What does Cisco mean by their Serial Interface?

Question

Cisco

What does he look like in reality? When is it applied? Why not use regular fastEthernet?

Answer 1

The serial interface is most often a synchronous serial interface with a speed of 2Mbps in both directions. It used to be used to connect various xDSL modems (there were such. Agate), ISDN converters. It differs from the usual (asynchronous) serial port of a computer in that communication through it is guaranteed, since both sides synchronize the "clock" at the time of the connection and constantly support the carrier.