Chapter 2 Introduction to the Internet Part 1: Data Communications in the Information Age

Learning Objectives Be able to distinguish between an internet, the Internet, and an intranet Be able to trace the history of the Internet Identify and briefly describe important Internet technologies Describe the distinctions between the Internet and the World Wide Web Identify and briefly describe key TCP/IP protocols Identify and briefly describe the major text-based Internet services Describe the different ways of gaining access to the internet Discuss the roles of ISP’s in Internet Access

What is the Internet? An internet is an interconnection of two or more networks that makes them appear to be one continuous network A company may have an internet (or enterprise network) that is not connected to the Internet The Internet is a “network of networks” linking commercial, academic, and government computers in all but a handful of countries worldwide It is a public network: individuals are able to gain access to the Internet and use its resources in a variety of ways An intranet is a private network that uses Internet technology such as hypertext documents and Internet protocols to store and retrieve data

Internet Browsers and Hypertext Most Internet users utilize browsers such as Internet Explorer or Netscape Navigator to access Web pages and access hypertext links Browsers enable microcomputer, PDA, and Internet-ready cell phone users to “surf” the Internet Clickable hypertext links enable Internet users to move effortlessly among Web pages. Hypertext is essentially text in a document or Web page that contains links to other documents or text Much of the text found on a browser screen is hypertext, as illustrated in Figure 2-1

Figure 2-1

Internet History The Internet began as a concept in 1964 when researchers at the Rand Corporation introduced the concept of packet-switching networks Packet-switching networks (PSNs) break messages into smaller packets for transmission over the network and use switches to get messages to their destinations The physical implementation of the Internet began in 1969 as a 4-node packet-switching network called ARPAnet. ARPAnet was named for and sponsored by the U.S. Defense Department’s Advanced Projects Research Agency (ARPA)

Internet History (Continued) By 1984, over 1,000 computers were connected to ARPAnet Until 1983, MILNET was part of the Internet; it connected nodes in military organizations, research organizations, and colleges and universities involved in military-sponsored research ARPAnet was officially shut down in 1984, but its remaining nodes and subnets continued to function

Internet History (Continued) During the 1980s, several regional networks such as BITNET and CSNET joined the Internet In 1986, the National Science Foundation (NSF) connected its five supercomputer networks, called NSFnet, to the Internet. After this happened, the resulting network of networks became known as the Internet In 1987, the NSF assumed responsibility for managing the backbone network and created the NSF Network Service Center (NNSC)

Internet History (Continued) By 1989, over 80,000 hosts were interconnected via the Internet backbone In 1991, NFSnet lifted its restrictions on using the Internet for commercial purposes In 1992, the first Internet-based e-commerce applications emerged In 1993, NSF replaced the NNSC with InterNIC (Internet Network Information Center) NSFnet served as the major backbone network on the Internet until 1995 when the NSF quit all direct support of the Internet in order to return to its original status as a research network By 1997, there were approximately 16 million Internet hosts representing all but a few countries worldwide By 2001, the number of Internet hosts surpassed 100 million

The Internet Today Today’s Internet is best described as a high-speed backbone network (see Figure 2-2) to which networks in businesses, education institutions, and government agencies worldwide are attached The Internet remains a public, cooperative, and independent network No single person, government, institution, or company owns the Internet

Figure 2-2

Internet Governance Several organizations play a key role in the ongoing evolution of the Internet through the development of recommendations and standards and by addressing other issues The major responsibilities of several of the major organizations involved in Internet governance are summarized in Table 2-1

Key Internet Advisory Groups and Governance Organizations Abbreviation Full Name W3C World Wide Web Consortium IAB Internet Architecture Board ICANN Internet Corporation for Assigned Names and Numbers IESG Internet Engineering Steering Group IETF Internet Engineering Task Force ISOC Internet Society

Internet Fundamentals Each network attached to the Internet must contain at least one host A network attached to the Internet may be subdivided into smaller segments called subnets Routers are used to send packets across the Internet from one network to another There may be multiple hops within the Internet backbone as messages make their way from one network to another An organization may use internal routers to interconnect subnets. These fundamentals are illustrated in Figure 2-3

Internet Hosts and Nodes In the early days of the Internet, only large computers (mainframes or midrange computers) had the power needed to attach to the Internet. Because these locally provided the application processing services for multiple terminal users, they were called “hosts” Today it has become common to use host to refer to the Internet’s large computers and servers that function as major repositories of files or applications, and nodes to refer to the microcomputers, terminals, and other computers in a network To use the Internet, every host and node must have an IP address (such as 128.191.17.15) Internet hosts may also have an optional host name (such as gsaix2.cc.gasou.edu)

Subnets A subnet is a portion of a network A large network is often subdivided into multiple interconnected, but independent, segments or domains in order to improve network performance or security All the computers that make up a single LAN are typically included in the same subnet Each IP address is made up of two major parts: network address and node address. When subnets are created, part of the node address is used to designate the subnet that the node is in

Routers Routers are data communication devices that are capable of forwarding packets from a computer on one network to computers attached to any other interconnected network Routers make the Internet transparent to users; they make it look like a single network rather than the like the set of interconnected networks that it really is Routers read the packets they receive and use the IP address of the destination host or node to determine how to forward the packet The path that a packet takes across the routers in the Internet (or an internet) is called its route Most consumers and businesses gain access to the Internet via the routers at ISPs (Internet service providers). This is illustrated in Figure 2-4

Figure 2-4

The World Wide Web The World Wide Web is arguably the best known and most widely used Internet service According to the Internet User’s Guide, the Web can be defined as “a hypertext-based, distributed information system created by researchers at CERN in Switzerland” Tim Berners-Lee is credited with developing the concept of a worldwide collection of electronic documents that include hyperlinks to other related documents to enable users to move quickly from one document to another regardless of whether they are stored on the same host or on hosts in different networks By 2000, the Web was estimated to include at least 2 billion unique Web pages and to be growing at the rate of more than 7 million pages each day

WWW Fundamentals An electronic document on the Web is called a Web page A collection of related Web pages that can be accessed from the same starting location is called a Web site Most Web sites have a starting point, and central reference point, called a homepage Each Web page at each Web site has a unique address or URL (uniform resource locator). A URL specifies the protocol, domain name, and path for the Web page (see Figure 2-5) HTTP (Hypertext transport protocol) translates a URL into the IP address of the host on which a requested Web page is stored. Once the host is contacted, HTTP uses the path to access the requested page and transfer it to the user’s computer

Figure 2-5

Web Servers The Web pages that comprise a Web site are stored on one or more servers called Web servers. Each Web server must have: An IP address to uniquely identify it Hardware capable of being connected to the Internet and handling visitor requests A link to the Internet with sufficient bandwidth to ensure acceptable performance and responsiveness to Internet user requests for Web pages Web server software (see Table 2-2)

Table 2-2

Browsers Internet users are able to access and view Web pages by using browsers such as Netscape Navigator and Internet Explorer The layout of the browser display is controlled by the Hypertext Markup Language (HTML) standard that it supports HTML uses tags to define the content and formatting of a Web page (see Figures 2-6a and 2-6b) Browser plug-ins and helper applications may be needed to display Web page multimedia content (see Table 2-3)

Figure 2-6a

Figure 2-6b

Table 2-3

Firewalls A firewall is software (or a hardware/software combination) that sits between the Internet and an enterprise network in order to monitor and control the traffic between them Firewalls are often used to protect and maintain the privacy of intranets Firewalls help to protect networks from hackers and virus infections

Firewall Categories There are several types of firewalls including: packet filter firewalls application firewalls proxy firewalls Border routers often include firewall software, however, firewalls can also be implemented in hosts (see Figure 2-7)

Figure 2-7

TCP/IP: The Internet Protocol The TCP/IP protocol suite consists of five relatively independent layers: Application Transport (host-to-host) Internet Network access Physical

Internet Protocol (IP) The Internet Protocol (IP) is found at the Internet layer of the TCP/IP protocol suite It is responsible for routing data packets across multiple interconnected networks (such as the Internet) To work, it must be implemented in all hosts, nodes, and routers, hence, each must have an “IP address”

Transmission Control Protocol (TCP) TCP is the key communication protocol found at the transport or host-to-host layer of the TCP/IP protocol suite It is responsible for ensuring that data is exchanged reliability between hosts located in different networks This involves ensuring that all of a sender’s data packets are delivered to the receiver in same order in which they were sent TCP only needs to be implemented in hosts

TCP/IP Operation Figure 2-8

Other Important TCP/IP Protocols Important Application layer TCP/IP protocols include: Hypertext Transport Protocol (HTTP) - transferring Web pages File Transfer Protocol (FTP) - downloading/uploading files Simple Mail Transfer Protocol (SMTP) - transferring e-mail among TCP/IP hosts Simple Network Management Protocol (SNMP) - collecting and reporting data traffic within a network Telnet (enables users to run applications on hosts in other networks) Wireless Application Protocol (WAP) - enables cell phones, PDAs, etc. to receive and display Web pages

IPv6: Internet Protocol Version 6 IPv4 is the current version of IP; because it only supports 32-bit addresses, we will run out of IP addresses IPv6 supports 128-bit addresses (see Table 2-5) and is being used on Internet2 Other key upgrades in IPv6 include: header changes to improve quality of service, security, and privacy interoperability with IPv4

Internet Services Major Internet services include: search engines text-based applications chatting and instant messaging applications

Search Engines Search engines enable users to find Internet resources by supplying keywords. Numerous search engines are widely used (see Table 2-6) Search engines have three major parts (see Figure 2-10): spider index search engine

Figure 2-10

Text-based Internet Applications Archie Gopher Veronica Jughead Wide Area Information Server (WAIS) Usenet Internet Relay Chat (IRC) Talk Instant messaging (IM) Two-way messaging and SMS

Internet Access Options Individuals can access the Internet in a variety of ways including: At work via networks with Internet access In educational institutions Through public services (e.g. public libraries) Via freenets ISP subscriptions Via wireless networks

Internet Service Providers ISPs may be local, regional, national, or international in scope Individuals should consider multiple factors when selecting an ISPs (see Table 2-9) ISP configurations often include multiple servers in addition to a router for Internet access and modem banks (see Figure 2-11) Some ISPs support multiple subscriber connection options (such as DSL and cable modem connections) in addition to dial-in access (see Figure 2-12). Some support wireless Internet access Local ISPs typically gain Internet access via regional ISPs, network access points (NAPs) or metropolitan area exchanges (MAEs)--see Figures 2-13 and 2-14

Local ISP Configuration Figure 2-11

ISP with Multiple Internet Access Options

Regional ISP Configuration

Major U.S. MAEs and NAPs

Chapter 2 Introduction to the Internet Part 1: Data Communications in the Information Age