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#131: Connection limits (proposal)

From: Mark Nottingham <mnot@mnot.net>
Date: Mon, 19 Oct 2009 14:37:19 +1100
Message-Id: <1070C091-1F85-4DB7-9AF2-9A50716FCF5B@mnot.net>
To: HTTP Working Group <ietf-http-wg@w3.org>

OLD p1 7.1.4:

>   Clients that use persistent connections SHOULD limit the number of
>   simultaneous connections that they maintain to a given server.  A
>   single-user client SHOULD NOT maintain more than 2 connections with
>   any server or proxy.  A proxy SHOULD use up to 2*N connections to
>   another server or proxy, where N is the number of simultaneously
>   active users.  These guidelines are intended to improve HTTP  
> response
>   times and avoid congestion.


Clients (including proxies) SHOULD limit the number of simultaneous  
connections that they maintain to a given server (including proxies).

Previous revisions of HTTP gave a specific number of connections as a  
ceiling, but this was found to be impractical for many applications.  
As a result, this specification does not mandate a particular maximum  
number of connections, but instead encourages clients to be  
conservative when opening multiple connections.

In particular, while using multiple connections avoids the "head-of- 
line blocking" problem (whereby a request that takes significant  
server-side processing and/or has a large payload can block subsequent  
requests on the same connection), each connection used consumes server  
resources (sometimes significantly), and furthermore using multiple  
connections can cause undesirable side effects in congested networks.

Mark Nottingham     http://www.mnot.net/
Received on Monday, 19 October 2009 03:37:58 GMT

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