My question is about the maximum bandwidth a switch\router can support for an entire network (not just 1 machine to another).
These pieces of equipment are often rated at 100 MBit, 1 GBit, etc. However they often have at least 4 ports if not more.
Quoting from Wikipedia:
An Ethernet switch operates at the data link layer of the OSI model to create a separate collision domain for each switch port. With four computers (e.g., A, B, C and D) on four switch ports, any pair (e.g. A and B) can transfer data back and forth while the other pair (e.g. C and D) also do so simultaneously, and the two conversations will not interfere with one another. In full duplex mode, these pairs can also overlap (e.g. A transmits to B, simultaneously B to C, and so on)
So if A is talking to B and C is talking to D at the same time through a 1 GBit switch, will each pair receive a 0.5 GBit connection or will each pair receive a 1 GBit connection? If each pair is receiving a 1 GBit connection, then the total network bandwidth at that time is 2 GBit and then seems dependent on the number of ports available on the router as well as the number of machine pairs on the network.