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Short sequences (Re: An alternative to TCP (part 1))

2001-02-06 23:00:02
At 22:46 06/02/2001 -0500, Keith Moore wrote:
p.s. Personally I'm interested in a transport protocol for the other end
of the spectrum - something which has the order-preserving, duplicate
suppressing, and clean open and close properties of TCP but which can
exchange small amounts of data in one or two round trips,

One of the history lessons on this list about 6 months back referred to Dag Belsnes' original research proving that you cannot move a data item and end up with both parties knowing that the data has arrived safely in less than 5 packets. Other people have the referents....it's not obvious to me either.
It's probably this one from RFC 675's reference list, but to find it...?

 BELS74

      D. Belsnes, "Note on single message communication," INWG Protocol
      Note #3. September 1974.


(In TCP, the packets are the 3-way handshake and the FIN exchange)

T/TCP can achieve shorter packet sequences by leveraging knowledge from previous interchanges. You can get away with fewer exchanges if you are willing to (for instance) have the recipient not know whether the sender thinks the data has been transmitted safely, I think.

So there is a limit to what is achievable....



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Harald Tveit Alvestrand, alvestrand(_at_)cisco(_dot_)com
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Personal email: Harald(_at_)Alvestrand(_dot_)no