I have a page that depending on the data it is bringing back can take a very long time (minutes) to load, with the majority of this time spent in a method called from Page_Load(). I have noticed that once a certain time threshold is hit, Page_Load() will be hit a second time. When I started watching the network tabs in Chrome Dev Tools and Firebug I didn't see any second requests go out, but I did notice a few things:
In Firebug it temporarily flashes a status code of 407 for the long running request.
In the Chrome Timing tab it shows Stalled for several minutes, then Proxy Negotation right before Page_Load() is hit the second time.
What is going on here? I don't really know much about how proxies and authentication work, but it sure seems like there is some re-authentication going on in the middle of page load which is causing the whole page lifecycle to restart.