> 
> Geoff,
> 
> The broad measurements are almost always a limited viewpoint taken at point 
> in time.

I was referring to Internet measurements using the Internet. The conversation 
was (I thought) about the prospects for ever cleaning up Internet middleware on 
the Internet. The context of the conversation was the context of applic ations 
behaviour __on the Internet__.

Of course there are many other contexts. Decnet Phase III may be doing just 
fine in some of them and I’m sure there are many protocols and many variants 
are being used in many contexts. If we were ever to attempt to interpret RFCs 
as containing some eternal and universally applicable truth about IP as used in 
every possible context in every possible way then I for one am cheerfully 
prepared to give up at once, as I believe that this is a Sysyphalian task.

> As discussed several times in regards to fragmentation, it's not broken for 
> everyone all the time. It is being used productively in some contexts.


Of course - but the advice is not about what may work on Thursdays on a sunny 
day on a downhill slope. Its more about lowest common denominator set of 
pragmatic considerations that start with the premise that if you have no idea 
where or why your application may be used, then what would be a sensible set of 
design choices that would maximise its applicability and robustness, 
irrespective of the day of the week, the inclination of the bits and the 
outside temperature. 

Like I said its about interpretation of these IETF documents. If you believe 
that RFCs are like some Networking Canon of immutable laws of moving bits then 
yes, many things work in many situations and its just not possible to say 
outright “this will not work in every case!” about almost everything. But in my 
mind this document is not striving for any such lofty goal. It’s pointing out 
that IP fragmentation is extremely fragile, and in IPv6 more so. As an app 
designer and if you are desirous of maximising robustness and applicability for 
you application then you should steer clear of fragmentation, if you can.

regards,

  Geoff

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