Re: host down (was ..."layering violations")

Michael Padlipsky (PADLIPSKY@A.ISI.EDU)
Thu 12 Nov 87 12:33:54-EST

Since you asked....

"TCP", per se (or "TCP The Protocol"), doesn't take an explicit stand
on when to give up that I recall. I emphatically agree with you (and
Phil Karn, who started the subtopic off, and Mitchell Tasman, who pointed
out that there are extra pitfalls in the X.25 environment [which I was
not, repeat not, addressing in my first msg on the subtopic]) that it's
contrary to the robustness goal of TCP to give up too easily. I still
would hope that implementers to whom that view is a revelation don't
swing too far the other way and keep "obviously" shot connections
around needlessly, since in some contexts the storage shouldn't be
wasted and in other contexts (perhaps even in all contexts) there's
a waste of transmissions to get SNs back in synchrony. The call, however
forlorn, is just to "do it right"--and when you get right down to it, the
liabilities of taking too optimistic a view aren't all that severe...
except, of course, if you're wasting transmissions for "liveness"
checks, or needlesssly sending some latter-day analogue of the old
NCP RST, or being charged by some comm subnet for the apparently open
connection, or.... Oops, guess I still feel you oughta be prudent.

Well, that's probably more than enough on the subtopic for/from me, so:

cheers, map

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