In the previous two chapters, we briefly examined the general concept of an internet (lowercase i), contrasted it with the Internet, and introduced Internet-related terms such as intranet and extranet. We also presented a few TCP/IP-based application protocols such as the Simple Mail Transfer Protocol (SMTP) for e-mail, the File Transfer Protocol (FTP) for file transfers, and the Hypertext Transfer Protocol (HTTP) for Web applications. In this chapter, we expand our discussion of the Internet and its related protocols. We begin by defining the Internet from various perspectives. We then provide information about its history and contrast the Internet's early days to its current state. We also present other Internet-related initiatives and provide a brief discussion of its administration and governance structure. We next introduce the TCP/IP protocol suite. We trace its history and provide detailed information about several TCP/IP application-layer, transport-layer, and network-layer protocols. An outline of the major topics we discuss follows:

• Definition of the Internet (Question 1)

• Internet History (Questions 2 10)

• The Current Commodity Internet (Questions 11 12)

• Other Internet Initiatives: vBNS/vBNS+, Internet2, Next Generation Internet (Question 13)

• Internet Administration, Governance, and Standards (Questions 14 16)

• History of TCP/IP (Questions 17 22)

• TCP/IP Application Layer Protocols: SMTP, MIME, POP, IMAP, TELNET, FTP, HTTP (Questions 23 56)

• TCP/IP Transport Layer Protocols: UDP and TCP (Questions 57 71)

• TCP/IP Network Layer Protocol: IP (Questions 72 73)

• IPv4 Addresses and Subnetting (Questions 74 83)

• IP Address Assignments (Questions 84 85)

• IP Name Resolution (Questions 86 88)

• IPv6 (Questions 89 94)

• Internet Services, Resources, and Security (Questions 95 96)