Re: [Int-area] Warren Kumari's Yes on draft-ietf-intarea-frag-fragile-15: (with COMMENT)

[Geoff Huston <[e-mail]>]

> 
> 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