Re: Internet Uselessness


PADLIPSKY@A.ISI.EDU
17 Jul 1987 14:44:03 EDT


[The following got to John, but not to the List, thanks to the vagaries
of trying to Answer on his foreign To and CC fields:]

John--
   As I understand your msg, "the PTT way" amounts to Overcharge So That
You Can Overengineer. The Internet way, however, doesn't have to be
Undercharge And You Must Underengineer. How about, instead, Undercharge
And You'd Better Engineer A Lot More Cleverly? For example, I recall
that in the Multics NCP [sic] I had a privileged primitive that let me
ignore packets from a Host on a blacklist at interrupt time (which was
actually used once, during the infamous Network Horror Story Number 5):
Why not use a similar trick in Gateways? Say, on a 30-second cycle (or
whatever time value seems appropriate) check the per-Host packet counters
(added for the purpose) and put any Host that's exceeded a threshold
count on the List for the next cycle. A tad arbitrary, perhaps, but
much easier to implement than trying to spot and throttle sf-lovers file
transfers/SMTPs. (The threshold should probably be a fraction of
total packets for the period rather than a set number, so that periods
of relative inactivity for other Hosts behind the Gateway can be
catered to--but this is just a "frinstance," not a spec, so no matter.)
   The example isn't necessarily to be taken literally, of course; it's
just meant to suggest a principle to the effect that you can combat
resource hogging creatively without violating protocol (since Gateways
are explicitly allowed to drop packets on the floor) on the one hand
yet without having to "go commercial" on the other hand.
   Actually, I've long suspected that the real problem with the
Internet Way is that we draw so heavily on Academe that clever
engineering is somehow suspect because it's not Computer Sciencey
enough somehow. I mean, granted we couldn't have afforded to throw
as much hardware as we might have liked at Gateways from the outset,
but it still seems to me that all the pious queuing-theoretic stuff
about one buffer is enough and even infinite buffers aren't enough
and the like has clouded the issue so much that we still (unless
the relevant Task Force is about to step in) haven't come up with
a rough and ready congestion control approach because we "know"
it wouldn't be "optimal". Well, as I've said before Optimality
Differs According To Context.
   cheers, map
P.S. As I recall, the X.25 spec certainly _implies_ that there won't
be any dynamic routing, both in one of the error returns and, for that
matter, in the whole "virtual circuit" premise (since destination addrs
aren't carried in ordinary packets), but, yes, They could do it right
despite all that if They had/wanted to. Does anybody know of an
implementations that do do it right, though? (And even if there are some,
so what? We could have some segments of the Internet which used
Multics Gateways if we wanted/had to. Some old saw about weakest links
still seems to apply....)
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