[e2e] Protocols breaking the end-to-end argument
jnc at mercury.lcs.mit.edu
Sat Oct 24 11:00:15 PDT 2009
> From: Richard Bennett <richard at bennett.com>
> The best discussion I've seen of function placement in a datagram
> network to this day is found in Louis Pouzin's mongraph on the CYCLADES
> network, _Cyclades Computer Network: Towards Layered Network
> Applications_, Elsevier Science Ltd (September 1982).
I'm not sure I'm totally on board with that "best" attribute, but the work of
Pouzin et al was an _extremely_ important step in the evolution of networking,
and often does't get the credit it deserves (e.g. one of the papers I read in
preparing to respond to this email didn't mention it, in reviewing the
philosophical development of the architecture of TCP/IP).
> Tim Moors' "A Critical Review of End-to-End Arguments in System
> Design", http://www.ee.unsw.edu.au/~timm/pubs/02icc/published.pdf.
A good and interesting paper; thanks for bring it to my attention. I do think
it goes off the beam in a couple of places, though.
For one, NATs became widespread mostly a result of flaws in the original
engineering (too small an address space) and architecture (too few namespaces,
leading to difficulty in supporting things like provider independence). NATs
are not inherently desirable, and would not, I think, have
evolved/proliferated had TCP/IP avoided those (in hindsight, now obvious)
For another, the current routing architecture has been driven much more by
factors such as technical hysteresis (both personnel familiarity with the
existing distributed computation model, as well as 'if it isn't broken, don't
fix it') and 'alligator' syndrome (as in 'when you're up to your
you-know-what in alligators [growing the network, in this case], you don't go
looking for more not-immediately-important fights').
Still, those are nits in the overall sweep of the paper.
> Moors shows that the Saltzer, Reed, and Clark argument for end-to-end
> placement is both circular and inconsistent with the FTP example that
> is supposed to demonstrate it.
I didn't see that at all.
> One of the more interesting unresolved questions about "End-to-End
> Args" is why it was written in the first place. Some people see it as a
> salvo in the ISO protocol wars, others as an attack in BBN's ARPANET,
> some as an attempt to criss the divide between engineering and policy
I don't know whether to be amused or outraged by this nonsense.
I will settle for observing that you probably haven't interacted much with
Jerry - because had you done so, it would have been utterly obvious to you
that overwhelmingly his most important motivation in writing the paper was
his deep commitment to improving the art of system architecture.
Dave Reed is here to defend himself, and as to Dave Clark, I would be prepared
to bet pretty much any stakes that he'd be in the front rank in acclaiming the
ARPANet as a huge step forward in information networking.
The reference to the "ISO protocol wars" is completely mystifying, as the
architecture of the ISO stack (at least, the CLNP/TP4 flavour, which was the
subset which gave TCP/IP the best 'run for their money') is basically
identical to that of TCP/IP (modulo disagreements on certain arcane points,
such as exactly what kind of abstract entities the names at the various levels
refer to - a subject wholly unrelated to the end-end debate).
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