Connecting with Computer Science, 2e Chapter 5 The InternetConnecting with Computer Science, 2e 2 Objectives • In this chapter you will: – Learn what the Internet really is – Become familiar with the architecture of the Internet – Become familiar with Internet-related protocols – Understand how TCP/IP protocols relate to the Internet – Learn how IP addresses identify devices connected to the InternetConnecting with Computer Science, 2e 3 Objectives (cont’d.) • In this chapter you will (cont’d.): – Learn how DHCP can be used to assign IP addresses – Learn how routers are used throughout the Internet – Learn how a DNS server translates a URL into an IP address – Learn how port numbers are used with IP addresses to expand Internet capabilities – Learn how NAT is used in networkingConnecting with Computer Science, 2e 4 Objectives (cont’d.) • In this chapter you will (cont’d.): – Learn how to determine your own TCP/IP configuration – Learn how HTML and XML are used with the World Wide Web – Learn how to develop a simple Web page by using HTML – Learn how search engines make the World Wide Web more usableConnecting with Computer Science, 2e 5 Why You Need to Know About…The Internet • Internet: – Revolutionary information technology – Impacts everything • Business • Education • Knowledge and learning • Field of computing: – Heavily involved in all aspects of the Internet revolutionWhat Is the Internet? • Collection of LANs and WANs – Connected to form a giant WAN • Internet service provider (ISP) – Provides access to the Internet and other related services • No single Internet owner – Some groups propose rules – Other groups provide management – Personal involvement in the Internet often benefits many others Connecting with Computer Science, 2e 6The Architecture of the Internet • Internet connections – Communication lines leased from phone company to an ISP • Desktop linked via communication wire, wireless access point, cable TV system – Point of presence (POP) • An access point to the Internet • Connected to larger ISP with larger POP – National backbone provider (NBP) • Provides high-speed network communication lines for use by ISPs Connecting with Computer Science, 2e 7Connecting with Computer Science, 2e 8 Figure 5-1, Internet data can pass through several levels of ISPs The Architecture of the Internet (cont’d.)Connecting with Computer Science, 2e 9 Protocols • Set of rules facilitating communication • Many protocols are involved with the Internet – Hypertext Transfer Protocol (HTTP) – Simple Mail Transfer Protocol (SMTP) – File Transfer Protocol (FTP)Connecting with Computer Science, 2e 10 TCP and IP • TCP (Transmission Control Protocol) – Responsible for reliable delivery of data – Separates data into manageable, fixed-size packets – Establishes virtual circuit for transmission – Manages packet sequencing – Retransmits packets received in error – Header appended to data segment contains relevant informationConnecting with Computer Science, 2e 11 Table 5-1, TCP header fields TCP and IP (cont’d.)Connecting with Computer Science, 2e 12 Table 5-2, IPv4 header fields TCP and IP (cont’d.)Connecting with Computer Science, 2e 13 IP Addresses • Central to the operation of Internet Protocol – Provide a unique identifying device number – Most widespread version (IPv4): 32-bit value • Represented as a set of four decimal numbers separated by periods – New version of IP (IPv6): 128-bit addresses • Each IP address decimal number represents 8 bits • Pool of IPv4 addresses are separated into groups – Classes designated by A, B, C, D, and E • Several reserved addressesConnecting with Computer Science, 2e 14 Figure 5-2, IP address classes IP Addresses (cont’d.)Connecting with Computer Science, 2e 15 IP Addresses (cont’d.) • ISPs – Allocate IP addresses to other ISPs and home users • Internet Assigned Numbers Authority (IANA) – Maintains global high-level registry of IP addresses • American Registry for Internet Numbers (ARIN) – Allocates IP addresses to NBPs and ISPs • IP supports subnetting – Block of IP addresses forming a separate network from a routing standpointConnecting with Computer Science, 2e 16 DHCP • Dynamic Host Configuration Protocol (DHCP) – Used between a computer and a router – Allows for automatic assignment of IP addresses – Computer uses DHCP to get IP address from router • Time saving for the network administrator – Sets up server to allocate block of addresses – After configuration: • Nodes moved around • New computers added without determining available IP addressesConnecting with Computer Science, 2e 17 Routers • Device or software in a computer – Determines the next network point to which a packet should be forwarded • IP packets routed to correct destination via a number of different routes • Packet sent on another line if original line damaged or busy • Specialized computer used to join networks • Make the Internet possible • Work in a manner similar to post officeConnecting with Computer Science, 2e 18 Figure 5-3, Routers provide many alternative routes for packets Routers (cont’d.)Routers (cont’d.) • Time to live (TTL) field in the IP header – Enables routers to discard packets traversing the network for too long • TCP – Ensures reliable delivery of data – Verifies data received in the packet – Uses sequence numbers to order packets • Combination of TCP and IP – Ensures data sent from one computer to another gets there in a fast, orderly, reliable manner • Basis for the Internet Connecting with Computer Science, 2e 19Connecting with Computer Science, 2e 20 High-Level Protocols • Protocol suite compares to OSI layers – TCP and IP span Session, Transport, Network layers – SMTP, HTTP, FTP, and Telnet are “above” TCP and IP in the networking model • High-level protocols use TCP/IP – TCP splits messages into packets, if necessary – TCP layer adds header and forwards to IP for address – IP sends packets to Data
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