hi,

when doing unidirectional tcp bulk transfer,
i observed more than 2 acks per 3 segments.
it was more than i expected (1 ack per 2 segment).

it seems that additional acks are for window updates.
tcp_output sends a window update whenever it opens the window
by more than 2 segments.

a question is: what's a rationale of this?
it looks too frequent to me, given that
"an ack for at least every second segment" is
already achieved by TCP_SETUP_ACK.

YAMAMOTO Takashi