As far as I know about full and half duplex, if we have a channel with bandwidth 10Mbps then in full duplex both sender and receiver can transfer 10Mb in both directions at the same time and in half duplex only sender or receiver can transfer 10Mb at a time.

If suppose, propagation delay is 1 sec then is the capacity of channel in full duplex 20Mb and in half duplex 10Mb ? How can the capacity of a channel double based on the mode, it should be same all the time right?

1 Answer 1


Think of a half-duplex connection as a single channel that you can turn around between packets. Then think of a full-duplex connection as two unidirectional channels that can be used simultaneously.

Physically, all modern twisted-pair or fiber Ethernet connections have two channels, one for sending, one for receiving (most prominent in 10BASE-T, 100BASE-TX and fiber). With half duplex they may not be used at the same time while with full duplex they may.

  • So in this case, the capacity is 20Mb in both cases, but in half duplex do we use only 10Mb out of it ? In full duplex is the capacity divided by 2 ? I mean 10Mb in one direction and 10Mb in opposite direction?
    – Zephyr
    Commented Jul 1, 2017 at 17:01
  • 1
    Each channel has the capacity of 10 Mbit/s. If you can only use one at a time, the total capacity is 10 Mbit/s. If you can use both it's aggregate 20 Mbit/s.
    – Zac67
    Commented Jul 1, 2017 at 17:20

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