> just to be fair, I have certainly seen Solaris accept out of spec behaviour in
> order to work with vendor XYZ's product.  
> [as an example, HPUX TCP/NFS client sends data on the final ACK of the three
> way handshake; didn't bother Solaris, but left my company's box rather
> frazzled]

It also help to read the spec before declaring something "out of spec".

RFC793 (the TCP spec) is quite clear that it's legitimate to include
data with the three way handshake:

  Several examples of connection initiation follow.  Although these
  examples do not show connection synchronization using data-carrying
  segments, this is perfectly legitimate, so long as the receiving TCP
  doesn't deliver the data to the user until it is clear the data is
  valid (i.e., the data must be buffered at the receiver until the
  connection reaches the ESTABLISHED state).  

Including it on the 3rd packet of the 3WHS doesn't require any unusual
buffering as the connection is in ESTABLISHED on the sender, and is
transitioning from SYN_RECEIVED to ESTABLISHED on the receiver.

					- Bill