Chapter 13 Communication Protocols Information Technology in Theory By Pelin Aksoy and Laura DeNardis

2 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 Information Technology in Theory

3 Objectives (continued) Understand the role of standards organizations in the development of protocols Identify the economic and political implications of IT standards Information Technology in Theory

4 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 Information Technology in Theory

5 Protocols in Real Life Information Technology in Theory

6 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 Information Technology in Theory

7 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) Information Technology in Theory

8 The Role of Protocols (continued) Information Technology in Theory

9 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 Information Technology in Theory

10 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 Information Technology in Theory

11 The OSI Reference Model (continued) Information Technology in Theory

12 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 Information Technology in Theory

13 Layer 1: Physical Layer (continued) TIA/EIA pin interface Information Technology in Theory

14 Layer 1: Physical Layer (continued) TIA/EIA pin specification Information Technology in Theory

15 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 Information Technology in Theory

16 Layer 2: Data Link Layer (continued) Network interface card Information Technology in Theory

17 Layer 2: Data Link Layer (continued) Standard frame relay frame structure Information Technology in Theory

18 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) Information Technology in Theory

19 Layer 3: Network Layer (continued) Network router Information Technology in Theory

20 Layer 3: Network Layer (continued) Information Technology in Theory

21 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 Information Technology in Theory

22 Layer 4: Transport Layer (continued) Information Technology in Theory

23 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 Information Technology in Theory

24 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 Information Technology in Theory

25 Layer 6: Presentation Layer (continued) Segment of the ASCII table Information Technology in Theory

26 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 Information Technology in Theory

27 Layer 7: Application Layer (continued) URL specifying the HTTP protocol Information Technology in Theory

28 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) Information Technology in Theory

29 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 Information Technology in Theory

30 The TCP/IP Protocol Suite (continued) Information Technology in Theory

31 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 Information Technology in Theory

32 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 Information Technology in Theory

33 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 Information Technology in Theory

34 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 Information Technology in Theory

35 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 Information Technology in Theory

36 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 Information Technology in Theory

37 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 Information Technology in Theory

38 ISO International Organization for Standardization International standards-setting organization Made up of national standards bodies from more than 150 countries Information Technology in Theory

39 IEEE Institute of Electrical and Electronics Engineers Nonprofit professional organization of engineers Important IEEE specifications include Ethernet, token ring, and wireless LAN standards Information Technology in Theory

40 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 Information Technology in Theory

41 ITU International Telecommunication Union International telecommunications standards organization operating under the auspices of the United Nations Information Technology in Theory

42 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 Information Technology in Theory

43 NIST National Institute of Standards and Technology United States Dates back to 1901 Information Technology in Theory

44 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 Information Technology in Theory

45 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? Information Technology in Theory

46 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 Information Technology in Theory

47 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 Information Technology in Theory

48 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 Information Technology in Theory

49 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 Information Technology in Theory