Comments on: Roundup on Parallel Connections http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/ Essential knowledge for making your web pages faster. Sat, 04 Feb 2012 09:46:28 +0000 hourly 1 http://wordpress.org/?v=3.2.1 By: Steve Souders http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/#comment-3668 Steve Souders Sat, 14 Jan 2012 16:31:12 +0000 http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/#comment-3668 @Boundless: You could try using different hostnames such as www1., www2., etc. @Boundless: You could try using different hostnames such as www1., www2., etc.

]]> By: Boundless http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/#comment-3667 Boundless Sat, 14 Jan 2012 16:20:02 +0000 http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/#comment-3667 Ah hah ! I forced my test page to only give 4 live streams instead of 8, and it works in Chrome and Safari. I then opened 2 additional streams, for a total of 6, and it's ok. But a 7th will not open. So Chrome and Safari are enforcing the 6-connection limit. I double checked this by closing one active stream, at which point the blocked 7th window showed video. How do I defeat this limit ??? Ah hah !

I forced my test page to only give 4 live streams instead of 8, and it works in Chrome and Safari. I then opened 2 additional streams, for a total of 6, and it’s ok. But a 7th will not open. So Chrome and Safari are enforcing the 6-connection limit. I double checked this by closing one active stream, at which point the blocked 7th window showed video.

How do I defeat this limit ???

]]> By: Boundless http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/#comment-3666 Boundless Sat, 14 Jan 2012 16:10:56 +0000 http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/#comment-3666 If the problem is due to the maximum number of connections per server, how can I circumvent it ? Can I have multiple ports to access a given media server, and distribute the load from a given page over them ? Would using different port numbers make my media server appear to be multiple servers ? Isn't Firefox enforcing the limit ? If the problem is due to the maximum number of connections per server, how can I circumvent it ? Can I have multiple ports to access a given media server, and distribute the load from a given page over them ? Would using different port numbers make my media server appear to be multiple servers ?

Isn’t Firefox enforcing the limit ?

]]> By: Boundless http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/#comment-3665 Boundless Sat, 14 Jan 2012 16:06:15 +0000 http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/#comment-3665 I have a custom media server whose job is to source MJPEG video streams from multiple cameras. It is intended for viewing several dozen cameras simultaneously at high frame rates in a single page. I have tested it with the latest Firefox with 8 cameras simultaneously in a single page, even when I open several additional video streams, and it is OK. But there is blocking in Chrome and Safari when I try to open additional pages using the same instance of the browser. There is a continuous connection for each camera since the video is live and therefore continuous. Is the problem with Chrome and Safari a result of the limit of the maximum number of connections per server ? But the tables show Firefox supports only 6, whereas more than 8 is OK. I have a custom media server whose job is to source MJPEG video streams from multiple cameras. It is intended for viewing several dozen cameras simultaneously at high frame rates in a single page. I have tested it with the latest Firefox with 8 cameras simultaneously in a single page, even when I open several additional video streams, and it is OK. But there is blocking in Chrome and Safari when I try to open additional pages using the same instance of the browser. There is a continuous connection for each camera since the video is live and therefore continuous.

Is the problem with Chrome and Safari a result of the limit of the maximum number of connections per server ? But the tables show Firefox supports only 6, whereas more than 8 is OK.

]]> By: Steve Souders http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/#comment-3491 Steve Souders Wed, 28 Sep 2011 20:12:10 +0000 http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/#comment-3491 @MNot: My attempt to highlight good blog posts from the past. ;-) @Jean-Philippe: I'm pretty sure request 1&3 would be considered the same hostname. @MNot: My attempt to highlight good blog posts from the past. ;-)

@Jean-Philippe: I’m pretty sure request 1&3 would be considered the same hostname.

]]> By: Jean-Philippe http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/#comment-3486 Jean-Philippe Wed, 28 Sep 2011 16:11:33 +0000 http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/#comment-3486 @steve In IE6, would these 3 URL be considered as distinct from the max connection perspective ? http://server1.xx?cgi (which map to 199.199.199.199) http://199.199.199.199?cgi http://?cgi (from a html which is on server1.xx) Thanks. @steve
In IE6, would these 3 URL be considered as distinct from the max connection perspective ?

http://server1.xx?cgi (which map to 199.199.199.199)
http://199.199.199.199?cgi
http://?cgi (from a html which is on server1.xx)

Thanks.

]]> By: Mark Nottingham http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/#comment-3198 Mark Nottingham Thu, 31 Mar 2011 21:46:55 +0000 http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/#comment-3198 Hah - just realised this is a really old post (about two years old!). You mentioned it on twitter and I assumed it was new. D'oh. Hah – just realised this is a really old post (about two years old!). You mentioned it on twitter and I assumed it was new. D’oh.

]]> By: Mark Nottingham http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/#comment-3197 Mark Nottingham Thu, 31 Mar 2011 21:46:00 +0000 http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/#comment-3197 Hey Steve, Almost two years ago, HTTPbis removed the connection limit, after discussion with browser vendors: http://trac.tools.ietf.org/wg/httpbis/trac/ticket/131 The problem with using too many connections isn't really server load; dealing with large numbers of conns server-side is fairly well-understood these days. The real problem is its effect on congestion control. E.g., if your browser uses 8 connections each to 10 sharded hosts, and the initial congestion window is a conservative 3, it means that about a third of a megabyte can be in flight, all at once, causing havoc for other applications. Jim Gettys was railing on this subject this week at IETF Prague; in combination with bufferbloat, it is unfriendly to other applications, as well as potentially worsening browse performance. Off to bed here, Hey Steve,

Almost two years ago, HTTPbis removed the connection limit, after discussion with browser vendors:
http://trac.tools.ietf.org/wg/httpbis/trac/ticket/131

The problem with using too many connections isn’t really server load; dealing with large numbers of conns server-side is fairly well-understood these days. The real problem is its effect on congestion control. E.g., if your browser uses 8 connections each to 10 sharded hosts, and the initial congestion window is a conservative 3, it means that about a third of a megabyte can be in flight, all at once, causing havoc for other applications.

Jim Gettys was railing on this subject this week at IETF Prague; in combination with bufferbloat, it is unfriendly to other applications, as well as potentially worsening browse performance.

Off to bed here,

]]> By: Steve Souders http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/#comment-2243 Steve Souders Fri, 30 Jul 2010 02:13:27 +0000 http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/#comment-2243 @John Rossen: There's overhead in establishing a new connection. The studies I did at Yahoo! found that too many simultaneous connections worsens performance. In most cases, it would be better to use fewer persistent connections. @John Rossen: There’s overhead in establishing a new connection. The studies I did at Yahoo! found that too many simultaneous connections worsens performance. In most cases, it would be better to use fewer persistent connections.

]]> By: John Rossen http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/#comment-2242 John Rossen Thu, 29 Jul 2010 19:35:16 +0000 http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/#comment-2242 n the post above, when you say “parallel connections”, its actually “parallel persistent connections” – right? Firefox allows max 15 connections per server (which are the “Connection:close” types), and max 6 “persistent” connections per server (“connection:keep-alive”). Since the max number of non “keep-alive” connections are more, is there a strong reason to go for persistent connections? If I serve 15 resources from a domain for my webpage, getting them all in parallel with “connection:close” should be faster than fetching them 6 at a time, with keep-alive tcp connections. Isn’t it? n the post above, when you say “parallel connections”, its actually “parallel persistent connections” – right?

Firefox allows max 15 connections per server (which are the “Connection:close” types), and max 6 “persistent” connections per server (“connection:keep-alive”). Since the max number of non “keep-alive” connections are more, is there a strong reason to go for persistent connections?

If I serve 15 resources from a domain for my webpage, getting them all in parallel with “connection:close” should be faster than fetching them 6 at a time, with keep-alive tcp connections. Isn’t it?

]]>