From: John Heffner <redacted>
Date: Tue, 08 Jan 2008 23:27:08 -0500

I also wonder how much of a problem this is (for now, with window sizes 
of order 10000 packets.  My understanding is that the biggest problems 
arise from O(N^2) time for recovery because every ack was expensive. 
Have current tests shown the final ack to be a major source of problems?

Yes, several people have reported this.

It's a real issue, and it's only going to get worse.