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Re: Review: http://www.ietf.org/id/draft-mbelshe-httpbis-spdy-00.txt

From: Adrien de Croy <adrien@qbik.com>
Date: Thu, 01 Mar 2012 17:00:16 +1300
Message-ID: <4F4EF450.1040406@qbik.com>
To: Brian Pane <brianp@brianp.net>
CC: ietf-http-wg@w3.org

need to add a few more RTTs for TLS.

Adrien


On 1/03/2012 4:52 p.m., Brian Pane wrote:
> On Wed, Feb 29, 2012 at 5:40 PM, Amos Jeffries<squid3@treenet.co.nz>  wrote:
>> On 01.03.2012 13:39, Mike Belshe wrote:
>>> If the protocol is allowed to be slower than HTTP/1.1, then you could do
>>> this.  But, a lot of server operators that care about performance aren't
>>> going to want to take that hit.
>>
>> That is what bothers me about all the arguments against Upgrade: based on
>> extra RTT and lag.
>>
>>   today: HTTP/1.1 request + HTTP/1.1 response   == 1 RTT
>>
>> versus
>>
>>   tomorrow: HTTP/1.1 request /w Upgrade header + XYZ response /w 200 status
>> prefix   == 1 RTT
> I use a different comparison:
>
> HTTP/1.1 today:
>      TCP handshake: 1 RTT
>      HTTP/1.1 request for resource 1: 1 RTT
>      Total == 2 RTT
> ...meanwhile, the same thing happens on m-1 other connections that the
> browser is using in parallel
>
> HTTP/1.1 with Upgrade to 2.0:
>      TCP handshake: 1 RTT
>      HTTP/1.1. request for resource 1: 1 RTT
>      HTTP/2.0 requests for resources 2, ..., n-1, n: 1 RTT
>      Total == 3 RTT
>
> More generally, the minimum number of round trips to fetch n small
> objects in current HTTP/1.1 usage is:
>    1+ CEILING(n/m) RTT
> where m is the number of concurrent connections the client uses
> (typically 6 or 8 for current-generation browsers.)  If a client used
> an initial HTTP/1.1 request to negotiate an upgrade to HTTP/2.0, the
> minimum number of round trips would be:
>    2 + n
>
> For n<=2*m, the Upgrade-based approach would mean more round trips
> than are required today.
>
> The Upgrade approach also would require more round trips than current
> SPDY usage:
>
> SPDY today:
>      TCP handshake: 1 RTT
>      TLS handshake, including NPN: 2 RTT
>      SPDY requests for resources 1, 2, ..., n-1, n: 1 RTT
>      Total = n resources in 4 RTT
>
> Initial HTTP/1.1 request + Upgrade:
>      TCP handshake: 1 RTT
>      TLS handshake: 2 RTT
>      HTTP/1.1 request w/Upgrade + response x/ 200 status: 1 RTT
>      SPDY requests for resources 2, ..., n-1, n  = 1 RTT
>      Total = n resources in 5 RTT
>
> In terms of sending an initial HTTP/1.1 request to upgrade to HTTP/2.0
> looks like a step backwards compared to current deployments of both
> HTTP/1.1 and SPDY.
>
> -Brian
>

-- 
Adrien de Croy - WinGate Proxy Server - http://www.wingate.com
WinGate 7 is released! - http://www.wingate.com/getlatest/
Received on Thursday, 1 March 2012 04:00:54 GMT

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