In tip 284, I described the RAS AutoDisconnect and IdleHangUpSeconds registry entries.

When using Microsoft Proxy Server, RAS may fail to disconnect due to the following reasons:

- A Winsock application on a client is open and connected to the Internet.

- A Web Proxy client (Web Browser) is left open and connected to a Web Page that contains a refresh tag.

- The active caching feature of the Web Proxy service is updating the cache.

- Other TCP/IP traffic is present on the modem connection from the Internet. For example,
  some Internet service providers may send router messages to your server while
  it is connected to the Internet. Network Monitor can be used to verify if this is the reason.

- PPP LCP extensions are enabled. Disable them in the phonebook entry on the Server tab
  to prevent LCP packets from resetting the autodisconnect timer.

- The WINS Client is bound to the External Network Adapter. Unbind it in
  Control Panel / Network / Bindings / all adapters. Click the + sign next to
  Remote Access WAN Wrapper to expand it.
  Select WINS client (TCP/IP) and click Disable.

- Remote Access AutoDial Manager is started. Disable it in Control Panel / Services.

- The IdleHangUpSeconds values are < 60 seconds. Increase them to 60 seconds.