maximum concurrent connections in browsers

When we say the maximum concurrent connections allowed in browsers, are we saying per browser or per tab? e.g in IE 6, the limit is 2. If I open two IE 6 windows, both of the web page contains a persistent iframe connection, do开发者_运维知识库es it mean that if i open the third IE 6 window, the iframe persistent connection can't be connected?

However, I tried and it still can connect to the same server. So does this mean that the concurrent connection limit is 2 per windows in IE 6?

IE 6 isn't Firefox. Every window is its own process. So yes, I guess you get the configured number of concurrent connections (does not need to be 2, as you can trivially change that in the registry) per window, i.e. per process.

There are concurrent connection limits per host, this is dependent on the both HTTP protocol (1.1 or 1.0) used and the client bandwidth available (broadband or dial-up), see the Concurrent Connectons section in AJAX - Connectivity Enchancements article over at MSDN for details.