What Is the Internet?A network of networks, joining many government, university and private computers together and providing an infrastructure for the use of E-mail, bulletin boards, file archives, hypertext documents, databases and other computational resourcesThe vast collection of computer networks which form and act as a single huge network for transport of data and messages across distances which can be anywhere from the same office to anywhere in the world.Written by William F. Slater, III1996President of the Chicago Chapter of the Internet SocietyCopyright 2002, William F. Slater, III, Chicago, IL, USA

The largest network of networks in the world.Uses TCP/IP protocols and packet switching .Runs on any communications substrate.What is the Internet?From Dr. Vinton Cerf, Co-Creator of TCP/IP

Brief History of the Internet1968 - DARPA (Defense Advanced Research Projects Agency) contracts with BBN (Bolt, Beranek & Newman) to create ARPAnet1970 - First five nodes: UCLAStanfordUC Santa BarbaraU of Utah, and BBN1974 - TCP specification by Vint Cerf1984 On January 1, the Internet with its 1000 hosts converts en masse to using TCP/IP for its messaging

Internet Growth Trends1977: 111 hosts on Internet1981: 213 hosts1983: 562 hosts1984: 1,000 hosts1986: 5,000 hosts1987: 10,000 hosts1989: 100,000 hosts1992: 1,000,000 hosts2001: 150 175 million hosts2002: over 200 million hostsBy 2010, about 80% of the planet will be on the Internet

No. of Participating HostsOct. 90 - Apr. 98

The Internet was not known as "The Internet" until January 1984, at which timethere were 1000 hosts that were all converted over to using TCP/IP.Chart by William F. Slater, IIISept. 1, 2002Dot-Com Bust BeginsCopyright 2002, William F. Slater, III, Chicago, IL, USA

Chart1

4

5

23

01/72

01/73

09/73

62

01/75

01/76

111

01/79

01/80

213

235

562

1024

1961

2308

5089

28174

33000

56000

80000

130000

159000

313000

376000

535000

617000

727000

890000

992000

1136000

1313000

1486000

1776000

2056000

2217000

3212000

3864000

4852000

6642000

9472000

12881000

16146000

19540000

29670000

36739000

43230000

69883000

101000000

150576000

204670950

Hosts

Time Period

No. of Hosts

Growth of Internet Hosts *Sept. 1969 - Sept. 2002

host-count-history_to_January_1

Number of Internet Hosts

September 1973 - September 2002

DateHostsSource

9/694

01/705

01/7123

01/72no data

01/73no data

09/73no data

01/7462

01/75no data

01/76no data

01/77111

01/79no data

01/80no data

08/81213host table

05/82235

08/83562

10/841,024

10/851,961

02/862,308

11/865,089

12/8728,174old domain survey

07/8833,000

10/8856,000

01/8980,000

07/89130,000

10/89159,000

10/90313,000

01/91376,000

07/91535,000

10/91617,000

01/92727,000

04/92890,000

07/92992,000

10/921,136,000

01/931,313,000

04/931,486,000

07/931,776,000

10/932,056,000

01/942,217,000

07/943,212,000

10/943,864,000adjusted countsOld Counts

01/954,852,0005,846,0004,852,000

07/956,642,0008,200,0006,642,000

01/969,472,00014,352,0009,472,000

07/9612,881,00016,729,00012,881,000

01/9716,146,00021,819,00016,146,000

07/9719,540,00026,053,00019,540,000

01/9829,670,000new domain survey

07/9836,739,000

01/9943,230,000

01/0069,883,000

01/01101,000,000

01/02150,576,000

08/02204,670,950

host-count-history_to_January_1

Hosts

Time Period

No. of Hosts

Growth of Internet Hosts *Sept. 1969 - Sept. 2002

September 1, 2002

* The Internet was not known as "The Internet" until January 1984, at which time there were 1000 hosts that were all converted over to using TCP/IP.

Domain Name RegistrationJan. 89 - Jul. 97April 2001: 31,000,000 Domain Names!!!

TCP/IP AddressesEvery host on the Internet must have a unique IP addressThe IP address is a 32-bit number which we write in dotted decimal notationThe first part of the IP address is the network address the remainder is the host IDA subnet mask is used to determine the network address from a IP host addressAll hosts on the same network are configured with the same subnet mask

Network Address ExampleHost address: 192.252.12.14Subnet mask: 255.255.255.011000000.11111100.00001100.0000111011111111.11111111.11111111.00000000

11000000.11111100.00001100.00000000

To obtain the network address, AND the host IP with its subnet mask:Host IP:Mask:

Net addr:

which is:192.152.12.0

Obtaining an Internet Network AddressIP network addresses must be unique, or the Internet will not be stableThe Internet Network Information Centre (InterNIC) was originally responsible for issuing Internet network addressesToday, the Internet Assigned Number Authority (IANA) issues network addresses to Information Service Providers (ISPs)ISPs split networks up into subnets and sell them on to their customers

Domain Name System (DNS)IP addresses are used to identify hosts on a TCP/IP networkExample: 134.220.1.9Numbers are not friendly people prefer namesDNS is a protocol used to map IP addresses to textual namesE.g. www.wlv.ac.uk maps to 134.220.1.9

DNS on the InternetDNS names have a hierarchical structureExample: www.wlv.ac.ukcomnet fr uk us Root Level ac co aston wlv staffs ftp www clun Top-level domainSecond-level domainServer name

Internet Email AddressesThe Local part is the name of a special file stored on the mail server called the users mailboxThe Domain name is resolved using DNSThe mail server is also known as a mail exchangerLocal partDomain name of mail server@mel.ralph@wlv.ac.uk

Hypertext Transfer Protocol (HTTP)HTTP is the protocol used to access resources on the World Wide WebA browser application is used to send a request to the WWW server for a resource, e.g. a web page, graphics file, audio file, etc.The server responds by sending the resource (a file) to the client and closing the connection

RequestBrowser appWWW serverThe Internet(TCP/IP)Web page

Uniform Resource Locator (URL)URL is the standard for specifying the whereabouts of a resource (such as a web page) on the InternetA URL has four parts:

The protocol used to retrieve the resourceThe host where the resource is heldThe port number of the server process on the hostThe name of the resource filehttp://www.wlv.ac.uk:80/index.htmlProtocolHostPort numberName of web page

URL DefaultsA server will normally be setup to use standard defaultsThis enables the URL to be simplifiedIn the case of a Web server for exampleDefault port will be 80Default name for home page will be index.htmlHence the previous URL can be shortened to

http://www.wlv.ac.uk/

File Transfer Protocol (FTP)Protocol for copying files between client and an FTP serverUses a TCP connection for reliable transfer of files with error-checkingMost browsers support FTP, or you can use a dedicated FTP client program, e.g WS_FTPTrivial File Transfer Protocol (TFTP) is a lightweight version for small memory devicesftp://ftp.demon.co.uk/pub/

TelnetTelnet allows a user to run commands and programs remotely on another computer across the InternetThe user runs a Telnet client program on the local hostA Telnet server process must be running on the remote hostThe user must have the necessary permissions and password to access the remote host

Some Port Assignments21FTP23 Telnet25 smtp (mail)70 gopher79 finger80 HTTP

*5