[e2e] patents on routing algorithms

Jon Crowcroft Jon.Crowcroft at cl.cam.ac.uk
Fri Jan 4 05:51:12 PST 2008

why do you think a loose coupled system cannot be described
mathematically? clearly I can describe the code at each end of a
protocol, and the channel, and at least derive theorems about how
these combine. just because i dont over determine thigns doesn't mean
that there isnt a precise mathematical description - it just means
that there are non deterministic (external) events....thats been
smething that process algebras have addressed since CCS, CSP, Lotos
etc etc...even though those systems were somewhat unwieldy

many processor designs today are specified - but a ot of asynch
circuit design has to be underdetermined....that doesnt mean it isnt
amenable to math (code/algorithmic) description.

you're starting to sound like Richard Dawkin's who seems to think that
human consciousness is not amanable to emulation by machine because
of quantum mechaninics....an even great heresy

description doesn't mean 100% prediction...:)

In missive <477E37CF.5010707 at reed.com>, "David P. Reed" typed:

 >>Jon Crowcroft wrote:
 >>> it is a goal of much recent work (see Sewell et al in sigcomm 05
 >>> "Rigorous specification and conformance testing techniques for network protocols,
 >>> as applied to TCP, UDP, and sockets"
 >>> and various papers
 >>> by Griffin and Sobrinho on Metarouting) 
 >>> to render protocols merely 
 >>> algorithmic specifications that are fed into engines that run them
 >>> shame on us as computer scientists that
 >>> we dont use such techniques on a daily basis for
 >>> well-found engineering instead of the handwaving that passes
 >>> for communications work still in the 21st century
 >>> it is a technical AND ethical goal to make it so
 >>> and should be a duty on all of us to get the law to recognize it
 >>That's a plausible point of view.   I heartily disagree, however.  In 
 >>1974 or so, our research group (Saltzer, Clark, Reed, Liskov, Svobodova, 
 >>as I recall) decided that a *crucial* aspect of distributed systems was 
 >>that they exhibited "autonomy", which implies a serious notion of loose 
 >>coupling, flexibility, revisability, etc.  That set of attributes are 
 >>crucial, leaving them out for the sake of formal methods is just another 
 >>Procrustean bed, where they are the Feet.
 >>*Protocols* are techniques for achieving communications in the face of 
 >>uncertainty about who is on the other side of the network.  Not just an 
 >>unreliable network in the middle, but an uncertainty in a very 
 >>fundamental sense about what is on the other side.
 >>In "distributed systems" that must function in the real world, a core 
 >>and *essential* concept is that one must specify parts of the system to 
 >>To someone who speaks English as a protocol, this is obvious.   I can 
 >>try to convince you, for example, by the words above that I am right.   
 >>And I am using English correctly, and this can be verified.  But it has 
 >>nothing to do whatsoever with being able to prove that you *will* agree 
 >>with me at the end of the conversation.  Maybe it will take more 
conversations, maybe not.
 >>But a protocol is not an algorithm executed by a complete set of formal 
 >>machines, though some protocols (a small subset might be in that 
 >>category).  That is a sad, little boring and utlimately trivial subset 
 >>of the "protocols" of the world.   Maybe it makes small-minded 
 >>mathematicians happy because they can close off a "formal system" and 
 >>prove theorems, as if proving theorems is the desired endpoint of system 
 >>design.    But the ability to prove theorems is not the test of a 
 >>*useful* protocol set - neither of engineering value, nor of human 
 >>value.   The ability to communicate (which cannot be formalized in any 
 >>way I know) is the correct test.   The Internet is one example of a 
 >>system that succeeds in communicating, and there really was NOT a need 
 >>to define a formal specification of a collection of machines to achieve 
 >>that result.



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