Fiddler

Fiddler is useful to capture request and response for each URL. It’s very popular and easy to use tool. When you enable fiddler, make sure that HTTPS request should be capture. For that do following settings under “Tools --> Fiddler Option.

Following are some major finding/scenarios which can be identify using Fiddler.

Scenario	Check Point	Analysis	Probable Resolution
1	Check NLB and Server’s configuration Application has used NLB (Network Load Balancing) and there are more than two servers for load sharing. So request given by user may go any of one server. Best practice is to capture more than 20-30 same scenarios fiddler result. The main purpose of capturing same scenarios is to make sure that whatever load balancing done that works perfectly or not.	Check that if some specific requests in fiddler trace files takes more time comparison of rest of fiddler file or not. If yes then it clear cut indicate that either problem in NLB configuration or individual server confirmation.	Disable NLB, point to first server and capture fiddler result and same for other server. If any variation than check the individual server’s configuration. For example one IIS server has enable Static Compression on which other one is off. After identical both the server’s configuration, enable NLB and repeat test to capturing result for surety.
2	Check that for subsequent request In Web Site, images and CSS files store in local directory (cache) after first request to the server and subsequent request use cache images and CSS files. Due to this only payload for sub sequent request is low compare to first time request.	Fiddle gives “http response code”, it indicate that from where the files are coming. If application is hitting the server, http response code is 200 and for fetching from cache code is 302. Check that for subsequent request images, CSS and Js files should fetch from team directly not from the server.	Set the Caching properly to avoid server trip for sub sequent request. Example : for MOSS, enabled BlobCache in web.config file and other option in IIS for output caching.
3	Check for no of static Images	Check that how many images header contains and not dynamic. Even YSLOW can give the static for the no of images.	Club images for the less no of hits for the server.
4	Network delay and time taken statistic	Fiddle gives “Statistic” and “TimeLine” for all the request. Checked all the request which takes more time (1 Sec and more) and then check for “Statistic” and confirm that is there any delay due to network or not.	If fiddle shows the network delay, use the infrastructure tools which can give the exact information about where delay in network. Remove the unnecessary response generated by code to reduce the payload for request.

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