Re: Internet Uselessness


Michael Padlipsky (PADLIPSKY@A.ISI.EDU)
22 Jul 1987 10:28:45 EDT


H. Craig--

Just to show the unbelievers that there are some windmills even I
won't bother to lance, I'll merely answer your final rhetorical
question ("The Commercial/PTT networks can do it, why can't we?"):
As I understand the "it" John and Andy and I were talking about,
it's dealing with presented loads greater than a system was designed
to deal with; if you really think the PTTs know how to get five pounds
of bits in a two-pound sack, I hope you'll share your knowledge with us
all. In other words, if it's physically impossible, even we can't
do it--but neither can They....

It would be too Zen to get into the subtleties of the flavor of
pie in the sky vs. the taste of bread in the mouth, but I would
feel myself remiss if I didn't mention that I've been aware of
pricing as a resource-demand regulator since my CTSS days, where
Corby told me it was already known for years to the phone company;
so I'd suggest that if the PTTs aren't groaning under their presented
loads (and for all I know they are but just don't talk about it in
public) it's because they have extra-protocol ways of limiting
the loads. And, for that matter, if 40-byte headers bother you,
how about you be the one who finally does the exercise of totalling
up the sizes of the Network (actual), Network ("connectionless" [a/k/a
IP], Transport, Session, Presentation, Application, and Management
(times 5 or 6) "PDUs": after all, another good way of keeping the
loads down is to make things so barococo that nobody can fabricate
a load to present, right?

   pro forma cheers, map

P.S. Andy's reply to me, my reply to it, and his reply to my reply should
cast some light on the flavor of virtual circuits we were talking about
at the subnet processor to subnet processor level; sorry, I don't think
you can rightly infer that IMPs/PSNs "are" X.25 node to node. Indeed,
the fundamental problem of the Internet in one sense is that there is
not and cannot be A node to node protocol at the subnet level, since
the subnet level is by definition hetereogenous. Andy is adressing
the/a backbone subnet, which contrary to its original design parameters
is now dealing with a multiplicity of (to it) ancillary subnets; X.25
on the other limb is offering some (by spec) no more than 56.2 kb/s
"trunks", take 'em or leave 'em. It's like comparing apples to
orange pits (or pips, if John Laws is still tuned in) to imagine that
Arpanet and "the PTTs" are interchangeable. Try hooking say a 10-meg
Ethernet up to an X.25 PSN: you've either got a 56.2 bottleneck
or you're building some sort of milking machine and paying for
multiple X.25 ports even if your Hosts are "doing" X.25 as their
end-to-end/"Transport" protocol, but if the Hosts are doing the
ISO Stack, you've the same Gateway bashing problems as in the
Internet--with, almost certainly, a far less flexible/responsive
"backbone"....
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