Total bandwidth utilization on a full-duplex port

Unanswered Question
Jun 4th, 2010

My co-worker and I are having a disgreement over this question and perhaps someone can help us settle it.  Here's the question:

On a 100 Mbps full-duplex port, is the total, aggregated bandwidth 100 Mbps or 200 Mbps?  I think it's 200 Mbps: 100 Mbps TX and 100 Mbps RX.  For example, see the following output from a full-duplex, 100 Mbps interface:

5 minute input rate 4332000 bits/sec, 536 packets/sec

5 minute output rate 31979000 bits/sec, 3100 packets/sec

On this interfaces, the RX (input) channel shows about 4.3 Mbps, while the TX (output) channel shows about 31.9 Mbps.  According to my aggregated 200 Mbps theory, the RX is only 4.3% utilized and the TX is 31.9% utilized.  My co-worker, on the other hand, says that he adds the two figures up to determine interface utilization, so for this example, he would consider this interface about 36% utilized.

I think I'm correct, because after all, isn't that the whole idea of full-duplex, that you get bi-directional throughput?  I just need some verification so I can throw it back in his face and declare victory...


I have this problem too.
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