Re: Live Byte Ranges

Craig Pratt <craig@ecaspia.com> Mon, 28 November 2016 21:11 UTC

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References: <CAOdDvNrrLfh0yV4UdBN_HpHNfD024Kufibe3D4ZB1N-SqYVt4g@mail.gmail.com> <35074.1480362772@critter.freebsd.dk>
From: Craig Pratt <craig@ecaspia.com>
Organization: Caspia Consulting
Message-ID: <22408585-750a-778e-069b-57f624549604@ecaspia.com>
Date: Mon, 28 Nov 2016 13:06:13 -0800
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Subject: Re: Live Byte Ranges
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Thanks much for the feedback.

Reply in-line.

cp

On 11/28/16 11:52 AM, Poul-Henning Kamp wrote:
--------
In message <CAOdDvNrrLfh0yV4UdBN_HpHNfD024Kufibe3D4ZB1N-SqYVt4g@mail.gmail.com>
, Patrick McManus writes:

To summarize briefly - this addresses the problem of addressing byte ranges
of dynamic (growing) content. A number of solutions have seen false starts
in this space previously, but this one has a shot at being compatible with
existing infrastructure.
Varnish will almost certainly implement whatever comes out of this.
I should add that I'm going to submit a patch to Rygel (the Gnome media streaming package) to support this draft as well.

Notes from our mumblings in the project:

The "Very Large Value" solution it is brittle in more ways than is
desirable, but try as we may, we don't see any simpler/better ways
of doing it without negotiation/hints.
Agreed. I wish there was a better way. Maybe the rust can be cleaned off of Range Units by filing some bugs against implementations that are making assumptions about Range Units. Even if it's not used/helpful here, it might open the door for some other applications.

We suggest to either put a "Quite Large" lower limit on "Very Large
Value", or better yet:  Make it a magic value large enough to not
be a problem relative to actual Range requests.  If we keep with
the 9's motif from the draft, we suggest 999999999999999999 which
doesn't needlessly provoke 64-bit sign issues.
I thought about the magic value approach. It's certainly more deterministic to use a Quite Large Magic Value (QLMV?) - and easier to specify and code. And it's entertaining to think up magic values (e.g. 2^63 - 42) (but agreed that all 9s does a better job of jumping out to us humans). I just couldn't suppress my engineering gag reflex at the whole concept. This reflex has some adjustment, but I'm presuming it's a common reaction.

I also didn't like the idea of forcing a limit. But 2^63 is a crazy-large number. At 50Mb/s, the representation could cover over 46000 years, according to my quick math (with 999999999999999999 covering a mere 5073 years). And there's nothing preventing the definition/addition of a VLMV now or later. I just can't help but wonder if a Registry of Magic Values would then be in order (there's that gag reflex again).

Anyway, I'm good either way so long as there's general consensus. I tried to cover the issue of values larger than 2^63 in the Security Considerations section. Perhaps a "should" or recommended QLMV/VLMVs would be a way to go? Other thoughts/opinions appreciated here.


Typo on page 3: "accessable"

Thanks. It'll be corrected in the next version. (Somehow "accessable" is in my mac's spelling dictionary)

cp

--

craig pratt

Caspia Consulting

craig@ecaspia.com

503.746.8008