> Doesn't the text mean that if the loss is at the right edge, the
> next recourse is an RTO and rxt, because the left edge sourcing is
> stopped because the window is full?
I don't think so. But, I am confused by what "the window" means at
this point. Congestion or advertised?
An example... Say we send segment 1-8 and segment 8 is lost (the
right edge). Now suppose we get ACKs for packets 2, 4, 6 and 7 (as
would be reasonable with delayed ACKs and no ACK loss). The ACK for
segment 2 would clock out packets 9 and 10 (assuming we're in
congestion avoidance here). The remaining ACKs clock out packets
11-15. When these data segments arrive at the receiver they all
trigger duplicate ACKs that cover everything through segment 7. In
the case of limited transmit we would clock out segments 16 and 17
on the first two dup ACKs. But, in either case we are going to end
up getting the required three dup ACKs to trigger fast retransmit --
*unless* there is lots more data/ACK loss such that 3 dup ACKs will
not arrive.
So, I do not believe the position of the loss within the window has
much bearing on the effectiveness of limited transmit. Rather, the
size of the cwnd and the amount of loss are the keys, I think.
If you mean that we lose something at the left edge of the
advertised window limited transmit doesn't buy you anything either,
because the algorithm still can't violate the receiver's advertised
window.
Does this make sense?
allman
--- Mark Allman -- BBN/NASA GRC -- http://roland.grc.nasa.gov/~mallman/
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