Internet Explorer Helper
- Martin Moghadam
- Youssef Benarab
- Henrik Wendt
The Internet Explorer Helper is a module loaded by Microsoft Internet Explorer (IE) that silently collects web page load times and sends it to the PerformanceGuard agent. The agent will then send the collected data to the DataCollector.
It's important to understand the difference between the web page load times measured by the IE module and the Response Time Measurements measured by the PerformanceGuard agent.
It's important to understand the difference between the web page load times measured by the IE module and the response times measured by the PerformanceGuard agent.
Response Time
The time elapsed between the last request packet has been sent and until the first reply packet is received from the server.
Web Page Load Time
The time elapsed between the navigation begins and until the entire page, including sub-elements such as images, is received from the server.
This means that the IE module will measure the time actually experienced by the user, while the PerformanceGuard agent measures the response time delivered by the server and network.
If the client computer is low on free resources, this may result in increased web page load time because Internet Explorer must compete with other running applications for resources, such as CPU time and free memory.
Data Collection
In order to collect any data from the IE module, at least one transaction filter of the type IE must be defined. Contrary to the PerformanceGuard agent HTTP transaction filters, IE filters will collect data for SSL (Secure Socket Layer) requests.
To prevent Internet Explorer from loading the IE module, set the agent configuration IEReport parameter to false.
Internet Explorer doesn't offer TCP/IP-specific data, such as packets/resets, etc., so these values are not collected by the IE module.
Value | PerformanceGuard Agent | IE Module |
---|---|---|
Response time | + | - |
Web page load time | - | + |
Sent trains / bytes / packets | + | - |
Received trains / bytes / packets | + | - |
Retransmissions | + (TCP only) | - |
Resets | + (TCP only) | - |
Histogram | + | + |
Server IP address | + | + |
Server port | + | + |
Framesets
Web pages made up of multiple documents, for example framesets, may result in incorrect web page load time.
A typical frameset, for example index.html, is made up of three individual pages:
- top.html
- menu.html
- main.html
When Internet Explorer starts downloading the pages in a frameset (top,menu and main -html), it reports that download of all the pages begins at the same time. This is, however, only correct if Internet Explorer is configured to allow as many connections to the server as there are pages in the frameset. In the example, Internet Explorer must allow three simultaneous server connections (one for each page), otherwise an incorrect web page download time will be reported for at least one of the pages.
If two server connections (the default) are allowed, what actually happens is:
- Internet Explorer reports download begin for top.html and begins download of the file
- Internet Explorer reports download begin for menu.html and begins download of the file
- Internet Explorer reports download begin for main.html
- Internet Explorer ends download of top.html
- Internet Explorer begins download of main.html
- Internet Explorer ends download of menu.html
- Internet Explorer ends download of main.html
For each page the reported web page download time is:
- top.html - the time elapsed between steps 1 and 4
- menu.htm correct - the time elapsed between steps 2 and 6
- main.html correct - the time elapsed between steps 3 and 7
There are two ways to overcome this:
- Don't define IE transaction filters that match any of the pages in a frameset.
- Adjust the registry keyHKEY_CURRENT_USER\\Software\\Microsoft\\Windows
CurrentVersion Internet Settings MaxConnectionsPerServer to allow as many server connections as required. If the key doesn't exist; the value defaults to two connections.
The same problem may occur with pages that contain iframes.
Response Time Versus Web Page Load Time
Response time is measured at the TCP/IP level while web page load time is measured at the application level (Internet Explorer).
A request is made for the html page index.html against a web server. The request consists of three TCP packets. After a short while the web server delivers the page in three TCP packets.
The response time is measured as the time elapsed between the last request packet and the first response packet.
The requested page contains the sub-element image.gif, after Internet Explorer has received index.html it will make a new request to the web server, this time asking for the file image.gif.
The web page load time is measured as the time between the initial request for index.html, and the completion of the request for image.gif.
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