If a web page is made up of 2 main requests, say Request 1 and Request 2(i.e. 2 requests excluding sub-requesting for the images etc.) then how does a browser behave? Does it send Request 1, wait for a response and then send request 2 or does the browser send Request 1 and then send Request 2 without waiting for a response for Request 1. In other words does the browser send requests asynchronously or synchronously?
Load test tools playback requests in a sequential manner. Can we obtain the page response time by adding the response times for Request 1 and Request 2?
As for the way your tool handles the communication process- you may want to check with the manufacturer since some tools act as a certain version of a certain browser and that may effect the number of 'turns' (see article) that occur and the number of connections that the browser uses. Another factor is if your tool is set to use HTTP 1.0 or HTTP 1.1 protocols. The article will explain further.
the answer to your question depends on which browser you are using... Browsers use multiple threades for handling HTTP Requests. The standard used to be 4 threads. Now a lot of the new browser releases are using 2 threads.. and whenever you are talking HTTP 1.1, it usually uses 2 threads. Also remember if you embedded Java Applets or Active X controls, they will use a thread for a persistant connection, so be aware this will remove one thread from the rest of your HTTP processing.
Must of the load testing tools are creating scripts which you can edit each request (image, text,...) has been written as individual line in script. You can insert the wait line before them the wait can be depend on another request (wait until IMAGE A appears) or on time (wait 20 second. but remember in order to test the response time you should remove them all