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

2. 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

3. 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

4. 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

5. Figure 2-1

6. 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)

7. 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

8. 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)

9. 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

10. 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

11. Figure 2-2

12. 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

13. 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

14. 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

15. 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 )
Internet hosts may also have an optional host name (such as gsaix2.cc.gasou.edu)

16. 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

17. 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

18. Figure 2-4

19. 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

20. 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

21. Figure 2-5

22. 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)

23. Table 2-2

24. 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)

25. Figure 2-6a

26. Figure 2-6b

27. Table 2-3

28. 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

29. 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)

30. Figure 2-7

31. 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

32. 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”

33. 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

34. TCP/IP Operation Figure 2-8

35. 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 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

36. 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

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

38. 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

39. Figure 2-10

40. 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

41. 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

42. 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

43. Local ISP Configuration Figure 2-11

44. ISP with Multiple Internet Access Options

45. Regional ISP Configuration

46. Major U.S. MAEs and NAPs

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