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Re: p1-message-07 S 7.1.4

From: Adrien de Croy <adrien@qbik.com>
Date: Mon, 20 Jul 2009 09:35:04 +1200
Message-ID: <4A639188.5090502@qbik.com>
To: Henrik Nordstrom <henrik@henriknordstrom.net>
CC: HTTP Working Group <ietf-http-wg@w3.org>


Henrik Nordstrom wrote:
> lör 2009-07-18 klockan 15:46 +1200 skrev Adrien de Croy:
>
>   
>> But any client that only made 2 connections to a proxy would be quickly
>> dumped by users as basically unusable.  I think this para should be 
>> taken out.
>>     
>
> The user-agent limit is per accessed server (host component). There is
> no specified limit client->proxy when the client accesses multiple sites
>   

maybe need clarification then in 7.1.4, since it currently reads:

"A single-user client SHOULD NOT maintain more than 2 connections with 
any server or proxy."


> The limits are there to prevent unintentionall congestion and
> unfairness. Both of the server resources and network.
>   

It doesn't make any sense to me to try and address that issue in the 
protocol.

It's like we're defining a recipe for bread, and in the recipe we state 
nobody should own more than 2 loaves.

That is based on a whole series of assumptions about availability and 
capacity of resource, which even if they were valid now, will not be 
valid for all time.  Let alone the philisophical problems about whether 
HTTP should be trying to control that anyway.

Surely its up to a site to cater for the demand it gets.  Whether that's 
1 million clients each making 2 connections, or 100000 clients each 
making 20 connections.

It's up to ISPs to cater for demand they get.

Putting that should level requirement in the protocol has achieved only 
one thing:  problems for site designers coping with UAs that take it to 
heart.

Thankfully most UAs now ignore it.  The more UAs that ignore it, the 
fewer hoops site owners and authors will have to jump through to get 
around it.

> But yes, it's frequently a problem for certain types of sites, and the
> workaround of using multiple sitenames isn't exactly clean.
>
> I would propose adding a way where the HTTP server can grant it's
> clients to use more than 2 connections.
>
>   

Servers already send back an error page when they are overloaded.

Servers are free to limit connections in any way they wish.

Putting an arbitrary limit into the client can only do one thing - 
reduce user experience, something most site owners would rather not, 
which is why they set up so many different site names to get around the 
problem.

It also forces people to host on faster connections, because otherwise 
their lightly loaded site seems slow.

>> Furthermore the requirements that the second part places on a proxy
>> would greatly increase the complexity of the proxy, since it would then 
>> have to
>> start multiplexing requests from different client connections over the 
>> same server
>> connections.
>>     
>
> Why? The proxy is allowed to open two times the amount of client
> connections it sees with requests for the site. 
that's not how I read the following:

"A proxy SHOULD use up to 2*N connections to another server or proxy, 
where N is the number of simultaneously active users."

I read that as 2 connections per connected client.  Since the client can 
have 2 connections each, that's only 1 connection per client 
connection.  That wouldn't require multiplexing, but is a proxy deemed 
to be a client in this case?  In which case it can only have 2 
connections to any 1 server regardless of the number of connected clients.


> In reality this means
> that the proxy do not need to bother much about the limit unless it's
> proactively opening connections to a server or not pooling idle
> proxy<->nexthop persistent connections for reuse but randomly
> distributes client requests on many workers each with their own set of
> next-hop connections...
>   
some architectures don't lend themselves to that, esp those with 
filtering interfaces, where a filter may block execution for an 
indeterminate period.

Regards

Adrien

> Regards
> Henrik
>
>
>   

-- 
Adrien de Croy - WinGate Proxy Server - http://www.wingate.com
Received on Sunday, 19 July 2009 21:32:10 GMT

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