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 resources• The 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 Society
What is the Internet?• The largest network of networks in the world.• Uses TCP/IP protocols and packet switching .• Runs on any communications substrate. From Dr. Vinton Cerf, Co-Creator of TCP/IP
ARPANET• In 1968, the Defense Department began developing ARPANET ARPA – Advanced Research Projects Agency • WAN (wide area network) designed to connect DoD researchers and university researchers • Development of WANS, routers and the Internet Protocols • used packet-switching
ARPANET– ARPANET went on line in 1969 connecting 4 computers in California and Utah • In 1972, Email was invented • In 1973, APRANET went international with sites in England and Norway • The ARPRANET grew rapidly in the 1980s: – By 1981: 213 computers – By 1984: 1000 computers – By 1987: 10000 computers
From APRANET to INTERNET• In 1982, the military portion of the ARPANET was separated into MILNET• Supervision of ARPANET was passed to the NSF (the National Science Foundation)• In 1983, the new TCP/IP protocol was added
From APRANET to INTERNET• By 1990, the original ARPANET backbone was decommissioned in favor of newer long-distance data transmission networks – The collection of NSF-sponsored backbones and the regional sites it connected together became the Internet
From Internet to WWW• By the early 1990s, the Internet was primarily used to connect Universities together – Other commercial WANs began to connect to the Internet • Genie, CompuServe, Prodigy, etc – Popular applications were Email, FTP
From Internet to WWW– In 1994, a graphical Internet browser was developed to allow easy access to materials stored on the Internet • the first web browser was called Mosaic– This gave birth to the World Wide Web, the collection of interlinked files on the Internet • which has led to full-scale exploitation of the Internet for global communications
Commercialization of the Internet• Before 1995 commercial traffic was forbidden on the taxpayer-funded NSF• In 1995 when NSF eliminated all Internet subsidies commercial Internet development took off.
The Internet TodayAreas of the world andThe number of computers Part of the Internet backbone
Who Controls the Internet?• No one• The Internet is made up of privately owned computers and networks, all of which agree to implement the Internet protocols.
Who Controls the Internet?• Some organizations control certain aspects of the Internet – W3C, World Wide Web Consortium issues standards related to all aspects of the Web.• The Internet is everywhere and yet it is not in any one location. – In fact, the Internet was designed to survive a nuclear war
Brief History of the Internet• 1968 - DARPA (Defense Advanced Research Projects Agency) contracts with BBN (Bolt, Beranek & Newman) to create ARPAnet• 1970 - First five nodes: – UCLA – Stanford – UC Santa Barbara – U of Utah, and• 1974 - TCP specification by Vint Cerf• 1984 – On January 1, the Internet with its 1000 hosts converts en masse to using TCP/IP for its messaging
A Brief Summary of the Evolution of the Internet Mosaic Age of eCommerce Begins WWW Created 1995 Internet Created 1993 Named 1989 and Goes TCP/IP TCP/IP Created 1984 ARPANET 1972 1969 Hypertext Invented Packet 1965 Switching First Vast Invented Computer 1964 Network Silicon Envisioned A Chip 1962 Mathematical 1958 Theory of Memex CommunicationConceived 1948 1945 1945 1995
From Simple, But Significant Ideas Bigger Ones Grow 1940s to 1969 We will prove that packet switching works over a WAN. Hypertext can be used to allow rapid access to text data Packet switching can be used to send digitized data though computer networks We can accomplish a lot by having a vast network of computers to use for accessing information and exchanging ideas We can do it cheaply by using Digital circuits etched in silicon. We do it reliably with “bits”, sending and receiving data We can access information using electronic computers1945 1969
From Simple, But Significant Ideas Bigger Ones Grow 1970s to 1995 Great efficiencies can be accomplished if we use The Internet and the World Wide Web to conduct business. The World Wide Web is easier to use if we have a browser thatTo browser web pages, running in a graphical user interface context. Computers connected via the Internet can be used more easily if hypertext links are enabled using HTML and URLs: it’s called World Wide Web The ARPANET needs to convert to a standard protocol and be renamed to The Internet We need a protocol for Efficient and Reliable transmission of Packets over a WAN: TCP/IP Ideas from 1940s to 19691970 1995
The Creation of the Internet• The creation of the Internet solved the following challenges: – Basically inventing digital networking as we know it – Survivability of an infrastructure to send / receive high-speed electronic messages – Reliability of computer messaging
IPAddressesIP – Internet Protocol• an IP address is a 32-bit number • NKU‟s web server has the IP 126.96.36.199• routers throughout the Internet relay messages from one location to another using the IP address of the intended recipient
Internet Addresses and Aliases• Its hard to remember these long numbers• We give our machines “aliases” instead – NKU‟s web server is known as sappho.nku.edu (or www.nku.edu)• We use aliases for convenience, it is necessary to convert from an alias to an IP address when sending a datagram – Domain Name Servers (DNS) are tables stored on various computers on the Internet that do this conversion for us
The World Wide Web• Many refer to the Internet today as the Web, or the world wide web (www) – In fact, the WWW is an application that runs on the Internet • It has a collection of files stored on certain computers on the Internet known as web servers – What makes it a web? • Links
The World Wide Web– In a Web page, there are links to other files • Links are commands that tell a computer to go out and retrieve another file over the Internet • But unlike older Internet technologies where the user had to know the IP address, the link contains the address so there is nothing to memorize • Click on a link your computer sends a message across the Internet requesting the specified document (web page) referenced in the link – the receiving computer sends the page back and your computer loads it and displays it in your browser
URLs• A link includes the location of the document being referenced – These links are called URLs • Uniform Resource Locators – URLs have four parts: • Protocol (http, ftp) : // – the protocol determines what will be done with the document when it is received, http: display in a browser, ftp: save to disk • Server - the web server storing the document you want • Path - the directory where the document is stored • Document (file) name – Example: http://www.nku.edu/~foxr/CSC150/ch1.ppt – NOTE: just because there is a link, doesn‟t mean it has the right address – the address may be old, the file may be gone, this leads to broken links (or dead links)
Web Browsers and Web Servers• Web servers – Computers that store web pages and allow client computers to access them• Web browsers – allow clients to access web server • If you have web pages on your computer but no web server, no one can see those pages (outside of you)• A web site is a collection of web documents available on a computer running the web server software – The home page (or index page) is the main page, the first one retrieved
Accessing a Web Page 3. Your request NATIONAL 4. Your request goes to a goes to a national network access backbone network. point (NAP).1. You request Ra Web page. E G I O N A L 5. Your request 2. Your request reaches the WebYOU ARE site’s server and the goes to yourHERE ISP’s point of Web page is sent presence (POP). back to you in packets.
Internet Computer in scramento Requests information fromCommunications: A computer in Savannah 1) Message packaged A Variety of 2) 3) Message sent by MODEM To Internet POP Technologies 4) To another component of the Internet backbone via microwave 5) To satellite 6) To receiving station in NY 7) By microwave to another station in Atlanta 8) By phone to Georgia State 9) Where the message is received by destination machine
Configuring Your Computer• What you need to get to the Internet: – TCP/IP (which is available in the OSs) – Communications equipment to connect your computer to a network:• A physical connection to the Internet – Dialup access : modem – DSL, Cable or Satellite access • Access the Internet through your signal provider using a special modem over the line to your house (coaxial, satellite dish or DSL line) – LAN access • such as from NKU – access via LAN is usually much better than through an ISP because of the use of T1 or better connections • Network card
Interoperability• The Internet is made up of many different – Types of computers (IBM PC, Mac, mainframes, Unix workstations, etc) – OSs (windows, Mac OS, Unix, Linux, VMX) – LANs (Ethernets, Appletalk networks, etc)• This makes the Internet a cross-platform network• All of these computers must be Interoperable – they must speak the “same language” – in this case, the language is the TCP/IP protocol • Transmission Control Protocol/Internet Protocol – IP protocol dictates how addresses and routers work – TCP: reliable delivery, congestion control, service requested
Internet: Packet Switching NetworkMessages are dividedinto units calledpacketsEach packet is givena copy of thedestination addressand sent on its wayEach packet finds itsway independentlyacross the networkUpon receipt, thereceiving computerassembles thepackets in orderbefore displayingthe message to the user
Intranets• Because of the success of TCP/IP, many networks are being configured today to use TCP/IP – But rather than being a part of the Internet, they only connect local computers together – Thus, the organization has the same abilities as Internet users (email, ftp, messaging, etc) but communication remains local • A firewall might be placed between a company‟s Intranet and the Internet so that critical information can not be sent out and viruses and other harmful attacks can not make their way in • The firewall is special software running on a computer that acts as the point of contact (or connection) to the Internet – An Extranet is an Intranet that is open to certain pre- specified users, so in a way, its like opening up your network to only a portion of the Internet but where you dictate who gains access
Who Do You Trust?• The Web is a great source of information. One problem is that there are no rules about what people can say on their web sites – Inaccurate information – Irrelevant information – Out-of-date information• In examining information, keep in mind – who the author is – whose server it is – who the author‟s source is – keep in mind accuracy and currency (date) of data • the web is littered with web pages that haven‟t been updated in years!
The Future of the Internet• A billion Internet users by 2010? – Can the IP protocol support this? No • There are about 4 billion unique IP addresses available but there will not be enough to go around Class Network Machine Addresses Addresses There are not enough Class B addresses for all of the networks and many networks Class A 127 16 million that currently exist are outgrowing their Class B 16,000 65,000 Class C addresses Class C 2 million 254 • A newer version of IP addresses is being considered called IPv6 – 128 bit address
Future of the Internet – We will also have a problem supporting the need for super-fast connections to transfer large data files • such as music and movies• I2 (Internet 2) – a project for developing gigaPop – gigaPop: a gigiabit per second point of presence – access to a backbone service capable of transferring in excess of 1 Gbps.
Internet Growth Trends• 1977: 111 hosts on Internet• 1981: 213 hosts• 1983: 562 hosts• 1984: 1,000 hosts• 1986: 5,000 hosts• 1987: 10,000 hosts• 1989: 100,000 hosts• 1992: 1,000,000 hosts• 2001: 150 – 175 million hosts• 2002: over 200 million hosts• By 2010, about 80% of the planet will be on the Internet
No. of Participating Hosts Oct. „90 - Apr. „98
Having Internet Connectivity• To have complete Internet connectivity you must be able to reach all destinations on the net.• Your packets have to get delivered to every destination. This is easy (default routes).• Packets from everywhere else have to “find you”. This is done by having your ISP(s) advertise routes for you.
Internet service provider (ISP or IAP)ISP is a business or organization thatprovides consumers or businesses access tothe Internet and related services. In thepast, most ISPs were run by the phonecompanies. Now, ISPs can be started by justabout any individual or group with sufficientmoney and expertise. In addition to Internetaccess via various technologies such as dial-up and DSL, they may provide a combinationof services including Internet transit, domainname registration and hosting, web hosting.
ISP connection optionsTypical home user connection• Dial-up• DSL• Broadband wireless access• Cable modem• ISDN
ISP connection optionsTypical business connection• DSL• SHDSL• Ethernet technologies
DSL - Digital Subscriber LineDSL is one of the most prevalent formsof Internet connection. DSL provideshigh-speed networking over ordinaryphone lines using digital modems. DSLconnection sharing can be easilyachieved with either wired or wirelessbroadband routers.
Cable - Cable Modem InternetCable modem is a form of broadbandInternet connection. Cable Internetuses neighborhood cable televisionconduits rather than telephone lines,but the same broadband routers thatshare DSL Internet connections alsowork with cable.
Dial Up InternetDial up uses ordinary telephone linesbut, unlike DSL, dial up connectionstake over the wire, preventingsimultaneous voice calls. Dial uprouters are difficult to find, expensive,and generally do not perform wellgiven such a slow Internet pipe. Dial upis most commonly utilized in lightlypopulated areas where cable and DSLInternet services are unavailable
ISDN - Integrated Services Digital NetworkISDN works over telephone lines andlike DSL, supports simultaneous voiceand data traffic. Additionally, ISDNprovides 2 to 3 times the performanceof most dial up connections. Homenetworking with ISDN works similarly tonetworking with dial up.
Satellite InternetEnterprises like Starband, Direcwayand Wildblue offer satellite Internetservice. With an exterior-mountedmini-dish and a proprietary digitalmodem inside the home, Internetconnections can be established over asatellite link similar to satellitetelevision services.
POP(Point of presence)An Internet point of presence is an access pointto the Internet. It is a physical location thathouses servers, routers, ATM switches anddigital/analog call aggregators. It may be eitherpart of the facilities of a telecommunicationsprovider that the Internet service provider (ISP)rents or a location separate from thetelecommunications provider. ISPs typically havemultiple POPs, sometimes numbering in thethousands. POPs are also located in Internetexchange points and collocation centres.
Internet POP Design• Point of Presence (POP) – An access point to the Internet – A router is required to interface with the service provider – Demarcation point is where the ISP company ends and the private network of the customer begins.