M. A. Padlipsky
Mitre-Bedford
November 1985
Mitre-Bedford
November 1985
TCP-4 Prime
STATUS OF THIS MEMO
-
This memo continues the discussion of a possible transaction oriented transport protocol. This memo does not propose a standard. Distribution of this memo is unlimited.
DISCUSSION
In response to Bob Braden's call for a transaction oriented
protocol (RFC-955), the following thoughts come to mind:
o The perceived problem is that connection set-up and tear-down
take too long.
o Other aspects of TCP's reliability/robustness approach are
presumably still desirable.
o We have some spare command bits in the TCP header, and I trust
that there's still a version number field.
o So why not add NYS (no-way handshake) and NIF (graceless close)
commands to TCP and leave everything else as was (except for the
version, of course)?
Philosophically, that might be somewhat at variance with "the spirit of
TCP," but pragmatically it ought to do the trick. Some careful crafting
might be required for ISN handling with NYS, but my guess is that if you
have to resend the first/possibly only segment you just pretend you're
all of a sudden in the middle of SN space (initially you start at the
bottom of it) and when it sees the funny ISN the NYS handler knows it
should dequeue anything it might have had pending for (re)transmission
and start fresh, assuming that if anything gets through to the starting
side belatedly it'll get chucked because of being well outside the left
edge of the window, if I'm remembering that part right--and please be
aware that I'm not bothering to confirm recollections because I don't
want to pretend that this is the spec: it's just meant to be the
concept, in TV talk. (On the NYS emitting side, presumably you just
drop right into ack_expected state--or whatever the right name is--after
setting an appropriate bit that'll get you to fiddle the ISN if you take
a timeout.) Maybe you even fiddle the ISNs more elaborately, to allow
for several false starts rather than "two strikes and you're out," and
maybe we take some spurious segment hits if SNs get suitably balled up,
but if you really think handshaking is too expensive then that's the way
the premise crumbles.