Ian McDonald wrote:

Hmmm... RFC2988 says:
   (2.4) Whenever RTO is computed, if it is less than 1 second then the
         RTO SHOULD be rounded up to 1 second.

         Traditionally, TCP implementations use coarse grain clocks to
         measure the RTT and trigger the RTO, which imposes a large
         minimum value on the RTO.  Research suggests that a large
         minimum RTO is needed to keep TCP conservative and avoid
         spurious retransmissions [AP99].  Therefore, this
         specification requires a large minimum RTO as a conservative
         approach, while at the same time acknowledging that at some
         future point, research may show that a smaller minimum RTO is
         acceptable or superior.

I went and had a look and this RFC has not been obsoleted. RFC3390
also backs this assertion up.

So I'm suspecting that the default should be changed to 1000 to match
the RFC which would solve this issue. I note that the RFC is a SHOULD
rather than a MUST. I had a quick look around and not sure why Linux
overrides the RFC on this one.

If nothing else, 200 ms is a "principle of least surprise" thing since 
that is the current value (in MS) for TCP_RTO_MIN.

rick jones