[e2e] Data + FIN

[Jitendra Padhye]

> > As to *how frequently* it happens, somebody with ready access
> > to packet traces can better answer that question.  Two years ago,
> > Anja Feldman gave me a number that was (I believe) on the order 
> > of 40% of TCP connection were doing this, based on a packet trace 
> > from AT&T.
> 

I have written a TBIT (http://www.aciri.org/tbit/) test to check this.  A
scan of about 10,000 web servers showed that web servers running Linux
2.0.35-37 (based on NMAP identification) are least likely to piggyback the
FIN on the last data packet. Overall, about 28% of the web servers did not
piggyback the FIN on the last data packet. There are a few caveats: 

a. The 10,000 web servers are from a trace taken at a web proxy, this is
not a representative sample in any way.

b. I set the MSS to 536 bytes. I wonder if the results will be different with
a different MSS. 

c. For each web server, I downloaded the base page (GET /). Unfortunately,
I did not keep track of the amount of data transferred. Richard's data
clearly indicates that this is important. 

- Jitu