Internet Protocol (IP) Address

Every computing device on a network must have a unique IP address for each connection. The IP address works the way a real address works - any data packet sent to the remote computer carries with it the IP addresses of the source and destination computers. These addresses are used to send the packet of data to the right place. In general, data on a wire 'hops' all the way to the remote destination. Sets of wires carrying data are connected to routers. Routers contain tables that map destination IPs to 'Ports' - a port on a router is a sort of channel that directs the packet to a wire that leads out of the router. The router reads the IP address on a packet and sends it onto the right wire on its next hop towards the destination. This goes on until the destination WAN is reached and the packet, on its last hop, jumps to the destination computer. Without an IP address, dat would be lost.

Fig 1c: How a router sends data on its way

IP addresses may be static or dynamic. A static IP address is permanent. Large domains, servers, ISPs, and Proxy Servers have static IP addresses. A dynamic IP address is temporary and assigned to computers that connect to the Internet every now and then. Once the user ends the Internet session by disconnecting or turning off his modem, the temporary IP Address assigned to him is assigned to someone else. If you are connected to the Internet, you can check your IP address by doing the following:

1. Check IP Address Using Windows
2. Select 'run' from the Start Menu
3. Type 'cmd' in the pop-up window next to Open: and click on the 'OK' button. A window that looks like the one in the following screenshot will appear.
4. Type 'ipconfig' at the prompt and hit enter
5. You will get a listing of your IP address

Screen Shot 1a: Check IP Address using 'ipconfig'

IP addresses take the "dotted decimal" form. They are identified by four sets of numbers separated by periods, e.g., 208.161.72.1. The IP address of a web site will bring up the web site just like the name of the web site. IP addresses use a 32 bit number that identifies both the host computer and its network. Valid IP addresses are running out fast, the next version of the IP protocol will unveil a virtually unlimited number of IP addresses. IP addresses may be class A (first digits in range 1-126), Class B (first digits in range 127-191), or Class C (first digits in range 192-223). This classification has to do with the maximum number of hosts and networks that an IP Address can accommodate.