The Internet
History -- UUCP- the first program that ran on the Internet. Fidal Net- the government redundant communication system. Arpanet- a communication system designed by the US Defense Department. They wanted to design a computer network that was indestructible. They wanted to have a system where machines of different types can communicate with each other. Thus, if part of the network was destroyed, the surviving parts automatically reroute communications through different pathways.
Local area networks proliferated in universities, starting with CUNY schools. CUNY was the first who employed the centralization technique.
In the late 1980s the National Science Foundation built five supercomputer centers to give academic researchers access to high-power computers formerly only available to the military. The NSF built its own network, based on IP technology, to connect the five regional centers together. Individual university networks were chained together and linked to the closest regional center. NSFnet emerged. CUNY schools used Nysernet which employed the TCP/IP protocol.
Moral/Ethical Issues -- When we talk about the ethics of the Internet issues such as privacy, copyright laws, intellectual property, spaming, electronic stalking, come up. Protection of copyrighted material is a problem anyone can download data from the Internet. E-mail security is another problem. You never know who might break into your e-mail account and if this does happen you may be bombarded by junk mail and even some obscene mail To protect their internal resources against outside intrusions, most businesses set up a "firewall", a stand-alone computer that allows you to control all incoming and outgoing Internet communications.
Connecting to the Internet
There are four major ways to access the Intenet:
Dedicated line -- You can access a router which is a device that routes packets from one subnetwork to another. A bridge is a connection between two local area networks and it's usually done withe a PC as the bridge in between. Packets are sent on their way. They don't travel on the same route because there are many different ways to get from place to place. It's the router's job to reassemble the packets when they reach their destination. The Digital Voice combines voice and data and digital systems. POTS is a plain old telephone system. It has to convert digital to analogue and analogue to digital.
Dial-up Access (terminal account) -- Your local machine becomes a terminal or window into a machine that is hooked up to the Internet. The advantage is that it's fast because nothing is running on your machine, but the disadvantage is that you're stuck with whatever software is on their machine.
Dial-up Access (using a permanent PPP connection) -- You have and IP number and it's permanent.
Dial-up Access (using a temporary PPP connection) -- Virtual connection on the Intenet so the host machine assigns you a way onto the Internet.
The PC makes a connection to LAN via a modem or direct wire. Then the host network makes a connection to another line to a separate network . A router inspects your request and based on available connections the router determines the best path to take. As the request passes from network to network a set of protocols create packets. Packets contain the data itself as well as the address, error checking, and other information to make sure that the request arrives at its destination. When the request reaches its destination, the packets are read. The remote computer than takes the appropriate action such as running a program, sending data back to your PC, etc
Protocols
TCP - a protocol that organizes packets, manages their transmission, and ensures their accurate delivery to the receiving station.
IP - Internet Protocol that manages packets between stations on the same or different networks. Networks use a variety of communications and operating systems, networks cannot talk directly to one another. To help this problem a router is used. When a message is received the router performs the necessary protocol conversion and routes the message to its destination. A backbone is composed of one or more routes and the associated transmission media that links the routers and the mainframe computers within the system networks.
The addressing scheme directs the packet to its location. Static IP address is usually temporary, its usually used with AOL, CompuServe, etc.
Searching The Internet
Archie - file searcher. It's a software program that finds a particular file that you are looking for and using an FTP server it downloads it.
Gopher - a search tool that searches through many archie servers, looks through topics and gives you information in menu system like a table of contents.
Veronica - Very Easy Rodent-Oriented Netwide Index to Computerized Archives- searches for gophers.
Yahoo - A catalog site.
Infoseek - A non-catalogue site.
Cookies
Cookies - are a small little file that contains information about your machine. (e.g. your most frequently visited sites) When you use your browser the cookies are loaded into memory, and if you return to a site that set a cookie, the web server can recognize your server and return specific information based on your preferences.
Java vs ActiveX
The advantages of Windows is that it makes programs independent of the computer's hardware. The API (Application Program Interface) interacts with the underlying OS. Microsoft distributes the SDK (Software Development Kit) so the programmer does not have to worry about low level interactions. In addition, the MFC (Microsoft Foundation Class) creates objects (window, mouse, etc.). Microsoft allows programmers to put together a program by clicking on buttons and building out of pre-fab pieces (COM model). The program will only require few lines of code.
Programmers want to be able to run components that will run on any machine, especially with the boom of the Internet. There are different approaches:
1. Write programs for each machine.
2. Make the new machine act like the old machine by putting two boards on it.
3. Apple developed a system called the P-system. They wanted Pascal to be able to run on the Apple, so they developed a fake language called P-code and wrote a compiler that translated Pascal to P-code. If you write a P-machine simulator for any machine, any program written for the P-system will work on any machine and you do not have to rewrite the code.
Java - Sun wants to write a language that will run on any machine as well. So they developed Java. 1. Java follows Object Oriented programming. It is similar to C/C++, but leaves out unnecessary components of C++. 2. Java offers security against viruses. You can write full blown applications that have access to your computer, or you can write applets which can only run in the browser. It has no ability to read or write to the disk. Applets play in the sandbox (cannot harm your computer). 3. Programs running in Java run in the Java Virtual Machine. it's like the P-system. The compiler turns the program into byte code that can run on the Java VM. One program can run on any machine as long as it has the VM and Java will be the underlying system.
Java uses an interpreter - it interprets the code one line at a time, during run time. (As opposed to a compiler which compiles the entire program at once).
ActiveX - In a world of pure, if your given all the components you want, you can write programs that will run in browsers. It follows Object Oriented methodology. It is not secure (does not play in the sandbox). If you want to view a page, you should check if it has a certificate from Microsoft that it is safe. ActiveX is more powerful than Java.
Video Conferencing
With Video Conferencing, you call the IP directly. It is point to point. The transfer rate is 8 frames per second which isn't very smooth. This delay is caused by Internet speeds. The video is captured by a video capture board or by a camera that goes into the parallel port. The camera can ideally film at 30 frames per second.
During a video conference a reflector is used by the server. The problem with TCP/IP is that packets only contain one address. Multicasting is needed. Instead of sending multiple screens to multiple people, you want to send one packet to everyone. A different protocol is needed in order to have multicasting features.
News Groups
News servers are like e-mail, but you don't send the message to individuals. Rather, messages are posted to a board. It works in a client server relationship. Newsgroups are organized into hierarchies. there are sanctioned groups (like rec, soc, sci, etc.). Alt groups are unsanctioned. New groups are always created. If the group is officially sanctioned, it will appear on most news servers. When you subscribe to a newsgroup, the headers are updated.
Messages are organized by date and threads (replies). Spamming means sending junk/irrelevant e-mail It is considered a culturally bad thing on the Internet.