[e2e] How often does congestion control react upon loss?

Detlef Bosau detlef.bosau at web.de
Mon Jan 15 07:25:30 PST 2007

I apologize, if this is a beginner´s question.

During simulations with large buffers I often have several "drop bursts" 
when a buffer overruns because the RTT is quite large (due to the large 
buffers) and therefore it takes some time for a receiver to detect a drop.

Now I wonder (and I´m currently reading RFC 3517 to get this question 
answered but perhaps someone can help me here to understand this) 
whether it is possible to do several congestion actions in a round. To 
my understanding it is by all means possible (and makes sense) to get 
several sequence numbers in the scoreboard marked "lost" within a round. 
Of course, when a sequence number is marked lost, the sender has to 
retransmit the appropriate segment.

However, is the congestion window halved each time a sequence number is 
recognized as "lost"? Or is there a limit, e.g. the congestion window is 
halved only once a round?



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