Copyright Goodheart-Willcox Co., Inc. 512 Unit 3 Living Online example of a privately switched network is the ATM network, which requires a high degree of security. Internet Service Provider In order to connect to the Internet, an ISP must be used. An Internet service provider (ISP) is a company or organization that provides access to the Internet. The Internet is a network of networks, and each ISP owns one of those networks. Examples of ISPs are Verizon, Comcast, AOL, and many others. There is usually a fee charged by ISPs to access the Internet. The device used to connect to the ISP is called a modem. These connections are either hardwired or wireless. A wireless connection may be cellular based or Wi-Fi. Wi-Fi is the name given to wireless networks, and the ISP owns the Wi-Fi network. Wi-Fi connections may be fee-based or offered free of charge in many public locations, such as airports, hotels, and libraries. The task of a modem is to deliver the data channel for Internet transmissions. Its original use was via telephone landlines. Digital signals were modulated into analog transmissions, sent along telephone lines, and then demodulated back into digital signals for the computer. Hence the term modem, from modulate and demodulate. Modems come in a variety of configurations. At home or in businesses, ISPs provide modems that are wired to cable service, digital subscriber lines, or satellite dish service. Traditional landline modems are still in use, especially in remote areas where cable or satellite transmissions are not available. Cellular modems are used in mobile devices. In this case, the cellular carrier is the ISP. Internet Protocol A protocol is a system of agreed-on rules. Each network on the Internet has a unique Internet protocol address. The Internet protocol (IP) address is the number the networks on the Internet use to identify a particular network location. The host of the network is identifi ed by this number. Each device on a network has a subnet address relative to the host. This allows each computer connected to the Internet to be uniquely identifi ed. For example, the IP address 4.31.38.9 is for the Google home page. There are two schemes for assigning an address to a network: IPv4 and IPv6. In the IPv4 scheme, four bytes of data are assigned to the address. Each byte can hold 256 numbers, from 0 to 255. That provides 4,294,967,296 unique addresses (256 × 256 × 256 × 256). When the TCP/IP transmission scheme was invented, four billion addresses seemed like plenty. However, it is not enough for today’s technology needs when there are so many embedded devices that require connection to the Internet. The IPv6 scheme was developed to increase the number of possible IP addresses. In the IPv6 scheme, 16 bytes are assigned to each IP address. This provides 2128 or more than 8 × 1028 addresses. Each IPv6 address Computing Fundamentals 2.11.1 Computing Fundamentals 3.11 Living Online 1.1.1.2, 1.1.1.3 Living Online 2.2.3, 2.3.3 FYI FYI The IP address of a web page or other Internet resource may be changed at some point, so the IP address you have or fi nd may not be current. GS5 GS5 GS4