付録・索引

In computer science, a network is a system of computers and other technology that are interconnected to store and share information. Networks enable data communications, allowing users to interact on computers and other technology, such as cell phones. This gives users the ability to chat and exchange information on applications such as social media, emails, and video chats. For additional information on any of these topics, we suggest visiting Computer Networks: A Systems Approach by Larry Peterson and Bruce Davie, using the links included here.

Networks are comprised of various components. Applications are computer programs and software that enable us to use a network (https://book.systemsapproach.org/foundation/applications.html). Examples of applications include the World Wide Web, instant messaging, streaming services for movies and music, file-sharing, social media, and emails.

To build a robust network, computer scientists must consider the network’s requirements (https://book.systemsapproach.org/foundation/requirements.html). The requirements include the stakeholders who develop the network, as well as those who manage and operate the network. Scalable connectivity is a critical requirement to understand the needs that the network must currently meet, as well as the needs that must be met by the network as the organization grows and changes. Other requirements include the cost-effectiveness of the network, the support that the network provides for common services, such as an organization’s email application, and the network’s ability to be managed.

Like blueprints to construct buildings, computer networks need architecture to ensure the component parts are arranged and structured appropriately to ensure the network functions as needed (https://book.systemsapproach.org/foundation/architecture.html).

Computer networks cannot function without software, which refers to the programs that instruct computers on the tasks to perform. The different types of software include system, utility, and application. Examples of software include word processing and spreadsheet programs like Microsoft Word and Excel (https://book.systemsapproach.org/foundation/software.html).

Communication links are vital to connect the various nodes and users in a network. This requires tools like copper wire, optical fiber, and the air for wireless links (https://book.systemsapproach.org/direct/ perspective.html). Then processes like encoding (https://book.systemsapproach.org/direct/encoding.html), framing (https://book.systemsapproach.org/direct/framing.html), and error detection (https://book.systemsapproach.org/direct/error.html) are necessary to develop a reliable transmission (https://book.systemsapproach.org/direct/reliable.html). Also, it’s important to recognize that different types of communication links are needed for different types of networks, such as multi-access (https://book.systemsapproach.org/direct/ethernet.html), wireless (https://book.systemsapproach.org/direct/ wireless.html), and access (https://book.systemsapproach.org/direct/access.html).

To understand the concept of a computer network, consider the Internet, which is a global network that connects millions of people, enabling them to communicate and share information (https://book.systemsapproach.org/scaling/global.html).

The Internet is a good example of a network of networks, since it actually is comprised of many smaller networks that are interconnected (https://book.systemsapproach.org/internetworking/basic-ip.html).

To ensure that the Internet and other computer networks can function, they must have protocols, which are standardized rules to guide how data is formatted and processed. Protocols enable networks to transmit information (https://book.systemsapproach.org/e2e/problem.html). Common protocols include simple demultiplexor (https://book.systemsapproach.org/e2e/udp.html), reliable byte stream (https://book.systemsapproach.org/e2e/tcp.html), remote procedure call (https://book.systemsapproach.org/ e2e/rpc.html), and transport for real-time (https://book.systemsapproach.org/e2e/rtp.html). Web services also have protocols, including standards issued by the World Wide Web Consortium (https://book.systemsapproach.org/applications/traditional.html#web-services).

To use a network, such as the Internet, users rely on end systems, such as personal computers, tablets, and cell phones. End systems also include components like servers for email and even game consoles that are connected to the Internet. End system devices operate at the edge of the Internet, which is the point where such devices are connected to the network (https://book.systemsapproach.org/direct/trend.html).

To enable communication, networks rely on the client, which sends a request to gain access to a network’s file, and the server, which makes a file available by providing access (https://book.systemsapproach.org/ foundation/requirements.html#support-for-common-services).

Access networks are an example of the client-server relationship in networks (https://book.systemsapproach.org/direct/access.html). Internet service providers and cable service are examples of access networks, which enable users to connect to a network via personal devices like computers, cell phones, and TVs.

While networks often rely on wired links to function, many networks are wireless. Popular wireless technologies include Bluetooth, Wi-Fi, and 4G cellular (https://book.systemsapproach.org/direct/wireless.html).