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« on: March 02, 2009, 01:12:45 AM » |
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Overview of Internet basics
How the internet works?
How does a computer know where other systems are on the Internet? An analogy can be drawn between the Internet and a phone system. As with a phone system, every house is represented by a unique number, so if you wish to place a call to a Mr. Tim, you need to know his phone number. In order to find his number, you need to look up his name in a phone number directory. Once you have found his phone number in a directory, you can place the call.
The Internet works in a similar fashion. Each computer (system) on the Internet must have a unique identifying number so that it can communicate with other systems and vise versa. In order for your system to figure out where “domain.com” is, it has to query an Internet directory so it can get the unique number (IP Address An IP Address is an identifier for a computer on a TCP/IP network. Networks using the TCP/IP protocol route messages based on the IP address of the destination. The format of an IP address is a 32-bit numeric address written as four numbers separated by periods. Each number can be zero to 255. For example, 123.456.789.1 could be an IP address.) for that server A server is a computer or device on a network that manages network resources. For example, a file server is a computer and storage device dedicated to storing files where any user on the network can store files. Servers are often dedicated, meaning that they perform no other tasks besides their server tasks. On multiprocessing operating systems, however, a single computer can execute several programs at once. A server in this case could refer to the program that is managing resources rather than the entire computer. or computer. These Internet directories are called nameservers (DNS Servers). Every system on the Internet needs to know the IP address of at least one nameserver if it wants to be able to resolve domain names to their respective IP addresses. If a system on the Internet isn’t configured with the IP address of a nameserver, it can still use the Internet but will not be able to “look up” a domain name.
How does a system know how to communicate with other systems on the Internet?
Once a system has the IP address of another system on the Internet that it wants to communicate with, it still doesn’t know how to send the information directly to that system, because it may be in another physical part of the world in a completely different network Network is a group of two or more computer systems linked together. There are many types of computer networks, including: local-area networks (LANs) wide-area networks (WANs), campus-area networks (CANs), metropolitan-area networks MANs), home-area networks (HANs). Computers on a network are sometimes called nodes. Computers and devices that allocate resources for a network are called servers. (group of computers/servers). In order for a system to know if another system is local or remote, a system must first know how to distinguish the two. When a system on the Internet gets its own IP address, it will also have a netmask (Network Mask) associated with the IP address. A netmask looks just like an IP, but is used as an IP filter, and when applied to the systems own IP address, it can tell if another IP is local or remote. If the computer is local, it just sends out the information directly to that IP address. If the computer is remote, it needs to send it to a system that will route (re-direct) the information to the final destination system on its behalf. These special systems are called gateways A gateways is a node on a network that serves as an entrance to another network. The gateway is the computer that routes the traffic from a workstation to the outside network that is serving the Web pages. In homes, the gateway is the ISP that connects the user to the internet. In business, the gateway node often acts as a proxy server and a firewall. (Gateways & Routers) because they are the gateway to the “outside world”. Every system on the Internet must have a gateway system configured so that it can get information out to other remote systems.
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