'the impact of sending large data using tcp protocol
can someone explain why a TCP sender might automatically slow down when sending a large file? I understand that one reason could be the increased packet volume from the large data file, which would increase wait time and increase ACKS.
I was thinking that a second reason could be that the data caused a timeout, and following a timeout the cwnd is set to 1. If this second explanation is wrong could someone explain another reason for me?
Solution 1:[1]
The high level answer is that there is a saturation effect.
The most likely low level cause of this would be that the receiver, via the TCP protocol, is indicating its Receive Queue (Recv-Q) is full. This typically happens when the Userspace application is not ingesting the data as fast as it is being sent. This causes a traffic jam on the sender's Send Queue (Send-Q) as well. Both of these queues/buffers are in the operating system and can be examined with netstat or the more modern ss commands. The more exact ss command would look like: ss -tn state established.
That being said other saturation effects are possible. If there is a throughput bottleneck somewhere, and you could be contesting with other application for throughput. The longer you hog the channel the higher the chance of contention. This would likely show in a high Send-Q but a low Recv-Q.
Sources
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Source: Stack Overflow
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