Learning Resources
Lesson
The Basics
The internet is a network of inter-connected computers and computer networks. To understand the structure of the internet, a little history lesson is required
- 1957. In response to the USSR's Sputnik launch, the US create the ARPA (Advanced Research Projects Agency) to establish a US lead in science and technology
- 1962. The US government study issued a report calling for a packet switched network (a way of breaking information up into small 'packets' so they can be sent separately and reassembled when they get there - it is still in use) to ensure communications to control missiles in case of a nuclear attack
- 1968. ARPA awarded a contract to build ARPANET with 4 hosts (computers) connected at 50kps. The internet was born
- 1973. Development was begun on what was later called TCP/IP (transmission control protocol/internet protocol) as a means to interconnect different networks.
- 1974. Cerf and Kahn coin the term internet in a paper on TCP. By now there were 23 hosts
- 1976. Ethernet was invented using coaxial cable as a means of fast data transfer. Other networks were built and TCP/IP became the protocol for the internet. TCP/IP is the internet connection and data transfer protocol today. There were more than 111 hosts
- 1979. USENET was created as a decentralized news group network. All current news groups evolved from this project.
- 1981. Additional networks built. 213 hosts.
- 1983. The internet began to regulate itself with the creation of the Internet Activities Board. The Domain Name System (DNS) was created. DNS is the current method for locating computers on the internet.
- 1984. More networks. 1024 hosts
- 1985. Faster connections implemented (T1 lines at 1.544 Mbps). 1961 hosts
- 1986. 2308 hosts
- 1987. More network building. 28, 174 hosts
- 1990. More network building. Tim Berners-Lee at CERN built a hypertext system to serve the needs of a high energy physics group. 313,000 hosts
- 1991. T3 implemented (45 Mbps connection speed). 617,000 hosts
- 1992. Internet Society chartered. CERN releases the World Wide Web (the beginnings of the WWW). 1,136,000 hosts
- 1993. Mosaic for X was released as a graphical interface for the WWW. The WWW was about to go mainstream. 2,056,000 hosts
- 1994. First commercial ventures on the internet. 3,864,000 hosts
- 1995. Domain fees introduced. 6,642,000 hosts
- 1996. 15,000,000 hosts
- 2000. 93,047,785 hosts
- 2001. 125,888,197 hosts
- 2002. 162,128,493 hosts
- 2003. 171,638,297 hosts (as of January, 2003)
To get an idea (or many ideas) of how the internet is structured, check this site
The WWW
The world wide web refers to the graphical overlay that has been built onto the internet. It depends on the interconnectedness of the internet. Each computer is autonomous, and is identified by an address. Computers on the internet can be divided into two basic functions - servers and clients.
Servers are computers that supply information. To be a server, a computer needs to run specific software that can accept incoming requests and respond with the appropriate information. Most commonly these days, this is web server software such as the Apache web server software used on Unix and Linux computers, or Microsoft's Internet Information Server (IIS) which you can run on your computer.
Clients are computers that get information. To be a client, a computer needs to run a piece of software that can communicate across the internet with the server. The web browser is exactly that. It can connect to any web server on any computer on the internet and request information. The information is returned in the browser.
A computer can be both a server and a client. The machine used to build this course is running IIS and is a web server. It is also used as a web client, with many web searches conduced each day using search tools such as Copernicus and Google. Web browsers used are Internet Explorer and Mozilla's Firebird.
The WWW has many forms of information served by a variety of servers and accessed by a variety of clients. For example, streaming audio, streaming video, instant messaging (AIM, MSN, AOL, Yahoo), and email require both servers and clients.
Most home computers on the web connect through an internet service provider (ISP).
Figure Connections to the Internet
The computer connects through a dial-up modem, or an always-on Digital Subscriber Line Modem (phone company) or Cable Modem (cable company). The ISP (Internet Service Provider) Router (a special type of computer) provides access to the internet. There is constant communication back and forth between the ISP router and your computer.
The Protocols
The internet is based on the fact that data can be recorded as bits (0s and 1s) of information, the bits can be grouped as packets, and the packets can be sent using TCP/IP protocols. Packets have a wrapper of addressing information (sort of like an envelop with an address on it) which routers (special computers that act as collection/distribution points for packets) use to send the packet on to its destination.
The packet's destination is a computer address. Addresses are a IP protocol used to uniquely identify a computer on the internet, exactly as you street address identifies your house. The IP address takes the form
nnn.nnn.nnn.nnn
where nnn can be any number from 000 to 255 for a total of 256 possible numbers. For example, STEM~Net's IP address is 134.153.233.1
The different parts of the IP address have special designation. In simplest terms, the last set of 3 digits specify the computer, and the first 3 sets of 3 digits specify the network. So 134.153.233 is used to locate STEM~Net on the internet, and the .1 at the end locates the actual computer at STEM~Net that is acting as the server.
DNS (Domain Name Server) is a method of keeping track of all the computers on the internet. The DNS service makes a connection between a domain name such as www.cdli.ca and its IP address of 134.153.233.1 by storing both of them in a lookup table. All domain names are associated in this way with IP addresses and are stored on many different DNS servers around the world. When you set up your computer for an internet connection, your ISP will give you one or more DNS IP addresses to use.
WWW protocols are used to identify the type of server connection you are seeking. The web browser looks uses a URL (Universal Resource Locator) address to connect to a web site. The URL is basically the domain name (or IP address) plus the location of the file on the server. The SchoolNet News Newsroom page is located at http://www.snn-rdr.ca/snn/news.html
www.snn-rdr.ca is the server address
/snn gives the path to the folder the file is stored in
/news.html is the file that you will load on your screen when you open the page
You probably noticed an http:// at the beginning of the URL. This tells the browser that the file you are asking for is in hypertext transport protocol (a web page). Other protocols include ftp:// (file transfer protocol), https:// (encrypted web page), news:// (usenet news), telnet:// , gopher:// (the first graphical internet protocol) and file:/// (a location on your computer - try opening a file on your computer into the browser)
Activity
Assigned activities
Using your web browser and the Google search engine (http://www.google.com), investigate the types of url protocols that are available.
Test Yourself
There is no self test for this lesson.