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Re: SPDY Review

From: Martin Nilsson <nilsson@opera.com>
Date: Sat, 09 Jun 2012 00:30:09 +0200
To: "Mike Belshe" <mike@belshe.com>
Cc: "Roberto Peon" <grmocg@gmail.com>, ietf-http-wg@w3.org
Message-ID: <op.wflvgjmbiw9drz@manganese.bredbandsbolaget.se>
On Fri, 08 Jun 2012 21:10:59 +0200, Mike Belshe <mike@belshe.com> wrote:

>>>
>> I'm using the same data as the http://www.eecis.udel.edu/~**
>> amer/PEL/poc/pdf/SPDY-Fan.pdf<http://www.eecis.udel.edu/~amer/PEL/poc/pdf/SPDY-Fan.pdf>and  
>> when using the evaluation set they use I actually get somewhat better
>> compression values (probably due to better header normalization).
>
>
> The point of SPDY header compression is to use stateful compression.  If
> you only compress one chunk of headers, you'll get modest savings -  
> 30-50%.
>  but on the second set, you get like 95% :-)  For SPDY sessions in steady
> state, the typical size of a request is 50-60 bytes.  Almost everything,
> including the cookies, compresses out.
>

Yes, that is quite clear from the specification, and I noted "deflate with  
persistent context is a good approach" in the original text. The context  
here is about using a deflate dictionary, and then the subsequent requests  
compress almost equally well without dictionary. This is natural given how  
LZ77 works and the repetitive nature of HTTP headers. So if you are only  
making single requests on every SPDY connection, the dictionary gives you  
a 15-25% boost on the header compression. If you are making multiple  
requests you will however very quickly see the benefit over normal deflate  
disappear.

/Martin Nilsson

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Received on Friday, 8 June 2012 22:30:33 GMT

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