Can Throughput Exceed the Bandwidth of a Network? – Explained

Is it possible for the throughput to be greater than the bandwidth of the cable ?

Like many things, the devil is often in the details. Depending on how the measurement is taken, then yes it is possible. For instance, if you are using some sort of data compression and an application is measuring the amount of actual (uncompressed) data sent between two end points.

With no data compression, the same means of measuring can produce a lower throughput than the actual number of bits sent across the medium. This is because overhead (such as frame or packet headers for example) may not be counted.

Is it normal to have an average throughput of 10.401 Mbits/s on a cable of 10Mbits/s ?

In my experience, no it is not normal to expect compression on a network link. However it is fairly common for forms of compression to exist at higher levels of the OSI model, such as HTTP compression.

Yes, this is completely normal. And you use the minimum value of the calculations that you have done above. Think about how long it would take to move a box of paper down the hall - now imagine that you had to do it one page at a time. However, increasing the receive window is not always the answer. Sometimes the client makes small layer 7 requests (SMB does this a lot). So, a 64K TCP window won't help if client is only asking for 4KB blocks waiting for it to arrive then asking for the next one. You may also need to consider TCP slow-start in the equation.

Ok, now imagine you can carry multiple pages down the hall at a time, but you don't want to bring too many at a time. So you start with 3, if you don't drop any then next time you bring , then 8, then 13... Until you drop one, then you reduce by 50% and start ramping up again. That is TCP slow-start. And the count is called the CWND.

But none of that makes any difference because the win/rtt bw=800kb/s but the APP2 consumption rate is only 200 so that is the limiting factor.