The Device That Built The Internet
The Device That Built The Internet
We take our technological world so much for granted, and we seem to forget all of the things that make it work. The protocols that scaled the Internet have been ARP, IP, TCP, and UDP, along with the application layer protocols (HTTP, FTP, TELNET and so on). But the device that has really built the Internet is the humble router.
The idea behind the router was created by Sandra Lerner and Leonard Bosack, and who were working in the computer department at Stanford. After the university effectively dismissed it for commercialisation, in 1984, they went ahead and founded Cisco Systems Inc. Their first router product went live in 1986, and within a year they had sales of around $250,000 per month. The company have never looked back since then.
So, what is a router? Well, it does what it says on the tin … it routes data packets. Basically, it has a routing table and a number of interfaces. When a packet arrives on one of the interfaces, the router examines it, and then looks into its routing table, and decides whether it needs to forward the data packet to another of its interfaces. In this way, routers pass packets from one device to another. If we route for IP addresses, we define this as Layer 3 routing. We can also route data frames within a switch, and which is known as Layer 2 switching.
Obviously, routers can only see other devices to which they can connect to, so each of them communicates with each other and pass on information on how to get to destinations. In the simple measure, we define the forwarding from one interface to another as a “hop”. We can thus find the best route to a destination, by finding the route with the least hops. This leads to a routing protocol named RIP (Routing Information Protocol). Obviously, the least hops might not be the best measure of the quickness of the route or its reliability, so we can get other routing protocols that can take these things into account. Common routing protocols which have alternative metrics to hops include IGRP (Interior Gateway Routing Protocol) and BGP (Border Gateway Protocol).
With the Internet, we can either have a public IP address, or private IP address. Routers pass information between themselves on the best way to get to a destination network. We can thus merge addresses together and generalise them with a subnet (or sub network). The subnet is defines a whole network segment, and it is these addresses that routers use to store a destination. The subnet mask is then set on a host, and will generally define the scope of the network that it can directly communicate with. In order for data to get out of a network, the host needs to connect to a gateway, and which is normally an interface on a router.
Here’s a quick demo of setting up some simple details:
And so, I’ve created a few pages for you to investigate these magical devices: