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Re: HTTP router point-of-view concerns

From: Amos Jeffries <squid3@treenet.co.nz>
Date: Fri, 12 Jul 2013 20:26:19 +1200
Message-ID: <51DFBDAB.9010505@treenet.co.nz>
To: ietf-http-wg@w3.org
On 12/07/2013 7:35 a.m., Roberto Peon wrote:
> I think it is perfectly reasonable for an intermediary to set the 
> compression size to zero if it wishes.
> Market forces will (in the long-term) pick the correct strategy for 
> this-- assuming the compression is effective at reducing latency, and 
> that people care about latency reductions, then eventually 
> intermediaries might evolve to use it.
> If it is ineffective at reducing latency, or if reduced latency is not 
> actually desirable, then intermediaries would not use it.
> The DoS vector you're talking about is not a DoS vector if the 
> intermediary resets all streams before the change-of-state-size comes 
> into effect.

If you means RST_STREAM on all the initial streams which use a larger 
compression size then what you are doing is adding an RTT penalty to all 
those requests over and beyond what HTTP/1 suffers from already on a 
normal transaction. This is not a useful way forward (wastes packets, 
RTT and stream IDs) and resolving it is to make decompression with the 
default state size mandatory for all recipients. Which brings us full 
circle on the problem of having a default >0 in the dynamic part of the 
state tables.

> When the state size is 0, one should be able to use some kinds of 
> 'indexed' representations, so long as those representations refer only 
> to items in the static tables. Why do you believe that this would use 
> more or less CPU? (It should use less CPU and less memory...)

I did not mention CPU. Only the bandwidth amplification effects that 
agents disabling compression would incur and need to consider carefully.

Personally I would like to see a 127 entry mandatory static table in the 
spec itself and tied to the "2.0" version with a 127 entry optional 
dynamic table indicated by the high-end bit of the byte code. With a 
capacity byte size for dynamic table sent each way and senders forbidden 
to add new entries to the dynamic table until they hold the value from 
both ends of the connection. Agreed value being the minimum of both ends 

Received on Friday, 12 July 2013 08:26:49 UTC

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