1. Customer is testing different webhosts by redirecting DNS using HOSTS file.
2. Customer has observed exceptionally slow uploads in the redirected DNS specifically for the Flash uploaded content
The explanation that the webhost came back with was that Flash plugin or our SWF code was somehow caching the DNS response - actually, we received a lecture on how what we were doing was incredibly dangerous and that we should revert to using the native DNS libraries rather than caching old data. My first reaction is to say that the webhost's explanation is ridiculous as Flash plugin is surely just a client of the browser / os network layer. Certainly, we have not modified (and would have no reason to modify) the network layer in any way whatsoever. If it is Flash related, then it would need to be something pretty esoteric in code which we are using but haven't written, such as the AMF services...
However, I haven't got an alternative explanation for the observed data. The only result I found in extensive googling was a single instance where an IE proxy server setting appeared to be ignored for specific types of content in a specific browser version running in a highly modified private network.
Has anybody encountered / resolved issues with Flash plugin apparently failing to respect DNS behaviour modification? I imagine it must be somewhere lower down? Perhaps browser making requests through an unusual pathway? Something else?
Any ideas welcome.