> If all addresses were based on mac, you could easily intercept the messages from anyone.
So you encrypt stuff you don't want anyone else to read. Security isn't the concern of the networking layers; it's all done, to the extent it is done, at the application layer.
That's the original design, anyway.
Edited to add: Well, the original original designs were by people who weren't thinking of security at all. That's why telnet and FTP are the way they are.
> Another problem is that numerous devices will share the same MAC address, it's just statistically unlikely to find them on the same network.
This, on the other hand, really is a perversion of the intended model. 48 bits was intended to be globally unique.
>it's all done, to the extent it is done, at the application layer.
Sometimes true but often not. Encryption can and does happen at various layers of the (OSI) networking stack (Secure Session Layer, Transport Layer Security, Internet Protocol Security).
>That's why telnet and FTP are the way they are.
Those programs are the way they are due to a holdover from the Unix philosophy: do one thing and do it well. Sure, functioning at all was more important than functioning securely. If you ran your connections over a VPN, SSL or IPSec line, the fact that telnet didn't also support encryption would be moot.
The Application layer is for the applications data. If you want to secure the transmission of that data, it shouldn't be up to each and every individual application to support encryption.
This is why things like IPv6 or SPDY/HTTP2 have baked-in encryption below the application layer.
So you encrypt stuff you don't want anyone else to read. Security isn't the concern of the networking layers; it's all done, to the extent it is done, at the application layer.
That's the original design, anyway.
Edited to add: Well, the original original designs were by people who weren't thinking of security at all. That's why telnet and FTP are the way they are.
> Another problem is that numerous devices will share the same MAC address, it's just statistically unlikely to find them on the same network.
This, on the other hand, really is a perversion of the intended model. 48 bits was intended to be globally unique.