The purpose of routing may not seem obvious. The question arises, "Why not put all computers onto the same physical layer 2 network?" The answer is, "Try it." Ignoring the different connection type issue, let's do the math for the Internet, which is nothing more than a big network. If there are a meager 6,000,000 computers on the Internet all connected to each other through 100Mbps connections (and a whole bunch of switches), then let us take a look at some of the procedures. For example, let us look at a simple broadcast packet that is used very often: ARP. When a computer sends out an ARP packet, then all other computers in the entire world will receive that ARP and one will respond. So at maybe an average of 1 ARP/minute/computer, each being 64 bytes, we get 6.1MB/s of sustained traffic over the whole network taken up by just ARP traffic. Another theoretical 6MB/s are left for all other communication. (What if there are 60,000,000 computers?) Or in a different situation, let's say there's one person who thinks, "Let's see what happens if I send out broadcast packets at the full 100Mbit/s." Now, these broadcast packets get sent to each and every computer. That would mean that just this one person is taking up all bandwidth available. Needless to say, there needs to be a better way of doing this.