If you look on the far system it's receive window will be doing the same
thing. The Send window must match up with the receive window. Much like
a trucking company can't send a truck with a 53ft trailer to a company
with room for only a 28 footer. Doing so it would be turned away.
So the connection must be quite busy or the receiving system is busy.
Until the data is transferred out of the receive buffer to the
application the space isn't available and if buffer space is filling
then it begins to 'close the window'. It's very wasteful to send data
that gets dumped (and thus must be resent) due to no buffer space (just
like the trucker!) so the window gets lowered to account for that.
Unfortunately in an effort to be efficient sometimes dispatchers don't
call the customer and send the wrong truck. And with TCP sometimes the
TCP receiver tells the sender "Got your data" so the sender can send
more but the sender can't get the data out of the buffer to the
Application in time so the new inbound data gets dropped. This causes
retransmissions. (Other things do too like actual communications errors.)
- Larry "DrFranken" Bolhuis
On 10/18/2013 6:11 AM, Sam_L wrote:
Looking with NETSTAT, option 3, I see under "Send window information"
that the Maximum size is 262144 and the Current size is somewhat lower,
fluctuating, 252568, 256672, 253936, etc.
The Total retransmissions is going up about 1 per second.
This is a Mimix remote journal over a VPN to a backup site in another
state. The network folk tell me that there is an internet segment.
Right now there is a lot of data being pushed through it.
Most of the time the Current window size is also 262144 and when it is
there are no retransmissions and Mimix doesn't get behind.
The network guys are not clear what a "Send Window" is. Can anyone offer
any clarification or suggestions?
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