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PART ONE INTRODUCTION
C H A P T E R 1
INTRODUCTION TO DATA
COMMUNICATIONS
This chapter introduces the basic concepts of data communications. It describes why it is impor-
tant to study data communications, how data communications fit within the discipline of Man- agement Information Systems (MIS), and introduces you to the three fundamental questions that this book answers. Next, it discusses the basic types and components of a data communications network. Also, it examines the importance of a network model based on layers. Finally, it describes the three key trends in the future of networking.
OBJECTIVES ◾ Be aware of the three fundamental questions this book answers
◾ Be aware of the applications of data communications networks ◾ Be aware of how data communications fit within the discipline of MIS ◾ Be familiar with the major components of and types of networks ◾ Understand the role of network layers ◾ Be familiar with the role of network standards ◾ Be aware of cyber security issues ◾ Be aware of three key trends in communications and networking
OUTLINE 1.1 Introduction
1.2 Data Communications Networks 1.2.1 Components of a Network 1.2.2 Types of Networks 1.3 Network Models 1.3.1 Open Systems Interconnection Reference Model 1.3.2 Internet Model 1.3.3 Message Transmission Using Layers 1.4 Network Standards
1.4.1 The Importance of Standards 1.4.2 The Standards-Making Process 1.4.3 Common Standards 1.5 Future Trends 1.5.1 Wireless LAN and BYOD 1.5.2 The Internet of Things 1.5.3 Massively Online 1.6 Implications for Cyber Security Summary
1.1 INTRODUCTION
What Internet connection should you use? Cable modem or DSL (formally called Digital Sub- scriber Line)? Cable modems are supposedly faster than DSL, providing data speeds of 50 Mbps to DSL’s 1.5–25 Mbps (million bits per second). One cable company used a tortoise to represent DSL in advertisements. So which is faster? We’ll give you a hint. Which won the race in the fable, the tortoise or the hare? By the time you finish this book, you’ll understand which is faster and why, as well as why choosing the right company as your Internet service provider (ISP) is probably more important than choosing the right technology.
1
COPYRIGHTED MATERIAL
2 Chapter 1 Introduction to Data Communications
Over the past decade or so, it has become clear that the world has changed forever due to the third and fourth Industrial Revolutions. The first Industrial Revolution revolutionized the way people worked at the end of the 18th century by introducing machines, steam and water power. New companies and industries emerged, and old ones died off. The second Industrial Revolution in the late 19th century is known for starting mass production, electricity, and the telephone. The third Industrial Revolution, in the second half of the 20th century, is revolutionizing the way people work through electronics and information technology (IT) to automate production. The fourth Industrial Revolution is currently underway. It builds on the technological advances of the third Industrial Revolution, but the way it merges the physical, digital, and bio- logical worlds is unprecedented. It is deeply rooted in the Internet and digitization. Digitization enables us to build a world where interactions can happen in real time across different continents (think about email, instant messaging, and exchange of data between different devices). These interactions are possible because of technologies such as cloud, big data, big data analytics, and the Internet of Things. But the technology that enables all these technologies to communicate is the high-speed data communication network, that is, the Internet. Today, the value of a high-speed data communications network is that it brings people together in a way never before possible. In the 1800s, it took several weeks for a message to reach North America by ship from England. By the 1900s, it could be transmitted within an hour. Today, it can be transmitted in seconds. Collapsing the information lag to Internet speeds means that peo- ple can communicate and access information anywhere in the world regardless of their physical location. In fact, today’s problem is that we cannot handle the quantities of information we receive. Data communications and networking is a truly global area of study, both because the technology enables global communication and because new technologies and applications often emerge from a variety of countries and spread rapidly around the world. The World Wide Web, for example, was born in a Swiss research lab, was nurtured through its first years primarily by European universities and exploded into mainstream popular culture because of a development at an American research lab. One of the problems in studying a global phenomenon lies in explaining the different polit- ical and regulatory issues that have evolved and currently exist in different parts of the world. Rather than attempt to explain the different paths taken by different countries, we have chosen simplicity instead. Historically, the majority of readers of previous editions of this book have come from North America. Therefore, although we retain a global focus on technology and its business implications, we focus mostly on North America. This book answers three fundamental questions. First, how does the Internet work? When you access a website using your computer, laptop, iPad, or smartphone, what happens so that the page opens in your Web browser? This is the focus in Chapters 1–5. The short answer is that the software on your computer (or any device) creates a message composed in different software languages (HTTP, TCP/IP, and Ethernet are common) that requests the page you clicked. This message is then broken up into a series of smaller parts that we call packets. Each packet is transmitted to the nearest router, which is a special-purpose computer whose primary job is to find the best route for these packets to their final destination. The packets move from router to router over the Internet until they reach the Web server, which puts the packets back together into the same message that your computer created. The Web server reads your request and then sends the page back to you in the same way—by composing a message using HTTP, TCP/IP, and Ethernet and then sending it as a series of smaller packets back through the Internet that the software on your computer puts together into the page you requested. You might have heard a news story that the U.S. or Chinese government can read your email or see what websites you’re visiting. A more shocking truth is that the person sitting next you at a coffee shop might be doing exactly the same thing—reading all the packets that come from or go to your laptop. How is this possible, you ask? After finishing Chapter 5, you will know exactly how this is possible.
4 Chapter 1 Introduction to Data Communications
FIGURE 1-
What is MIS? IT Strategy
Storing and Retrieving Data
Automating Data Operations
Data Communications and Networking
- Clients and Servers
- Network technologies
- Network security and management
Analyzing and Visualizing Data
Protecting Data
In order for the IT strategy to implement the core capabilities, data communications and networking infrastructure must be available. You are using this infrastructure anytime you use the Internet on your laptop and even your cell phone. MIS core capabilities and the IT strategy rest on a solid infrastructure (see Figure 1-1). Therefore, understanding how data communications
MANAGEMENT
FOCUS
1-1 Career Opportunities
I t’s a great time to be in information technology (IT)! The technology-fueled new economy has dramatically increased the demand for skilled IT professionals. Accord- ing to the U.S. Bureau of Labor Statistics and Career Profiles (http://www.careerprofiles.info), 2 out of 10 fastest growing occupations are computer network administrator and computer systems analyst, which is expected to grow by 22% over the next 10 years with an annual median salary of $72,500—not counting bonuses. There are two reasons for this growth. First, companies have to continuously upgrade their networks and thus need skilled employees to support their expanding IT infrastructure. Second, people are spending more time on their mobile devices, and because employers are allowing them to use these personal devices at work (i.e., BYOD, or bring your own device), the network infrastructure has to support the data that flow from these devices as well as to make sure that they don’t pose a security risk. With a few years of experience, there is the possibil- ity to work as an information systems manager, for which the median annual pay is as high as $117,780. An infor- mation systems manager plans, coordinates, and directs
IT-related activities in such a way that they can fully sup- port the goals of any business. Thus, this job requires a good understanding not only of the business but also of the tech- nology so that appropriate and reliable technology can be implemented at a reasonable cost to keep everything oper- ating smoothly and to guard against cybercriminals. Because of the expanding job market for IT and networking-related jobs, certifications become important. Most large vendors of network technologies, such as the Microsoft Corporation and Cisco Systems Inc., provide certification processes (usually a series of courses and formal exams) so that individuals can document their knowledge. Certified network professionals often earn $10,000 to $15,000 more than similarly skilled uncertified professionals—provided that they continue to learn and maintain their certification as new technologies emerge.
Sources: http://jobs.aol.com, “In Demand Careers That Pay $100,00 a Year or More”; www.careerpath.com, “To- day’s 20 Fastest-Growing Occupations”; www.cnn.com, “30 Jobs Needing Most Workers in Next Decade,” http://www.careerprofiles.info/top-careers.html.
Data Communications Networks 5
and networking works will enable you to understand what it takes for a modern organization to stay in business and for you to be able to work and connect with your family and friends. By the time you finish this book, you’ll understand how networks work, how to design net- works, and how to manage networks. You won’t be an expert, but you’ll be ready to enter an organization and have an educated conversation about the role of data communications and net- works or move on to more advanced courses and workshops.
1.2 DATA COMMUNICATIONS NETWORKS
Data communications is the movement of computer information from one point to another by means of electrical or optical transmission systems. Such systems are often called data communi- cations networks. This is in contrast to the broader term telecommunications, which includes the transmission of voice and video (images and graphics) as well as data and usually implies longer distances. In general, data communications networks collect data from personal computers and other devices and transmit those data to a central server that is a more powerful personal com- puter, minicomputer, or mainframe, or they perform the reverse process, or some combination of the two. Data communications networks facilitate more efficient use of computers and improve the day-to-day control of a business by providing faster information flow. They also provide mes- sage transfer services to allow computer users to talk to one another via email, chat, and video streaming.
TECHNICAL
FOCUS
1-1 Internet Domain Names
I nternet address names are strictly controlled; otherwise, someone could add a computer to the Internet that had the same address as another computer. Each address name has two parts, the computer name and its domain. The general format of an Internet address is therefore com- puter.domain. Some computer names have several parts separated by periods, so some addresses have the format computer.computer.computer.domain. For example, the main university Web server at Indiana University (IU) is called www.indiana.edu, whereas the Web server for the Kelley School of Business at IU is www.kelley.indiana.edu. Since the Internet began in the United States, the American address board was the first to assign domain names to indicate types of organizations. Some common U.S. domain names are as follows:
EDU for an educational institution, usually a university COM for a commercial business GOV for a government department or agency MIL for a military unit ORG for a nonprofit organization
As networks in other countries were connected to the Internet, they were assigned their own domain names. Some international domain names are as follows:
CA for Canada AU for Australia UK for the United Kingdom DE for Germany New top-level domains that focus on specific types of businesses continue to be introduced, such as the following:
AERO for aerospace companies MUSEUM for museums NAME for individuals PRO for professionals, such as accountants and lawyers BIZ for businesses Many international domains structure their addresses in much the same way as the United States does. For example, Australia uses EDU to indicate academic institu- tions, so an address such as xyz.edu.au would indicate an Australian university. For a full list of domain names, see www.iana.org/domains /root/db.
Data Communications Networks 7
FIGURE 1-
Network architecture components
Core Layer Campus Backbone Network
Data Center
Distribution Layer Buliding Backbone Network
Access Layer Local Area Network
Common Carrier
Internet Service Provider
Enterprise Edge
Building
Internet Access
e-Commerce Edge
Enterprise Campus Wide Area Network Access
Distribution Layer Buliding Backbone Network
Access Layer Local Area Network
Building
Enterprise Campus
Enterprise Campus
are usually personal computers (often more powerful than the other personal computers on the network) but may be mainframes too. There are three computers that make networks what they are. These are the client, the server, and the router. The client initiates a communication with the server by sending a request to the server. Once the server receives the request, it processes it, and responds with a response. The router makes this connection possible. All three devices are computers, and their hardware is pretty much the same—they have a motherboard with CPU (central processing unit), memory, and some storage space. However, only the client had a screen, keyboard, and mouse. Why? Are the server and router less deserving? No. Their purpose is not to receive an input from the user (keyboard or mouse) or display output (screen) but rather to respond to requests, so they have no need for. Pretty clever, isn’t it! You probably know that a client can have a variety of client operating systems (e.g., Windows, Mac OS, or Linux) and application software (e.g., a web browser, outlook). Likewise, a server can have different operating systems (e.g., Windows, Linux, or z/OS) and application software (e.g., web server software, Exchange). What do you think is the operating system on a router? It turns out that about 90% of routers run Cisco IOS (Inter-operating system) that was specifically created for routers. In fact, Cisco IOS is the second most popular operating system in the world, ahead of Mac and Linux. Interesting, right?
1.2.2 Types of Networks There are many different ways to categorize networks. One of the most common ways is to look at the geographic scope of the network. Figure 1-3 illustrates three types of networks: local area networks (LANs), backbone networks (BNs), and wide area networks (WANs). The distinctions among these are becoming blurry because some network technologies now used in LANs were originally developed for WANs, and vice versa. Any rigid classification of technologies is certain to have exceptions.
8 Chapter 1 Introduction to Data Communications
A local area network (LAN) is a group of computers located in the same general area. A LAN covers a clearly defined small area, such as one floor or work area, a single building, or a group of buildings. The upper-left diagram in Figure 1-3 shows a small LAN located in the records building at the former McClellan Air Force Base in Sacramento. LANs support high-speed data transmission compared with standard telephone circuits, commonly operating 100 million bits per second (100 Mbps). LANs and wireless LANs are discussed in detail in Chapter 6. Most LANs are connected to a backbone network (BN) , a larger, central network connecting several LANs, other BNs, MANs, and WANs. BNs typically span from hundreds of feet to several miles and provide very high-speed data transmission, commonly 100–1,000 Mbps. The second diagram in Figure 1-3 shows a BN that connects the LANs located in several buildings at McClellan Air Force Base. BNs are discussed in detail in Chapter 7. Wide area networks (WANs) connect BNs and MANs (see Figure 1-1). Most organizations do not build their own WANs by laying cable, building microwave towers, or sending up satellites (unless they have unusually heavy data transmission needs or highly specialized requirements, such as those of the Department of Defense). Instead, most organizations lease circuits from IXCs (e.g., AT&T, Sprint) and use those to transmit their data. WAN circuits provided by IXCs come in all types and sizes but typically span hundreds or thousands of miles and provide data transmission rates from 64 Kbps to 10 Gbps. WANs are discussed in detail in Chapter 8. Two other common terms are intranets and extranets. An intranet is a LAN that uses the same technologies as the Internet (e.g., Web servers, Java, HTML [Hypertext Markup Language]) but is open to only those inside the organization. For example, although some pages on a Web server may be open to the public and accessible by anyone on the Internet, some pages may be on an intranet and therefore hidden from those who connect to the Web server from the Internet at large. Sometimes, an intranet is provided by a completely separate Web server hidden from the Internet. The intranet for the Information Systems Department at Indiana University, for example, provides information on faculty expense budgets, class scheduling for future semesters (e.g., room, instructor), and discussion forums. An extranet is similar to an intranet in that it, too, uses the same technologies as the Internet but instead is provided to invited users outside the organization who access it over the Internet. It can provide access to information services, inventories, and other internal organizational databases that are provided only to customers, suppliers, or those who have paid for access. Typically, users are given passwords to gain access, but more sophisticated technologies such as smart cards or special software may also be required. Many universities provide extranets for Web-based courses so that only those students enrolled in the course can access course materials and discussions.
1.3 NETWORK MODELS
There are many ways to describe and analyze data communications networks. All networks pro- vide the same basic functions to transfer a message from sender to receiver, but each network can use different network hardware and software to provide these functions. All of these hardware and software products have to work together to successfully transfer a message. One way to accomplish this is to break the entire set of communications functions into a series of layers , each of which can be defined separately. In this way, vendors can develop software and hardware to provide the functions of each layer separately. The software or hardware can work in any manner and can be easily updated and improved, as long as the interface between that layer and the ones around it remains unchanged. Each piece of hardware and software can then work together in the overall network. There are many different ways in which the network layers can be designed. The two most important network models are the Open Systems Interconnection Reference (OSI) model and the
10 Chapter 1 Introduction to Data Communications
to solve the problems caused by damaged, lost, or duplicate messages so the succeeding layers are shielded from transmission errors. Thus, layer 2 performs error detection and correction. It also decides when a device can transmit so that two computers do not try to transmit at the same time. We say, that data link layer has a local responsibility.
Layer 3: Network Layer The network layer performs routing. It determines the next computer to which the message should be sent, so it can follow the best route through the network and finds the full address for that computer if needed.
Layer 4: Transport Layer The transport layer deals with end-to-end issues, such as procedures for entering and departing from the network. It establishes, maintains, and terminates logical connec- tions for the transfer of data between the original sender and the final destination of the message. It is responsible for breaking a large data transmission into smaller packets (if needed), ensuring that all the packets have been received, eliminating duplicate packets, and performing flow control to ensure that no computer is overwhelmed by the number of messages it receives. Although error control is performed by the data link layer, the transport layer can also perform error checking. Therefore, transport layer has a global responsibility.
Layer 5: Session Layer The session layer is responsible for managing and structuring all sessions. Session initiation must arrange for all the desired and required services between session partici- pants, such as logging on to circuit equipment, transferring files, and performing security checks. Session termination provides an orderly way to end the session, as well as a means to abort a ses- sion prematurely. It may have some redundancy built in to recover from a broken transport (layer
- connection in case of failure. The session layer also handles session accounting so the correct party receives the bill.
Layer 6: Presentation Layer The presentation layer formats the data for presentation to the user. Its job is to accommodate different interfaces on different computers so the application program need not worry about them. It is concerned with displaying, formatting, and editing user inputs and outputs. For example, layer 6 might perform data compression, translation between different data formats, and screen formatting. Any function (except those in layers 1 through 5) that is requested sufficiently often to warrant finding a general solution is placed in the presentation layer, although some of these functions can be performed by separate hardware and software (e.g., encryption).
Layer 7: Application Layer The application layer is the end user’s access to the network. The primary purpose is to provide a set of utilities for application programs. Each user pro- gram determines the set of messages and any action it might take on receipt of a message. Other network-specific applications at this layer include network monitoring and network management.
1.3.2 Internet Model The network model that dominates current hardware and software is a more simple five-layer Internet model. Unlike the OSI model that was developed by formal committees, the Internet model evolved from the work of thousands of people who developed pieces of the Internet. The OSI model is a formal standard that is documented in one standard, but the Internet model has never been formally defined; it has to be interpreted from a number of standards. The two models have very much in common (see Figure 1-4); simply put, the Internet model collapses the top
Network Models 11
three OSI layers into one layer. Because it is clear that the Internet has won the “war,” we use the five-layer Internet model for the rest of this book.
Layer 1: The Physical Layer The physical layer in the Internet model, as in the OSI model, is the physical connection between the sender and receiver. Its role is to transfer a series of electrical, radio, or light signals through the circuit. The physical layer includes all the hardware devices (e.g., computers, modems, and switches) and physical media (e.g., cables and satellites). The physical layer specifies the type of connection and the electrical signals, radio waves, or light pulses that pass through it. Chapter 3 discusses the physical layer in detail.
Layer 2: The Data Link Layer The data link layer is responsible for moving a message from one computer to the next computer in the network path from the sender to the receiver. The data link layer in the Internet model performs the same three functions as the data link layer in the OSI model. First, it controls the physical layer by deciding when to transmit messages over the media. Second, it formats the messages by indicating where they start and end. Third, it detects and may correct any errors that have occurred during transmission. Chapter 4 discusses the data link layer in detail.
Layer 3: The Network Layer The network layer in the Internet model performs the same func- tions as the network layer in the OSI model. First, it performs routing, in that it selects the next computer to which the message should be sent. Second, it can find the address of that computer if it doesn’t already know it. Chapter 5 discusses the network layer in detail.
Layer 4: The Transport Layer The transport layer in the Internet model is very similar to the transport layer in the OSI model. It performs two functions. First, it is responsible for linking the application layer software to the network and establishing end-to-end connections between the sender and receiver when such connections are needed. Second, it is responsible for breaking long messages into several smaller messages to make them easier to transmit and then recombining the smaller messages back into the original larger message at the receiving end. The transport layer can also detect lost messages and request that they be resent. Chapter 5 discusses the transport layer in detail.
Layer 5: Application Layer The application layer is the application software used by the net- work user and includes much of what the OSI model contains in the application, presentation, and session layers. It is the user’s access to the network. By using the application software, the user defines what messages are sent over the network. Because it is the layer that most people under- stand best and because starting at the top sometimes helps people understand better, Chapter 2 begins with the application layer. It discusses the architecture of network applications and several types of network application software and the types of messages they generate.
Groups of Layers The layers in the Internet are often so closely coupled that decisions in one layer impose certain requirements on other layers. The data link layer and the physical layer are closely tied together because the data link layer controls the physical layer in terms of when the physical layer can transmit. Because these two layers are so closely tied together, decisions about the data link layer often drive the decisions about the physical layer. For this reason, some people group the physical and data link layers together and call them the hardware layers. Likewise, the transport and network layers are so closely coupled that sometimes these layers are called the internetwork layers (see Figure 1-4). When you design a network, you often think about the network design
Network Models 13
Application Layer First, the user creates a message at the application layer using a Web browser by clicking on a link (e.g., get the home page at www.somebody.com). The browser translates the user’s message (the click on the Web link) into HTTP. The rules of HTTP define a specific PDU—called an HTTP packet—that all Web browsers must use when they request a Web page. For now, you can think of the HTTP packet as an envelope into which the user’s message (get the Web page) is placed. In the same way that an envelope placed in the mail needs certain information written in certain places (e.g., return address, destination address), so too does the HTTP packet. The Web browser fills in the necessary information in the HTTP packet, drops the user’s request inside the packet, then passes the HTTP packet (containing the Web page request) to the transport layer.
Transport Layer The transport layer on the Internet uses a protocol called TCP (transmission control protocol), and it, too, has its own rules and its own PDUs. TCP is responsible for breaking large files into smaller packets and for opening a connection to the server for the transfer of a large set of packets. The transport layer places the HTTP packet inside a TCP PDU (which is called a TCP segment), fills in the information needed by the TCP segment, and passes the TCP segment (which contains the HTTP packet, which, in turn, contains the message) to the network layer.
Network Layer The network layer on the Internet uses a protocol called IP (Internet Protocol), which has its rules and PDUs. IP selects the next stop on the message’s route through the net- work. It places the TCP segment inside an IP PDU, which is called an IP packet, and passes the IP packet, which contains the TCP segment, which, in turn, contains the HTTP packet, which, in turn, contains the message, to the data link layer.
Data Link Layer If you are connecting to the Internet using a LAN, your data link layer may use a protocol called Ethernet, which also has its own rules and PDUs. The data link layer formats the message with start and stop markers, adds error checks information, places the IP packet inside an Ethernet PDU, which is called an Ethernet frame, and instructs the physical hardware to trans- mit the Ethernet frame, which contains the IP packet, which contains the TCP segment, which contains the HTTP packet, which contains the message.
Physical Layer The physical layer in this case is network cable connecting your computer to the rest of the network. The computer will take the Ethernet frame (complete with the IP packet, the TCP segment, the HTTP packet, and the message) and send it as a series of electrical pulses through your cable to the server. When the server gets the message, this process is performed in reverse. The physical hardware translates the electrical pulses into computer data and passes the message to the data link layer. The data link layer uses the start and stop markers in the Ethernet frame to identify the message. The data link layer checks for errors and, if it discovers one, requests that the message be resent. If a message is received without error, the data link layer will strip off the Ethernet frame and pass the IP packet (which contains the TCP segment, the HTTP packet, and the message) to the network layer. The network layer checks the IP address and, if it is destined for this computer, strips off the IP packet and passes the TCP segment, which contains the HTTP packet and the message, to the transport layer. The transport layer processes the message, strips off the TCP segment, and passes the HTTP packet to the application layer for processing. The application layer (i.e., the Web server) reads the HTTP packet and the message it contains (the request for the Web page) and processes it by generating an HTTP packet containing the Web page you requested. Then the process starts again as the page is sent back to you.
14 Chapter 1 Introduction to Data Communications
The Pros and Cons of Using Layers There are three important points in this example. First, there are many different software packages and many different PDUs that operate at different layers to successfully transfer a message. Networking is in some ways similar to the Russian matryoshka, nested dolls that fit neatly inside each other. This is called encapsulation, because the PDU at a higher level is placed inside the PDU at a lower level so that the lower-level PDU encapsulates the higher-level one. The major advantage of using different software and protocols is that it is easy to develop new software, because all one has to do is write software for one level at a time. The developers of Web applications, for example, do not need to write software to perform error checking or routing, because those are performed by the data link and network layers. Developers can simply assume those functions are performed and just focus on the application layer. Similarly, it is simple to change the software at any level (or add new application protocols), as long as the interface between that layer and the ones around it remains unchanged. Second, it is important to note that for communication to be successful, each layer in one computer must be able to communicate with its matching layer in the other computer. For example, the physical layer connecting the client and server must use the same type of electrical signals to enable each to understand the other (or there must be a device to translate between them). Ensuring that the software used at the different layers is the same as accomplished by using standards. A standard defines a set of rules, called protocols, that explain exactly how hardware and software that conform to the standard are required to operate. Any hardware and software that conform to a standard can communicate with any other hardware and software that conform to the same standard. Without standards, it would be virtually impossible for computers to communicate. Third, the major disadvantage of using a layered network model is that it is somewhat inef- ficient. Because there are several layers, each with its own software and PDUs, sending a mes- sage involves many software programs (one for each protocol) and many PDUs. The PDUs add to the total amount of data that must be sent (thus increasing the time it takes to transmit), and the different software packages increase the processing power needed in computers. Because the protocols are used at different layers and are stacked on top of one another (take another look at Figure 1-5), the set of software used to understand the different protocols is often called a protocol stack.
1.4 NETWORK STANDARDS
1.4.1 The Importance of Standards Standards are necessary in almost every business and public service entity. For example, before 1904, fire hose couplings in the United States were not standard, which meant a fire department in one community could not help in another community. The transmission of electric current was not standardized until the end of the nineteenth century, so customers had to choose between Thomas Edison’s direct current (DC) and George Westinghouse’s alternating current (AC). The primary reason for standards is to ensure that hardware and software produced by dif- ferent vendors can work together. Without networking standards, it would be difficult—if not impossible—to develop networks that easily share information. Standards also mean that cus- tomers are not locked into one vendor. They can buy hardware and software from any vendor whose equipment meets the standard. In this way, standards help to promote more competition and hold down prices.
16 Chapter 1 Introduction to Data Communications
MANAGEMENT
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1-2 How Network Protocols Become Standards
T here are many standards organizations around the world, but perhaps the best known is the Internet Engineering Task Force (IETF). IETF sets the standards that govern how much of the Internet operates. The IETF, like all standards organizations, tries to seek consensus among those involved before issuing a standard. Usually, a standard begins as a protocol (i.e., a language or set of rules for operating) developed by a vendor (e.g., HTML). When a protocol is proposed for standardization, the IETF forms a working group of technical experts to study it. The working group examines the protocol to identify potential problems and possible extensions and improve- ments, and then issues a report to the IETF. If the report is favorable, the IETF issues a Request for Comment (RFC) that describes the proposed standard and solicits comments from the entire world. Most large software companies likely to be affected by the proposed standard prepare detailed responses. Many “regular” Inter- net users also send their comments to the IETF. The IETF reviews the comments and possibly issues a new and improved RFC, which again is posted for more comments. Once no additional changes have been identi- fied, it becomes a proposed standard.
Usually, several vendors adopt the proposed standard and develop products based on it. Once at least two ven- dors have developed hardware or software based on it and it has proven successful in operation, the proposed stan- dard is changed to a draft standard. This is usually the final specification, although some protocols have been elevated to Internet standards, which usually signifies mature stan- dards not likely to change. The process does not focus solely on technical issues; almost 90% of the IETF’s participants work for manufactur- ers and vendors, so market forces and politics often com- plicate matters. One former IETF chairperson who worked for a hardware manufacturer has been accused of trying to delay the standards process until his company had a prod- uct ready, although he and other IETF members deny this. Likewise, former IETF directors have complained that mem- bers try to standardize every product their firms produce, leading to a proliferation of standards, only a few of which are truly useful.
Sources: “How Networking Protocols Become Standards,” PC Week , March 17, 1997; “Growing Pains,” Network World , April 14, 1997.
MANAGEMENT
FOCUS
1-3 Keeping Up with Technology
T he data communications and networking arena changes rapidly. Significant new technologies are introduced and new concepts are developed almost every year. It is there- fore important for network managers to keep up with these changes. There are at least three useful ways to keep up with change. First and foremost for users of this book is the website for this book, which contains updates to the book, additional sections, teaching materials, and links to useful websites.
Second, there are literally hundreds of thousands of websites with data communications and networking information. Search engines can help you find them. A good initial starting point is the telecom glossary at http://www.atis.org. Three other useful sites are http:// www.zdnet.com, http://www.networkcomputing.com, and http://www.zdnet.com. Third, there are many useful magazines that discuss computer technology in general and networking tech- nology in particular, including Network Computing, Info World, Info Week , and CIO Magazine.
Network Standards 17
FIGURE 1-
Some common data communications stan- dards. HTML = Hyper- text Markup Language; HTTP = Hypertext Transfer Protocol; IMAP = Internet Mes- sage Access Protocol; IP = Internet Protocol; LAN = Local Area Net- work; MPEG = Motion Picture Experts Group; POP = Post Office Pr- otocol; TCP = Trans- mission Control Protocol
Layer Common Standards
**5. Application layer
- Physical layer**
HTTP, HTML (Web) MPEG, H.323 (audio/video) SMTP, IMAP, POP (email)
RS-232C cable (LAN) Category 5 cable (LAN) V.92 (56 Kbps modem)
**4. Transport layer TCP (Internet and LANs)
- Network layer IP (Internet and LANs)
- Data link layer Ethernet (LAN)** Frame relay (WAN) T1 (MAN and WAN)
Institute of Electrical and Electronics Engineers The Institute of Electrical and Electronics Engineers (IEEE) is a professional society in the United States whose Standards Association (IEEE-SA) develops standards (see www.standards.ieee.org). The IEEE-SA is probably most known for its standards for LANs. Other countries have similar groups; for example, the British counterpart of IEEE is the Institution of Electrical Engineers (IEE).
Internet Engineering Task Force The Internet Engineering Task Force (IETF) sets the stan- dards that govern how much of the Internet will operate (see www.ietf.org). The IETF is unique in that it doesn’t really have official memberships. Quite literally anyone is welcome to join its mail- ing lists, attend its meetings, and comment on developing standards. The role of the IETF and other Internet organizations is discussed in more detail in Chapter 8; also, see the box entitled “How Network Protocols Become Standards.”
1.4.3 Common Standards There are many different standards used in networking today. Each standard usually covers one layer in a network. Some of the most commonly used standards are shown in Figure 1-6. At this point, these models are probably just a maze of strange names and acronyms to you, but by the end of the book, you will have a good understanding of each of these. Figure 1- provides a brief road map for some of the important communication technologies we discuss in this book. For now, there is one important message you should understand from Figure 1-6: For a network to operate, many different standards must be used simultaneously. The sender of a message must use one standard at the application layer, another one at the transport layer, another one at the network layer, another one at the data link layer, and another one at the physical layer. Each layer and each standard is different, but all must work together to send and receive messages. Either the sender and receiver of a message must use the same standards or, more likely, there are devices between the two that translate from one standard into another. Because different net- works often use software and hardware designed for different standards, there is often a lot of translation between different standards.
Future Trends 19
FIGURE 1-
A security robot on the IOT
Photo courtesy of the authors
driving test but also has fewer collisions than cars driven by humans. Other car developers are also developing autonomous vehicles. IoT technologies are not restricted to consumer use. To the contrary, they are used in many places such as manufacturing, process automation, decision analytics, and smart electrical grids. However, the underlying principle of all the applications is that IoT devices are connected to the Internet either through wired or wireless Ethernet. Figure 1-7 shows an IOT device that we encountered in a mall in Boston. It is semi-autonomous security robot, meaning it can be con- trolled by a human or set to roam its environment. Ten years ago, network managers would never have thought about the need to manage robots over their networks.
1.5.3 Massively Online You have probably heard of massively multiplayer online games, such as World of Warcraft, where you can play with thousands of players in real time. Well, today not only games are massively online. Education is massively online. Edx, Khan Academy, Lynda.com, or Code Academy have websites that offer thousands of education modules for children and adults in myriad fields to help them learn. Your class very likely also has an online component. You may even use this textbook online and decide whether your comments are for you only, for your instructor, or for the entire class to read. In addition, you may have heard about massive open online courses, or MOOC. MOOC enable students who otherwise wouldn’t have access to elite universities to get access to top knowledge without having to pay the tuition. These classes are offered by universities, such as Stanford, UC Berkeley, MIT, UCLA, Carnegie Mellon, and of course, Indiana University, free of charge and for no credit (although at some universities, you can pay and get credit toward your degree).
20 Chapter 1 Introduction to Data Communications
Politics has also moved massively online. President Obama reached out to the crowds and ordinary voters not only through his Facebook page but also through Reddit and Google Hangouts. President Trump’s use of Twitter is unprecedented. He can directly reach millions of followers—a strategy that paid off in the 2016 elections. Finally, massively online allows activists to reach masses of people in a very short period of time to initiate change. Examples of use of YouTube videos or Facebook for activism include the Arab Spring, Kony 2012, or the use of sarin gas in Syria. So what started as a game with thousands of people being online at the same time is being rein- vented for good use in education, politics, and activism. Only the future will show what humanity can do with what massively online has to offer. What these three trends have in common is that there will be an increasing demand for pro- fessionals who understand development of data communications and networking infrastructure to support this growth. There will be more and more need to build faster and more secure net- works that will allow individuals and organizations to connect to resources, probably stored on cloud infrastructure (either private or public). This need will call not only for engineers who deeply understand the technical aspects of networks but also for highly social individuals who embrace technology in creative ways to allow business to achieve a competitive edge through utilizing this technology. So the call is for you who are reading this book—you are in the right place at the right time!
1.6 IMPLICATIONS FOR CYBER SECURITY
At the end of each chapter, we provide key implications for cyber security that arise from the topics discussed in the chapter. We draw implications that focus on improving the management of networks and information systems as well as implications for cyber security of an individual and an organization. There are three key implications for management from this chapter. First, networks and the Internet change almost everything. Computer networks and the Internet are designed to quickly and easily move information from distant locations and to enable individuals inside and outside the firm to access information and products from around the world. However, this ease of doing work on the Internet makes it also easy for cyber criminals to steal files from your computer or to put files on your computer (such as viruses or malware). Understanding how computer networks and the Internet work and how computers communicate via networks is the first step toward defending your own computer and the computers on a company’s network. Second, today’s networking environment requires that a wide variety of devices could con- nect. Employees’ use of their own devices under BYOD policies increases security risks, as does the move to the IoT. Several security experts say that IoT doesn’t stand for Internet of Things; it stands for Internet of Targets. Individuals and companies have to balance BYOD and IoT risks and rewards to create a useful and secure computing infrastructure. Third, as the demand for network services and network capacity increases, so too will the need for secure storage and server space and secure transfer of data. Finding efficient ways to securely store all the information we generate will open new market opportunities. Today, Google has almost a million Web servers (see Figure 1-8). If we assume that each server costs an average of $1,000, the money large companies spend on storage is close to $1 billion. Capital expenditure of this scale is then increased by money spent on power and staffing. One way companies can reduce this amount of money is to store their data using cloud computing. The good news is that more and more cloud providers meet or exceed government required security measures for data storage and transfer.
