[e2e] UDP checksum field?

Cannara cannara at attglobal.net
Wed Apr 6 20:20:10 PDT 2005

Well, long Erudite reponses are always welcome Ethan, but rather than
Beccaria, even I, as an Italian American, actually prefer Mao: "All political
power stems from the barrel of a gun".  :]


Ethan Blanton wrote:
> Cannara spake unto us the following wisdom:
> > Of course, David, but the opposite is: no checksum = no chance of
> > correctness.  And, the way NAT and other boxes have been intended and
> > deployed, many people consider them as "ends", making the mythical End-End
> > Principle even more of a fantasy.
> I'm not sure exactly what you're trying to say here (I seldom am), but I
> think it misses a very important point.  There  are  in  fact  a  _very_
> large  number  of applictions which obey the end-to-end principle exten-
> sively.  Take as an example class of such applications all  SSL  or  TLS
> streams over TCP.
> If  [heh]  you  have a particular axe to grind, you can probably come up
> with some little semantic corner where this is not end-to-end  in  every
> respect, but it will be just that -- a semantic little corner.  SSL over
> TCP performs end-to-end flow  control,  end-to-end  congestion  control,
> weak end-to-end integrity checking at the transport layer, and extremely
> robust end-to-end integrity checking (possibly as  well  as  authentica-
> tion)  at the application layer.  Note that, in this example, each layer
> of the stack provides the largest reasonable set of  guarantees  it  can
> provide,  and  the  ultimate  "end-to-end"  integrity and authentication
> checks are performed at the _true_ ends of the connection -- the  appli-
> cation.
> I  realize  this  message is probably futile, but I hope it will end the
> bickering over semantics in this particular  thread,  and  provide  some
> food  for thought for future such threads.  No, the end-to-end principle
> isn't practiced everywhere, but it is far from a "fantasy". And yes, I'm
> sure  Ma  Bell  provided perfect end-to-end service via POTS in 1908 and
> the Internet is so far behind we might as well not even  bother  talking
> about  it,  no need to tell me that.  Since I use the Internet every day
> (and, miraculously, it works), I'll leave  mailing-list  theories  about
> how it can't possibly work on the shelf for now.
> Ethan
> --
> The laws that forbid the carrying of arms are laws [that have no remedy
> for evils].  They disarm only those who are neither inclined nor
> determined to commit crimes.
>                 -- Cesare Beccaria, "On Crimes and Punishments", 1764
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