Need for IP address

Question

Why do we need an IP address when the MAC address is unique? Cant we communicate only with the MAC address?

Answer 1

You COULD communicate using only the MAC address, but only on your local network. IP addresses are routeable, without every system on the network needing to know about every other. You just need to know a range of addresses that are on your local network, and throw everything else up to your router. The same thing happens at the ISP level. "All 216.x.x.x traffic goes that way, all 105.x.x.x goes that way..."(Obviously a gross oversimplification, but that's the basic process).

If we tried to route everything by MAC address, every machine on the network would have to maintain a list of every other participant, and it just wouldn't scale.