How does Android Market WebStore's Silent Install work? I have been thinking a lot about this, and came to a point that since the silent install requires the user to give his google id, it might fix a notification against that google id, to let the device associated with that id know that an application installation has to be done, and it has to start download of a particular app from the market. So that, when the device syncs the google id, it knows that it has to do some installation.

Since the device keeps polling the server for sync quite frequently, thus it knows about the installation almost instantly. In other words, the delays are negligible.

On the other note, I also thought that C2DM might have been used to do this, but since my personal device uses 2.1 and C2DM is available to devices having 2.2+, the possibility of use of C2DM is quite less.

Can anyone explain how it is being done?
Am I correct with my thoughts?

Update

I disabled Syncs in my phone and tried to install using Silent Install, and nothing happened. this way, I am coming closer to realise that my first opinion is correct.
On the other note, I also thought that
  C2DM might have been used to do this,
  but since my personal device uses 2.1
  and C2DM is available to devices
  having 2.2+, the possibility of use of
  C2DM is quite less.


It is actually quite plausible for 2.1 Market to use C2DM. GTalk, Gmail, and many other Google apps have always used C2DM internally (even before it's named C2DM). In 2.1, C2DM exist as GTalk Service. In 2.2, Google opened the C2DM API for external developers since they realized that 1) most app developers does not have the resources to create a reliable Push notification service, 2) a unified Push service would save battery, 3) Reliable instant Push service is a good selling point for Android.