How the Net Works A Very Brief Introduction We will talk about… What makes up the Internet How the WWW functions What is it? The Internet: “Everybody’s computers, connected.” A set of rules, or “protocols,” that allow different kinds of machines on different kinds of networks to talk to one another. The structures that emerge and are anticipated by these rules. What are some characteristics of the Internet? It is decentralized It is (generally) packet-switched It is hardware independent It (generally) uses client-server architectures Network Topology There is no center of the Internet There need not be a tree-like hierarchy In fact, there are central backbones that carry most of the internet traffic, but this is as much an economic as a technical characteristic. Packet-Switching Messages cut into sections of a standard size, affixed with a header explaining where they should be, and set out onto the net. This is very good for reliability. This is not-so-good for speed or efficiency. Traceroute programs allow you to seen how many bounces take place. Hardware independent A TCP/IP stack can be created for just about any computer/communication device. Just about anything can carry a TCP/IP message. Client-Server Architecture In most interactions on the net, one computer (yours!) acts as a client, while another acts as a server. The client requests a service, and the server delivers it. Simple, but important element of many applications on the Internet. Typical Web Request Client asks for the address of the host from a domain name server. It then sends a message to that address, attn. Port #80 usually, asking for a particular web page. The server sends the page and waits for another request. Internet Applications/Servers The TCP/IP Stack Ping Mail Usenet FTP Chat (IRC, ICQ) Web Others: DNS, Voice, Quake, Napster, etc.