There is hardly a business on the planet that doesn’t have a firewall nowadays. But a firewall ensures, for example, that someone can access your website but can’t use Remote Desktop to log into your web server, because port 80 is open and port 3389 is not. Without a firewall, everyone in the world could access your servers on every possible port (of which there are 65,535). It improves security by allowing you to specify rules about which packets are allowed in or out, based on the IP address they came from, their destination IP address, and the port number. If the browser were to have requested the page via port 90, the web server would never see it.Ī firewall, at the simplest level, is a system (hardware or software, or both) that logically sits between one or more computers and their connection to the Internet. The server, which knows to listen for requests on port 80, receives the request and sends back the required page. In reality, all the data goes down the same cables, but the packets also contain the port number so that the receiving computer knows what to do with the data when it arrives.Ī web browser sends a request on port 80 to the server that holds the page it wants. Email messages travel between senders, email servers and receivers via port 25. On the Internet, a web server communicates with a visitor’s browser using port 80. Think of it as a TV receiving sports on channel 9 and documentaries on channel 3. TCP/IP uses the concept of ports, or port numbers, to differentiate different types of traffic.
And because each packet also contains details of the destination IP address and a sequence number, everything will get to the right place eventually. To send more than 500 bytes you simply send multiple packets. Amazingly, the answer was not necessarily a foregone conclusion.ĭata travels over the Internet in chunks known as packets, typically around 500 bytes long, using a system or protocol called TCP/IP. It’s hard to believe that in the early days of the Internet, computer magazines aimed at enterprise IT users would carry articles with titles such as “Does Your Company Really Need a Firewall?”. Forms, social media postings, bookings and payments, email messages, and more. We can allow the world to send us information back. We can connect a server to the Internet, load it with documents and images, databases and web pages, or carefully-written applications, and instantly make its contents available to the world. A firewall is a system that logically sits between one or more computers and their connection to the Internet.Īs an enabling technology for quick, easy and cost-effective dissemination of information, the Internet is an incredible tool for an IT person to have at their fingertips.
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