Re: [hybi] With deflate-stream, Close frame doesn't work as an end of data marker

[Greg Wilkins <[e-mail]>]

I'm +1 for compression within the frame.

If we compress the framing, then intermediaries will have to
decompress in order to see framing and to know when to forward etc.
It also has significant debug issues as it makes it much harder to
decode a partial frame capture.

I understand the argument that compression will not be as good, but I
think some compromise is necessary.

To look at the analogy of HTTP, compression does not change HTTP
framing and intermediaries do not need to be updated to deal with any
new compression algorithms that may be deployed.

regards



On 25 February 2011 16:19,  <[e-mail]> wrote:
>
> Hi,
>
> If we could apply deflate-stream only to payload, that would solve
> the problem. I was looking for reasons why entire stream has to be
> compressed, and found only one here:
>
> http://www.ietf.org/mail-archive/web/hybi/current/msg04117.html
>
> From layering aspects, I would prefer any compression taking place
> on top of framing layer from the other way around:
>
>    +-------------+
>    | compression |
>    +-------------+
>    +-------------+
>    | WS framing  |
>    +-------------+
>    +-------------+
>    |     TCP     |
>    +-------------+
>
> where, current draft -05 sugggests:
>
>    +-------------+
>    | WS framing  |
>    +-------------+
>    +-------------+
>    | compression |
>    +-------------+
>    +-------------+
>    |     TCP     |
>    +-------------+
>
> Justifications for the former layering would be:
>
> o  Framing is necessary because of the underlying transport
>    layer is in fact 'streaming', or TCP. (TCP and WS-framing
>    are more tightly coupled)
> o  WS-layer needs to buffer entire message (passed by app/JS)
>    anyway.
> o  Text and binary do not interleave fragments, hence there
>    needs only one context for compression / decompression in
>    memory.
> o  Overhead (frame headers and control frames) are much smaller
>    than payload of text/binary frames and negligible as to
>    compression ratio.
> o  Close frame appears at the end of stream with no traling
>    bytes. (Can remove requirement for TCP graceful shutdown).
>
> Please let me know if I am missing something...
>
> Best.
> - Yutaka
>
>
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