[e2e] TCP retransmissions at end of data stream

[Agthorr]

Hello,

I'm a graduate student at the University of Oregon.  I'm working on a
packet-level simulator (derived from ns-1.4) for a peer-to-peer
application.  I've encountered a glitch in my NewReno TCP
implementation that causes performance problems.  I can think of some
ways to fix it, but I'm wondering if there is a standardized way to
handle this case.  My advisor, Daniel Zappala, suggested this mailing
list might be a good place to ask.

The problem occurs when there is packet loss at the end of the data
stream.  For example, if the server only has 8 more packets of data to
send, and they are all lost.  Since there is no more data to send, the
receiver will not generate any duplicate ACKs, and the sender
eventually times out.  The sender retransmits the first lost packet,
and the receiver ACKs it.  What happens next?

Right now, in my implementation, the sender times out again and
retransmits the second lost packet, with exponential backoff.
Needless to say, this makes transmitting those last few packets
extremely slow.  What should my implementation be doing?  Is this
documented anywhere?

-- Dan Stutzbach