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, 20 Mar 2010 09:37:54 +0000 http://wordpress.org/?v=2.9.1 hourly 1 By: Steve Souders http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/comment-page-1/#comment-1196 Steve Souders Sat, 05 Dec 2009 08:31:31 +0000 http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/#comment-1196 @Manjusha: Yes, Firefox 3+ allows 6 _persistent_ connections per hostname. You generally want to do persistent connections. It's likely slower to establish 15 connections than to re-use 6 connections. Exact results depends on the user's network conditions. At some point, no matter how many connections you open in parallel, there's a limit to the available bandwidth capacity. Also, latency and packet loss come into play. @Manjusha: Yes, Firefox 3+ allows 6 _persistent_ connections per hostname. You generally want to do persistent connections. It’s likely slower to establish 15 connections than to re-use 6 connections. Exact results depends on the user’s network conditions. At some point, no matter how many connections you open in parallel, there’s a limit to the available bandwidth capacity. Also, latency and packet loss come into play.

]]> By: Manjusha http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/comment-page-1/#comment-1192 Manjusha Sat, 05 Dec 2009 00:20:28 +0000 http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/#comment-1192 Thanks Steve for all these wonderful posts and the HPWS book. In the post above, when you say "parallel connections", its actually "parallel persistent connections" - right? Firefox 3.5 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? Thanks Steve for all these wonderful posts and the HPWS book.

In the post above, when you say “parallel connections”, its actually “parallel persistent connections” – right?

Firefox 3.5 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?

]]> By: Richard Wang http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/comment-page-1/#comment-1161 Richard Wang Wed, 02 Dec 2009 13:41:47 +0000 http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/#comment-1161 I found that using Fiddler would actually defeat adding more concurrent connections by adding sub domains. I ran into this in my debugging. I had a web app that sends requests to two sub domains for the purpose of increasing concurrent connections to 4 for IE7. But in Fiddler, I found the max concurrent connections are only 2, meaning two requests to a.foo.com will block a request to b.foo.com. My interpretation of this phenomenon is Fiddler serves as a proxy to IE7. Therefore, when Fiddler is used, all HTTP requests, no matter which domains they are sent to, are forced to the same Fiddler proxy destination. Therefore, they are all counted towards the 2 max concurrent connections limit. I found that using Fiddler would actually defeat adding more concurrent connections by adding sub domains.

I ran into this in my debugging. I had a web app that sends requests to two sub domains for the purpose of increasing concurrent connections to 4 for IE7. But in Fiddler, I found the max concurrent connections are only 2, meaning two requests to a.foo.com will block a request to b.foo.com.

My interpretation of this phenomenon is Fiddler serves as a proxy to IE7.
Therefore, when Fiddler is used, all HTTP requests, no matter which domains
they are sent to, are forced to the same Fiddler proxy destination. Therefore,
they are all counted towards the 2 max concurrent connections limit.

]]> By: Sam Foster http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/comment-page-1/#comment-861 Sam Foster Tue, 29 Sep 2009 11:03:03 +0000 http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/#comment-861 @Steve: thank you and thank you. I'm not clear how/why a proxy would have this effect on IE6, but that uncertainty exists at all there is enough. I'm signed up to the Exceptional Perf. group, see you there. @Steve: thank you and thank you. I’m not clear how/why a proxy would have this effect on IE6, but that uncertainty exists at all there is enough. I’m signed up to the Exceptional Perf. group, see you there.

]]> By: Steve Souders http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/comment-page-1/#comment-860 Steve Souders Tue, 29 Sep 2009 05:23:43 +0000 http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/#comment-860 @Sam: I tested that URL in IE and only see two parallel connections. Keep in mind that Charles and Fiddler are proxies, and change the download behavior of browsers. (See the section above on "Effect of Proxies".) You should subscribe to Exceptional Performance in Yahoo! Groups. It's a great mailing list for these types of questions. @Sam: I tested that URL in IE and only see two parallel connections. Keep in mind that Charles and Fiddler are proxies, and change the download behavior of browsers. (See the section above on “Effect of Proxies”.) You should subscribe to Exceptional Performance in Yahoo! Groups. It’s a great mailing list for these types of questions.

]]> By: Sam Foster http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/comment-page-1/#comment-859 Sam Foster Mon, 28 Sep 2009 15:59:43 +0000 http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/#comment-859 @Steve, I'm looking for a forum/group/mailing-list to discuss this stuff, do you have/know of one? /Sam @Steve,

I’m looking for a forum/group/mailing-list to discuss this stuff, do you have/know of one?

/Sam

]]> By: Sam Foster http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/comment-page-1/#comment-858 Sam Foster Mon, 28 Sep 2009 15:56:37 +0000 http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/#comment-858 @Steve Souders One example: http://www.thepopcornfactory.com/occasion/fall.category.20752.70002 I get parallel requests for: http://www.thepopcornfactory.com/wcsstore/ThePopcornFactory/images/1800flowers.jpg http://www.thepopcornfactory.com/wcsstore/ThePopcornFactory/images/mslo.gif http://www.thepopcornfactory.com/wcsstore/ThePopcornFactory/images/cherylco.jpg http://www.thepopcornfactory.com/wcsstore/ThePopcornFactory/images/fanniemay.jpg But this isnt isolated, I see it across the site. Haven't yet tested the sister sites, but wouldnt be surprised to find the same thing there. @Steve Souders

One example:
http://www.thepopcornfactory.com/occasion/fall.category.20752.70002

I get parallel requests for:
http://www.thepopcornfactory.com/wcsstore/ThePopcornFactory/images/1800flowers.jpg
http://www.thepopcornfactory.com/wcsstore/ThePopcornFactory/images/mslo.gif
http://www.thepopcornfactory.com/wcsstore/ThePopcornFactory/images/cherylco.jpg
http://www.thepopcornfactory.com/wcsstore/ThePopcornFactory/images/fanniemay.jpg

But this isnt isolated, I see it across the site. Haven’t yet tested the sister sites, but wouldnt be surprised to find the same thing there.

]]> By: Steve Souders http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/comment-page-1/#comment-857 Steve Souders Mon, 28 Sep 2009 15:21:15 +0000 http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/#comment-857 @Sam: Can you provide a URL? @Sam: Can you provide a URL?

]]> By: Sam Foster http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/comment-page-1/#comment-856 Sam Foster Mon, 28 Sep 2009 11:29:13 +0000 http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/#comment-856 I've been testing a site and have seen 4 concurrent connections in IE6 to the same domain (there's no sharding or CDN used, everything comes from the app server) To clarify, in the waterfall chart (I've checked w. Charles and Fiddler) I see 4 requests going out for images that overlap. The same site in IE7 uses just 2 connections. The requests are http 1.1, I've checked my registry and afaict its factory default - no tweaks to MaxConnectionsPerServer REG_DWORD (or MaxConnectionsPer1_0Server REG_DWORD) I'm not sure if this is a test environment anomally, or a clever trick I need to know about! I’ve been testing a site and have seen 4 concurrent connections in IE6 to the same domain (there’s no sharding or CDN used, everything comes from the app server)

To clarify, in the waterfall chart (I’ve checked w. Charles and Fiddler) I see 4 requests going out for images that overlap. The same site in IE7 uses just 2 connections.

The requests are http 1.1, I’ve checked my registry and afaict its factory default – no tweaks to MaxConnectionsPerServer REG_DWORD (or MaxConnectionsPer1_0Server REG_DWORD)

I’m not sure if this is a test environment anomally, or a clever trick I need to know about!

]]> By: Steve Souders http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/comment-page-1/#comment-126 Steve Souders Tue, 29 Apr 2008 04:47:59 +0000 http://www.stevesouders.com/blog/2008/03/20/roundup-on-parallel-connections/#comment-126 tad - I created a Cuzillion page to test this: http://stevesouders.com/cuzillion/?c0=bi2hfff2_0&c1=bi2hfff2_0&c2=bi2hfff2_0&c3=bi2hfff2_0&c4=bi2hfff2_0&c5=bi2hfff2_0&c6=bi2hfff2_0&c7=bi2hfff2_0&c8=bi2hfff2_0 On Opera 9.27 using the default values ("Max Connections Server" is 8) downloads 4 resources in parallel for a single hostname. If you uncheck "Reduce Max Persistent HTTP Connections" it drops to 2 in parallel. If recheck that and raise "Max Connections Server" to 16 it downloads 8 in parallel. Perhaps this is a terminology gap but the default behavior is 4 in parallel. tad – I created a Cuzillion page to test this:

http://stevesouders.com/cuzillion/?c0=bi2hfff2_0&c1=bi2hfff2_0&c2=bi2hfff2_0&c3=bi2hfff2_0&c4=bi2hfff2_0&c5=bi2hfff2_0&c6=bi2hfff2_0&c7=bi2hfff2_0&c8=bi2hfff2_0

On Opera 9.27 using the default values (“Max Connections Server” is 8) downloads 4 resources in parallel for a single hostname. If you uncheck “Reduce Max Persistent HTTP Connections” it drops to 2 in parallel. If recheck that and raise “Max Connections Server” to 16 it downloads 8 in parallel. Perhaps this is a terminology gap but the default behavior is 4 in parallel.

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