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Re: Use cases and requirements for Media Fragments: Chapter 8

From: RaphaŽl Troncy <Raphael.Troncy@cwi.nl>
Date: Tue, 07 Apr 2009 22:36:21 +0200
Message-ID: <49DBB945.3080201@cwi.nl>
To: Conrad Parker <conrad@metadecks.org>
CC: Yves Lafon <ylafon@w3.org>, Media Fragment <public-media-fragment@w3.org>
Dear Conrad,

> I've been thinking about generalizing this mechanism a bit recently to
> allow caching of non-header data. Here's some notes towards that:
> http://blog.kfish.org/2009/04/proposal-for-generalizing-byte-range.html

Great post! Thanks!
However, I'm a bit puzzled with your proposal. From my understanding, 
the 4-ways handshake is meant to resolve a range request, e.g. in 
seconds into a byte range request. As Yves pointed out, we need a 
resolver that can do that, providing what ultimately the codec format 
allows to do.
On the other hand, it seems to me that your proposal aims at solving the 
problem of answering a complex request with multiple by ranges, while I 
do not understand what the UA needs to do with the set of bytes it will 
receive to have a playable resource.
Therefore, could you explain me what the 'Range-Referral' new header is 
meant to do?

> As for terminology, I really don't think the term "handshake" is
> appropriate; especially when all that's really happening is that the
> data retrieval is getting split across multiple HTTP requests.
> Handshake seems to imply that just negotiation is going on, and that
> this is delaying the actual data retrieval -- which isn't the case
> here.

I agree that the term 'handshake' is not necessarily adequate, though I 
cannot find a better one :-( In the Western world, the term handshake 
sometimes suggests that the negotiation is over. So, in our case, we 
could speak off *a* handshake when all the rountrips have been 
successfully made. Can you suggest a better term ?

In the meanwhile, I suggest to add the following editorial note in the 
WD in the section 8.0:

"In the following, we use the terms <emph>two-ways handshake</emph> when 
there is one roundtrip and <emph>four-ways handshake</emph> when there 
is two roundtrips between the UA and the server. We acknowledge that 
these terms are not necessarily adequate and we seek suggestions for 
having better terms for naming these processes."

Can you live with that?


RaphaŽl Troncy
CWI (Centre for Mathematics and Computer Science),
Science Park 123, 1098 XG Amsterdam, The Netherlands
e-mail: raphael.troncy@cwi.nl & raphael.troncy@gmail.com
Tel: +31 (0)20 - 592 4093
Fax: +31 (0)20 - 592 4312
Web: http://www.cwi.nl/~troncy/
Received on Tuesday, 7 April 2009 20:37:15 UTC

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