Computer Networks

Summary

Computer networks consist of the hardware and software needed to support communications and the exchange of data between computing devices. The computing devices connected by computer networks include large servers, business workstations, home computers, and a wide array of smart mobile devices. The most popular computer network application is email, followed by exchanging audio and video files. Computer networks provide an infrastructure for the Internet, which provides support for the World Wide Web.

Definition and Basic Principles

A computer network is a collection of computer devices that are connected in order to facilitate the sharing of resources and information. Underlying the computer network is a communications network that establishes the basic connectivity of the computing devices. This communications network is often a wired system but can include radio and satellite paths as well. Devices used on the network include large computers, used to store files and execute applications; workstations, used to execute small applications and interact with the servers; home computers, connected to the network through an internet service provider (ISP); and mobile devices, connected to the network by radio wave transmissions. Middleware is the software that operates on top of the communications network to provide a software layer for developers to add high-level applications, such as a search engine, to the basic network.

The high-level applications are what most people using the network see as the network. Some of the most important computer network applications provide communications for users. Older examples of this are email, instant messaging, chat rooms, and videoconferencing. Modern examples of communications software are the multitude of social networks, such as Facebook and YouTube. Other high-level applications allow users to share files. One of the oldest and still quite popular file-sharing programs is the file transfer protocol (FTP) program. Another way to use computer networks is to share computing power. The Telnet program (terminal emulation program for TCP/IP networks) allowed one to use an application on a remote mainframe in the early days of networking, and modern Web services allow one to run an application on a mobile device while getting most of the functionality from a remote server.

Background and History

The scientists who developed the first computers in the 1950s recognized the advantage of connecting computing devices. Teletype machines were in common use at that time, and many of the early computers were “networked” with these teletype machines over wired networks. By 1960, American Telephone and Telegraph (AT&T) had developed the first modem to allow terminal access to mainframes, and in 1964, IBM and American Airlines introduced the SABRE (Semi-Automated Business Research Environment) networked airline reservation system.

The Defense Department created ARPANET (Advanced Research Projects Agency Network) in 1966 to connect its research laboratories with college researchers. The early experience of ARPANET led the government to recognize the importance of being able to connect different networks so they could interoperate. One of the first efforts to promote interoperability was the addition of packet switching to ARPANET in 1969. In 1974, Robert Kahn and Vinton Cerf published a paper on packet-switching networks that defined the TCP/IP protocol, and in 1980, the US government required all computers it purchased to support TCP/IP. When Microsoft added a TCP/IP stack to its Windows 95 operating system, TCP/IP became the standard wide-area network in the world.

The development of the microcomputer led to the need to connect these devices to themselves and the wide-area networks. In 1980, the Institute of Electrical and Electronics Engineers (IEEE) 802 standard was announced. It has provided most of the connectivity to networks since that time, although many wireless computing devices can connect with Bluetooth.

How It Works

Computer networks consist of the hardware needed for networking, such as computers and routers; the software that provides the basic connectivity, such as the operating system; and middleware and applications, the programs that allow users to use the network. In understanding how these components work together, it is useful to look at the basic connectivity of the wide-area network and contrast that to the way computers access the wide-area network.

Wide-area Networks. A wide-area network is one that generally covers a large geographic area and in which each pair of computers connects via a single line. The first wide-area networks consisted of a number of connected mainframes with attached terminals. By connecting the mainframes, a user on one system could access applications on every networked computer. IBM developed the Systems Network Architecture (SNA), which was a popular early wide-area network in the United States. The X.25 packet switching protocol standard provided a common architecture for the early wide-area networks in Europe. Later, as all computers provided support for the TCP/IP protocol, it became possible for different computer networks to work together as a single network. In the twenty-first century, any device on a single network, whether attached as a terminal by X.25 or as a part of a local area network (LAN), can access applications and files on any other network on the Internet. This complete connectivity allows browsers on any type of mobile device to access content over the World Wide Web because it runs transparently over the Internet.

Routing. A key to making the Internet operate efficiently is the large number of intermediate devices that route IP packets from the computer making a connection to the computer receiving the data. These devices are called routers, and they are the heart of the Internet. When a message is sent from a computer, it is decomposed into IP packets, each having the IP address of the receiver. Then, each packet is forwarded to a border router of the sender. From the border router, the packet is routed through a set of intermediate routers, using an algorithm-like best path, and delivered to the border router of the receiver and then the receiver. Once all the packets have arrived, the message is reassembled and used by the receiver.

Local Area Networks. A local area network (LAN) is a collection of computers, servers, printers, and the like that are logically connected over a shared media. A media access control protocol operates over the LAN to allow any two devices to communicate at the link level as if they were directly connected. There are a number of LAN architectures, but Ethernet is the most popular LAN protocol for connecting workplace computers on a LAN to other networks. Ethernet is also usually the final step in connecting home computers to other networks using regular, cable, and ADSL (Asymmetric Digital Subscriber Line) modems. The original coaxial cable Ethernet, developed by Robert Metcalfe in 1973, has been largely supplanted by the less expensive and easier to use twisted-pair networks. The IEEE 802.11 wireless LAN is a wireless protocol that is almost as popular as Ethernet.

Wireless Networks. A laptop computer's initial connection to a network is often through a wireless device. The most popular wireless network is the IEEE 802.11, which provides a reliable and secure connection to other networks by using an access point, a radio transmitter/receiver that usually includes border-routing capabilities. The Bluetooth network is another wireless network that is often used for peer-to-peer connection of cameras and cell phones to a computer and then through the computer to other networks. Cell phones also provide network connectivity of computing devices to other networks. They use a variety of techniques, but most of them include using a cell phone communications protocol, such as code division multiple access (CDMA) or Global System for Mobile Communications (GSM), and then a modem.

Applications and Products

Computer networks have many applications. Some improve the operation of networks, while others provide services to people who use the network. The World Wide Web supplies many exciting applications, and technologies such as teleconferencing and cloud computing have revolutionized computing, spurred on by the COVID-19 pandemic when the majority of workers and schoolchildren relied on these technologies from their homes.

Network Infrastructure. Computer networks are complex, and many applications have been developed to improve their operation and management. A typical example of the software developed to manage networks is Cisco's Internetwork Operating System (IOS) software, an operating system for routers that also provides full support for the routing functions. Another example of software developed for managing computer networks is the suite of software management programs provided by IBM's Tivoli division.

Communications and Social Networking. Communications programs are among the most popular computer applications in use. Early file-sharing applications, such as FTP, retain their popularity, and later protocols such as BitTorrent, which enables peer-to-peer sharing of very large files, and file hosting services like Dropbox, which provides cloud storage and online backup services, are used by all. Teleconferencing through platforms such as Zoom is used to create virtual workplaces, and Voice over Internet Protocol (VoIP) allows businesses and home users to use the Internet for digital telephone service with services provided by companies such as Vonage.

The earliest computer network communications application, email, is still the largest and most successful network application. One accesses email services through an email client. The client can be a stand-alone program, such as Microsoft Outlook or Windows Live Mail, or it can be web-based (webmail), accessed using a browser, such as Mozilla Firefox or Google Chrome. The email server can be a proprietary system such as IBM Notes or one of the many webmail programs, such as Gmail, Outlook, or Yahoo! Mail.

One of the most common types of applications for computer networks is social networking sites. Facebook was the most widely used online social network throughout the 2010s and early 2020s, although sites like X (formerly Twitter), TikTok, and YouTube were also very popular. Facebook was conceived by Mark Zuckerberg in 2004 while he was a student at Harvard University. Facebook members can set up a profile to share with other members. The site supports messaging, event scheduling, and news feeds. By setting up a "friend" relationship with other members, one can quickly rekindle old friendships and gain new acquaintances. Although Zuckerberg's initial goal was to create a friendly and interactive environment for students, Facebook became a way to promote businesses, organizations, and even politicians. Facebook does not charge a subscription fee and has a reasonably successful business model selling customer information, advertising, and working with partners. Facebook offers a separate communication platform called Messenger and an online store called Marketplace. Meta (formerly Facebook), the company that owns Facebook, also owns several other social media sites, including Instagram and WhatsApp, which boast over one billion monthly active users.

Cloud Computing.Cloud computing refers to the hosting of data and applications on remote servers and networks ("the cloud") instead of on local computers. Among other things, this makes the data and software services accessible from multiple locations, such as both home and office computers, as well as from mobile devices. This has benefits for data accessibility as well as businesses' approach to their technology needs, as cloud computing essentially allows them to outsource some of their information technology (both hardware and software) for an ongoing service fee rather than up-front capital costs. For individuals, it allows ready access to one's files and programs anywhere with internet access. Platforms include Microsoft Azure, Amazon Web Services, and Google Cloud Platform, among others. Communication services such as Slack and Microsoft Teams are further examples of cloud computing that gained popularity among businesses during the coronavirus pandemic.

Next to email, the most common application is word processing, and Microsoft Word is the dominant word processor. Microsoft offers online versions of Word and all its other Microsoft Office software through a service called Microsoft 365. Google offers similar cloud-based services, such as Google Docs and Google Drive. As more applications are produced to run in the cloud, it is predicted that this will become the dominant form of computing, replacing the desktop computers of the early twenty-first century.

Careers and Course Work

A major in computer science is the traditional way to prepare for a computer networking job. Students first need courses in ethics, mathematics, and physics to form the basis for a computer science degree. Then, they take about thirty-six hours of computer hardware and software courses. Those getting a computer science degree often take jobs developing network software or managing a network.

A major in information systems is another way to prepare for a computer networking job. Students must take courses in mathematics and business as a background for this degree. Then, they take about thirty hours of courses on information systems development. Those getting degrees in computer information systems often take jobs as network managers, especially in small businesses.

Networking and maintaining an internet presence are increasingly important to business development. Using social networking to advertise and stay connected to customers has opened social networking management jobs in nearly every industry. These individuals manage an individual or business's online presence across platforms.

In addition to the traditional academic programs that prepare someone for a computer networking job, many professional training programs result in certification. Novell was the first company to develop a certification program for its NetWare network operating system. Microsoft followed with its Microsoft Certified Professional program for the Windows Server operating system, which includes networking. The Cisco Certified Network Professional program is a large program that covers all networking, not just routers.

Social Context and Future Prospects

Developing computer networks and network applications has often resulted in legal issues. File exchange programs, such as Flickr, often gain quick popularity but can have copyright issues. Napster developed a successful peer-to-peer file exchange program but was forced to close in 2001 after only two years of operation by a court decision. Legislation has played an important role in developing computer networks in the United States. The initial deregulation of the communications system and the breakup of AT&T in 1982 reduced the cost of the base communications system for computer networks and thus greatly increased the number of networks in operation. Opening up NSFNET for commercial use in 1991 made the Internet possible.

In the 2020s, concerns about TikTok's privacy and data collection policies, among other issues, were at the forefront of legal issues in the tech industry. The US government's ban on the app led to a lawsuit, which overturned the ban in 2020. However, after further investigation, the government continued its plan to ban the app, citing national security concerns. Several TikTok users sued to keep the app available.

The emergence of cloud computing was also transformative, especially during the COVID-19 pandemic. Although security and privacy issues remain, people are increasingly using mobile devices to access a wide variety of internet services through the cloud. Using a smartphone, people can communicate with friends and associates, transact business, compose letters, pay bills, read books, and watch films.

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