collaborative effort, but are adopted over time by gaining momentum or because they are considered best industry practices

• De jure (“from the law” in Latin) standards – Developed through a formal, premeditated process,

such as a standards-setting organization that collaborates to develop a protocol standard that addresses a specific requirement


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ANSI

• American National Standards Institute• One of the oldest standards institutions in the

world– Founded in 1918

• Private, nonprofit organization with participating members from businesses, organizations, academic institutions, and governmental agencies

• Promotes and coordinates standards that are in the nation’s economic interest


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EIA

• The Electronic Industries Alliance• Trade organization of more than 2500 companies

involved in manufacturing electronic systems and components

• Specifies electrical standards for a variety of networking components, including TIA/EIA-232 connectors and Category 6 cable under TIA/EIA-568-B.2-1


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ISO

• International Organization for Standardization• International standards-setting organization• Made up of national standards bodies from more

than 150 countries


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IEEE

• Institute of Electrical and Electronics Engineers• Nonprofit professional organization of engineers• Important IEEE specifications include Ethernet,

token ring, and wireless LAN standards


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IETF

• Internet Engineering Task Force• Group most directly responsible for developing

Internet protocol standards• Has no formal membership, but has more than 100

“working groups” that advance Internet standards • Since 1969, an electronically published archive

known as the “request for comments,” or RFC series, has documented the Internet standards process


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ITU

• International Telecommunication Union• International telecommunications standards

organization operating under the auspices of the United Nations


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W3C

• World Wide Web Consortium• Founded in 1994 with the mission of promoting

continued development of Web technologies and ensuring interoperable, vendor-independent Web standards


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NIST

• National Institute of Standards and Technology • United States• Dates back to 1901


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Economics & Politics of Protocols

• Protocols are often invisible to users• Protocols sometimes thought of as “just a

technical design decision”

• Because protocols represent a source of control over technology, they can serve as a site of economic competition and political influence


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Protocols and the Public Interest

• Some standards design decisions establish public policy

• For example, encryption protocols exist in tension between law enforcement and privacy

• Standards are set usually by private companies• Who should be involved in setting standards that

establish public policy?


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Economic Implications of Protocols

• Having influence over the outcome of standards selections can produce great economic advantages

• Innovation• Intellectual property• National economic competitiveness• Barriers to trade


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Summary• Computing devices can exchange information over

a network if they adhere to standard rules called protocols

• Protocols perform a number of functions, including how to format information in binary code, how to indicate the initiation or termination of a connection, and how to append standard addressing information prior to transmission

• The OSI reference model is a framework that groups the many protocols and protocol functions required to exchange information over a network


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Summary (continued)

• The TCP/IP protocol suite is the group of communications protocols that exchange over the public Internet (and private TCP/IP networks)

• Many standards-setting organizations establish communication protocols; organizations work for companies that have a stake in the outcome of protocol design and include ANSI, EIA, NIST, the IEEE, the IETF, the ITU, the ISO, and the W3C


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Summary (continued)

• Protocols have economic implications because they represent a means of control over competing equipment and software manufacturers, determine how innovative markets can be, and sometimes even serve as barriers to trade in global IT markets


chapter 13 communication protocols information technology in theory by pelin aksoy and laura...

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theoryinformation technology

networkinformation technology

layersinformation technology

internetinformation

functions of protocols

useful protocols

exchange information

layer osi reference