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Re: multipart/byteranges

From: Jeffrey Mogul <mogul@pa.dec.com>
Date: Mon, 04 Aug 97 15:47:42 MDT
Message-Id: <9708042247.AA04857@acetes.pa.dec.com>
To: http-wg%cuckoo.hpl.hp.com@hplb.hpl.hp.com
    We don't handle multipart/byteranges. We NEVER ask for more than
    one range. Having to put in a parser for multipart/byteranges into
    the level of the stack which handles generic HTTP (in our case that
    would be WinInet) would be extremely difficult. That level in the
    stack doesn't do the sort of heavyweight parsing needed for
    multipart. It is really designed for quick and dirty parsing on the
    level of "Identify headers and body, return."

Aha, I misunderstood your question.  Certainly if a client only
makes requests for single contiguous ranges, it shouldn't have
to be able to parse multipart/byteranges responses.

I misunderstood your question because I thought you were talking
about a case where the server might coaelesce two requested
(and overlapping) ranges into a one-part "multipart" response.

    Given that others are in the same situation it would seem
    reasonable to put in language requiring that multipart/byteranges
    not be used if a single range is being returned.
    
The language is already there, although in a different part of the
spec (quoting from RFC2068, not draft -08, which I don't have handy):

   4.4 Message Length:

   When a message-body is included with a message, the length of that
   body is determined by one of the following (in order of precedence):

   [...]

   4. If the message uses the media type "multipart/byteranges", which is
     self-delimiting, then that defines the length. This media type MUST
     NOT be used unless the sender knows that the recipient can parse it;
     the presence in a request of a Range header with multiple byte-range
     specifiers implies that the client can parse multipart/byteranges
     responses.

One could argue that this "MUST" ought to be more obvious (although
I found it quickly using a text-search on "multipart/byteranges").
But I think this is exactly what you want, right?

I.e., what matters to you is NOT that a multipart/byteranges have
more than one subrange (since one could, in principle, break up
a single range into multiple contiguous subranges), but that the
server never send any multipart/byteranges responses to a client
that isn't prepared to parse them.  Right?

-Jeff
Received on Monday, 4 August 1997 15:51:42 EDT

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