Author: Shintaro Uno, Professor, Department of News Media, Faculty of Engineering, Aichi University of Technology
In this series, we will explain the basic knowledge of networks six times. This time we will introduce familiar networks like the Internet. When I think of a network, I think of the Internet, which connects PCs and smartphones. We may view web pages and exchange emails over the Internet. The Internet is built on a client-server model. In addition, PCs and smartphones are connected to the Internet through access networks such as fiber optics and wireless.
The first: What is town planning?
1. What is the Internet?
The Internet is a network that connects networks around the world. In other words, the Internet is a vast network made up of countless networks. By connecting PCs and smartphones to the Internet, we can connect not only to home networks but also to networks around the world. You can also use the Internet to browse websites, exchange e-mails and, more recently, on social networks and watch videos on YouTube.
The beginning of the Internet is said to date back to 1969. In 1969, the US Department of Defense started building a computer network called ARPANET (Advanced Research Projects Agency NETwork) across the United States. Four universities and research institutes (University of California, Los Angeles (UCLA), University of California, Santa Barbara) have dedicated data communication networks that use packet-switched technology that splits data into packets and sends it to the instead of circuit switching using the telephone network. The experiments were conducted in an interconnected fashion at the school (UCSB), the University of Utah, and SRI International. And we have achieved the transfer of mail and files between two or more computers.
In 1990, ARPANET was taken over by the National Science Foundation (NSFNET). At that time, the prototype of TCP/IP currently used on the Internet was applied as the communication procedure.
Figure 1 shows the basic configuration of today’s Internet. It splits the data from terminal A to terminal B and sends an IP packet in packet format. IP packets are first sent to the router via LAN (Local Area Network). After that, it will be sent to the input of the other network via some networks, and will be sent to terminal B via LAN. A router is a device that connects a network and determines which way the received packet is sent.
Figure 1: Basic Internet Configuration (cited by Shintaro Uno, Basics of Information and Communication Network, Morikita Publishing, 2016, P.5)
Originally, in computer-to-computer communication, the OSI (Open Systems Interconnection) reference model which realizes data communication between different models established by the International Organization for Standardization (ISO) in 1984 is common, as is its protocol (communication standard). But online…
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2. Internet connection
To connect to the Internet, you must use the line provided by the line operator and the Internet Service Provider (ISP) that connects to the Internet. However, the line operator and the ISP can be the same. In addition, there are cases where the line is used directly from the terminal such as in a general household, and there are cases where the line is connected from the terminal via LAN in an enterprise as shown in Fig. 1.
Initially, the Internet access method was a modem connection using the telephone network. After that, as a broadband connection that can be connected at any time via an ISDN connection, it will evolve into an ADSL connection, which is a dedicated line connection using a telephone line, a CATV connection, which is a satellite television network cable, and a broadband connection FTTH connection by fiber optic. In addition, wireless connections are multiplying, represented by smartphones. Table 1 summarizes the types of Internet connection lines.
Table 1: Internet Connection Line Types
|Fixed line||It is usually called an analog telephone line. You will need a modem to connect to the Internet. At first this method was used, but now it is rarely used.||Dial-up connection (narrowband connection)|
|ISDN (Integrated Services Digital Network)||Digital line also called full digital communication network. It was used from the 1990s to the 2000s, but is not widely used now due to its slow transmission speed (64Kbps to 1.5Mbps). A terminal adapter (TA) is required to connect a PC.||Dial-up connection (narrowband connection)|
|ADSL (asymmetric digital subscriber line)||You can use a landline phone, which is an analog line, to carry digital information and connect to the Internet. You will need an ADSL modem. It was popular until recently, but is being replaced by faster FTTH.||Broadband connection|
|CATV (Common Antenna Television、Community Antenna Television)||CATV is called cable television and was originally used to send television signals using a cable, but it can also be used for an Internet connection. You will need a cable modem to connect to the internet. The transmission speed is currently around 320 Mbps||Broadband connection|
|FTTH (fiber to the home)||A method of communication that uses fiber optics as a transmission line to ordinary households. Transmission speeds currently support up to 10 Gbps. An optical network unit (ONU) that converts optical and electrical signals is required.||Broadband connection|
|wireless||Connect to the Internet wirelessly from your smartphone, mobile phone or PC. Currently, it is connected by methods like LTE, WiFi, and WiMAX. 5G will start from 2020 and the transmission speed can reach 20 Gbps.||Broadband connection|
|leased line||Connect with a dedicated transmission line for businesses, universities, and research institutes, not for general households. There are analog and digital, and in the case of digital, different speeds are available from 0.5Mbps to 100Gbps.||Broadband connection|
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3. Client-server model
How does the service provided over the Internet work? Web services and mail services that are typical of Internet services are based on the client-server model. A client-server is a network in which two functions, a client and a server, are connected. A client is a computer that requests and receives a service. A server, on the other hand, is a computer that provides services. Figure 2 shows an example of a client-server system.
Figure 2: An example client-server model
When a client sends a request to a file server to store or retrieve a file, the server performs storage or retrieval of a specific file. Also, on the client…
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