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RE: #466 segment compression

From: <K.Morgan@iaea.org>
Date: Thu, 1 May 2014 22:42:28 +0000
To: <grmocg@gmail.com>
CC: <matthew@kerwin.net.au>, <ietf-http-wg@w3.org>, <martin.thomson@gmail.com>
Message-ID: <0356EBBE092D394F9291DA01E8D28EC201129877D8@sem001pd.sg.iaea.org>
On 02 May 2014 00:01, I wrote:
> On 29 April 2014 21:57, grmocg@gmail.com wrote:
>> If compression is per-segment as opposed to per-frame
>>    AND we wish to restrict the amount of state the server must keep around
>>    AND the sender wishes to have all the data in the segment compressed
>>   THEN then the segment being compressed must be sent in its entirety in a contiguous series of frames with > no muxing of other streams in the middle.
> The exact same problem exists for dynamic compression with C-E.  How are you going to solve that?

Sorry to reply to my own e-mail, but I really think this does apply to dynamic C-E compression and is a DoS vector.

Suppose a client sends N request for various entities that are dynamically compressed, where N=MAX_CONCURRENT_STREAMS and suggests an equal priority for each. If the server gives equal priority to serving each stream, it will have N outsanding compression contexts until all requests are serviced. By contrast, in HTTP/1.1, even with pipelining, a single client on a single connection would only ever require one compression context on the server to service its requests.

This is an argument in favor of using frame-by-frame compression for dynamic compression since frame-by-frame compression _can_ be implemented with only one outstanding compression context at any given time.  It's also an argument for mandating client *support* for frame-by-frame gzip (i.e. non-optional) because it always gives servers a way out from this DoS vector.

Has anybody implemented a native HTTP/2 server with dynamic compression support that can speak to this problem?
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Received on Thursday, 1 May 2014 22:43:07 UTC

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