perfSONAR User Q&A and Other Discussion

[Brian Candler <>]

On 21/06/2016 09:31, Garnizov, Ivan (RRZE) wrote:
> Here are my 50 cents in this interesting thread.
> It is not necessary to see retransmits in cases where a congestion management is 
> applied (as Brian referred to it "smaller buffer").
> He pointed that this is a pattern for an intermediate device being 
> overwhelmed. That alone suggests that on one side of the connection there is 
> a router, which on a certain threshold starts sending flow control messages 
> to the toolkit to slow down. This does not even mean the router is 
> overwhelmed with traffic. It means the router sees the possibility of being 
> congested and immediately sends control messages to one party to reduce the 
> size of the window.
By "flow control messages" do you mean TCP ECN? (As opposed to, say, 
ICMP source quench, or ethernet flow control, or some other mechanism)

ECN is a possibility. However it doesn't explain why the OP was able to 
overcome the limit by using the -w flag to set a different window size.