1. M of router is short for Mbps, and bit rate is a unit used to describe the speed of data transmission. The greater the bit rate, the faster the data flow rate.

2. Theoretically, with a network speed of 15Mbps, the transmission speed per second is 18.75 MB/s.. With a network speed of 3Mbps, the transmission speed per second is 37.5 MB/s.

3. The data flow rate is variable, and the bit rate is only an average reference value. The network speed of 1M is 128KB/S in theory, but it is actually less than 12, because the data will be lost in the transmission process.

give an example.

in other words, the 15M marked on the router means that the router can only support a bandwidth of 15M at most. Even if the network speed is 2M, it will only come out of the router at 15M and 3M.