Re: ID for Immutable

Alex Rousskov <rousskov@measurement-factory.com> Fri, 28 October 2016 15:34 UTC

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References: <CAOdDvNqam930_0eA1p3yHW+xDdOm0AAMKvVKe6xwNwm1itpRpQ@mail.gmail.com> <20161028144407.48EFF162D1@welho-filter4.welho.com>
From: Alex Rousskov <rousskov@measurement-factory.com>
Cc: Kari Hurtta <hurtta-ietf@elmme-mailer.org>
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Date: Fri, 28 Oct 2016 09:23:54 -0600
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Subject: Re: ID for Immutable
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On 10/28/2016 08:44 AM, Kari Hurtta wrote:
> If server can't calculate hash-function over resource,
> is is really static non-caching resource?

There is sometimes a big difference between the _ability_ to calculate a
hash and the _expense_ of doing so. AFAICT, immutable responses may
still be dynamically generated (or otherwise costly to produce) on the
origin server.

For example, loading, encoding, and hashing a 2-hour video of the 1948
Olympics opening ceremony could be rather expensive, but will produce
the same immutable result [until the server has to inject a fresh set of
advertisements sometime tomorrow].

Alex.