There is a typo in description of 'setstreamthroughput' option. It is measured in megabits per second. Page with wrong description:
Page with right description:
Also I want to discuss possibility to reduce default value for this option. I think that 400 Mbs is too high for common cases.
This option is used only in case streams. There are two cases when streams are actual. They are rebuilding of a node and repair process. Let's skip first case and will talk only about the second. Let's imagine that we have replication factor 3.
Cross-datacenter connectivity case:
When we start repair process it will borrow all network channel. Let's do some calculations. You start repair on an one node, e.g. 5 node (3 remote and 2 local) should send us some data. Note that 3 of them are from remote datacenter. So 400 * 3 = 1,2 Gbs we should receive through WAN. I'm sure that it's too high.
I suggest to make it 2 times less.