From: gah@ugcs.caltech.edu   
      
   rmbandes@gmail.com wrote:   
   > I believe these statements to be true, mostly from reading RFC 791:   
      
   > 1) You may put data in the SYN and SYN+ACK segments, but it   
   >    doesn't make any sense since the TCP connection isn't   
   >    established yet.   
      
   In a non-interactive session, I might already know what I want to ask.   
      
   > 2) You may put data in the ACK segment which acknowledges the SYN+ACK.   
      
   > 3) I'm not sure if the ACK acknowledging the SYN+ACK can carry   
   >    the FIN flag, but I can't find any prohibition for it.   
      
   > 4) The TCP state diagram in RFC 791 makes it look like you can't have   
   >    a FIN flag in the ACK segment that acknowledges a FIN segment.   
   >    I believe this is because the diagram is documented as   
   >    being incomplete.   
      
   > So I believe that the shortest (in segments, not bytes or time)   
   > TCP connection is as follows:   
      
   > Client <-> Server   
   > -> SYN   
   > <- ACK, SYN   
   > -> ACK, data, FIN   
   > <- ACK, data, FIN   
   > -> ACK   
      
   It is possible that some sessions will have a data length of zero, in   
   at least one direction. I time server can always return the time,   
   without any incoming data. (Which it seems could be on the syn-ack.)   
      
      
   (snip)   
   >> > On Sat, 2013-01-19, glen herrmannsfeldt wrote:   
      
   >> >> Can you add data to the SYN, SYN+ACK, and ACK packets   
   >> >> of the three-way handshake?   
      
   >> >> Can you add FIN on the last (and first) data packet?   
   >> >> That is, does:   
   >> >> 1)  SYN+data+FIN   
   >> >> 2)  SYN+ACK+data+FIN   
   >> >> 3)  ACK   
   >> >> work?   
      
   (snip, I also wrote)   
      
   >> Probably it should be two separate questions.   
   >> First about data on the SYN and SYN+ACK, and second on   
   >> putting FIN on the SYN and SYN+ACK.   
      
   Note that was over a year ago!   
      
   -- glen   
      
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