Multiplexing

Multiplexing

1. Carrying several different connections over a common link

   • Useful because long distance cables are expensive and need to be shared.

2. Time-Division Multiplexing (TDM)

   • If a stream has nothing to send, its time slot is wasted
   • Doesn't require data frames to carry a stream identifier
   • Uses Fixed Time Slots
     • So each bit stream gets a fair share of channel

3. Statistical Multiplexing

   • Doesn't use fixed time slots
   • If A has more to send than B, it will use more of the available time
   • If a stream has nothing to send, another stream can use the channel
   • Data frames MUST carry a stream identifier
   • Design must make sure that all bit streams get a fair share when the load is heavy