Re: Issue with "bytes" Range Unit and live streaming

Reply in-line.

cp

On 5/11/16 6:16 PM, Adrien de Croy wrote:
>
> unless we allow Content-Length to also use the new unit (which I'd be 
> dead against), I'd suggest we steer clear of minting any new range units.
>
[cp] I don't see how a Range Unit would apply to Content-Length.

Regardless of how a range is requested, the server is always 
transferring bytes in the response body - whether indicated by 
Content-Length, chunks, or whatever. The Content-Range response header 
just lets the server indicate the returned range associated with the 
response body *in terms of the indicated range unit* and *in the domain 
of the representation*.

e.g. If a Range Unit called "blobs" is used, and a request is made with 
"Range: blobs=5-11", the response could have header "Content-Range: 
blobs=5-11/50" indicating that 7 blobs are being returned (out of 50) in 
the response body and a "Content-Length: 123456" could also be supplied 
designating that the response body (associated with blobs 5-11) is 
123456 bytes.

Am I missing something?

> All the proposed use cases for new range units that I've seen are 
> application specific, and could arguably better be dealt with using 
> another header.
>
> Adrien
[cp] Doesn't the fact that there's a Range Unit Registry mean that Range 
Units can be added that are application-specific - assuming there's 
sufficient demand? It's just a different mechanism than adding custom 
headers, IMHO - with well-defined semantics.

>
>
> ------ Original Message ------
> From: "Mark Nottingham" <mnot@mnot.net>
> To: "Darshak Thakore" <d.thakore@cablelabs.com>
> Cc: "ietf-http-wg@w3.org" <ietf-http-wg@w3.org>
> Sent: 12/05/2016 12:59:25 p.m.
> Subject: Re: Issue with "bytes" Range Unit and live streaming
>
>> Hi Darshak,
>>
>> I don't think that's where we're at. Based on the discussion so far, 
>> it seems like there are two possible paths forward:
>>
>> 1. Changing the 'bytes' range-unit to allow this use case
>> 2. Minting a new range-unit
>>
>> As discussed, both have downsides. What we need is data about how 
>> current implementations -- especially caching intermediaries -- 
>> behave when faced with a) 'bytes' used in the desired way, and b) a 
>> new range-unit.
>>
>> Cheers,
>>
>>
>>>  On 11 May 2016, at 5:57 AM, Darshak Thakore 
>>> <d.thakore@cablelabs.com> wrote:
>>>
>>>  Hi all,
>>>
>>>  Based on feedback on this thread, it seems like the need for being 
>>> able to send an open ended (read as unknown-last-byte-pos) Range 
>>> response has been discussed a couple of times (with different use 
>>> cases). Also there seems to be somewhat general agreement that the 
>>> Content-Range ABNF in RFC 7233 is deficient in providing this. The 
>>> initial argument has been, “is there a compelling enough need” and i 
>>> think with different use cases popping up (log files, media 
>>> streaming, gzip… others ??) there seems to be some value in defining 
>>> a non-application specific Range unit that plugs this gap. Clearly 
>>> fixing RFC 7233 is invasive and will result in thing breaking in 
>>> unknown ways so that’s a no-go. With that, we can:
>>>   • Ensure that the scope of this work item is narrow and restricted 
>>> only to fixing the gap in RFC 7233
>>>   • Define a new range unit (anything with “bytes” in it seems like 
>>> a bad idea, so maybe call it “live-octets”, “blive”, “b-add" - 
>>> suggestions welcome….)
>>>   • Decide if there is enough interest/reason to do this as a WG item
>>>  Any objects/suggestions to any of the above ?
>>>
>>>  Regards,
>>>  Darshak
>>>
>>>
>>>  From: "K.Morgan@iaea.org" <K.Morgan@iaea.org>
>>>  Date: Thursday, April 21, 2016 at 4:25 AM
>>>  To: 'Craig Pratt' <craig@ecaspia.com>, "fielding@gbiv.com" 
>>> <fielding@gbiv.com>
>>>  Cc: "ietf-http-wg@w3.org" <ietf-http-wg@w3.org>
>>>  Subject: RE: Issue with "bytes" Range Unit and live streaming
>>>  Resent-From: <ietf-http-wg@w3.org>
>>>  Resent-Date: Thursday, April 21, 2016 at 4:25 AM
>>>
>>>  On Thursday,21 April 2016 05:18 craig@ecaspia.com wrote:
>>>  >
>>>  > Re: Representation caching
>>>  >
>>>  > Whether a representation is considered cacheable in this use case 
>>> is at
>>>  > the discretion of the origin server and specific to the use
>>>  > case/application - as it should be (imho). There's no *necessity* in
>>>  > having a periodically-appended resource marked non-cachable, 
>>> correct? If
>>>  > the resource mutates, it's not cacheable. If it's just being 
>>> appended
>>>  > to, it is cacheable. And if an appended resource stops being 
>>> appended
>>>  > to, it doesn't invalidate the cached representation.
>>>  >
>>>
>>>  I couldn't agree more. However, it seemed the prevailing sentiment 
>>> when we tried to resolve the related issue of ranges before content 
>>> codings, with a new bbcc unit (bytes-before-content-coding), was 
>>> that the use cases for append-only growth represent an insignificant 
>>> portion of HTTP traffic. “We live by app-specific protocols to 
>>> handle these cases. What is so special ... that it must be addressed 
>>> by http (in a very ugly way)?” [1]
>>>
>>>  [1] 
>>> https://lists.w3.org/Archives/Public/ietf-http-wg/2014AprJun/1383.html
>>>
>>>
>>>
>>>  This email message is intended only for the use of the named 
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>>
>> -- 
>> Mark Nottingham   https://www.mnot.net/
>>
>>
>
>


-- 

craig pratt

Caspia Consulting

craig@ecaspia.com

503.746.8008

Received on Thursday, 12 May 2016 02:02:11 UTC