The collection of communication lines and routers form the subnet.When a packet is sent from 1 router to another via 1 or more intermediate routers,the packet is received at each intermediate router in its entirety, stored until required output line is free and then forwarded.A subnet organized according to this principal is called a store and forward packet switched subnet.
When packet are small and all the same size,they are often called cells.
Packet travelling bearing number in the sequence.
Not all WANs are packet switched. A second possibility for a WAN is a satellite system.
Each router has an antenna through which it can send and receive.All routers can hear the output from satellites.
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