I’m Greg Scott and I work as a developer on a team that provides core networking technologies on Windows Mobile.  There has been some [negative] feedback from the community about Bluetooth dial-up networking (DUN) being removed in WM5 AKU3.  I’ll do my best to explain that.


Internet [Connection] Sharing


In WM5 AKU3 we introduced a new application called “Internet Sharing”.  The technology behind this is actually referred to as Internet Connection Sharing (ICS).  But our usability folks decided to drop the word “Connection” since it didn’t fit nicely in the user interface.


ICS is something we’ve shipped as a component in the Windows CE operating system for several releases.  We have now brought this technology to Windows Mobile.  ICS allows you to share a public network connection (cellular data) with a private network connection (Bluetooth PAN or USB).  The phone is basically acting like a your home’s wireless router.


Modem Link


Before Internet Sharing, we shipped an application called Modem Link.  This application enables some of the same functionality provided by ICS.  Modem Link supported sharing the cellular data connection over USB, IrDA, or Bluetooth.  For Bluetooth, the DUN profile was used.


Instead of sharing the Internet connection at the IP layer, as ICS does, Modem Link enables the PC to directly send commands to the cellular radio on the device.


How is Internet Sharing better?


ICS is superior to the modem link technology in several ways.


1)      Usability: With Modem Link, users need to enter dial strings (e.g. *99#) to connect their PC to the Internet.  This is not necessary with Internet Sharing.

2)      Uninterrupted connectivity: ICS can continue to be connected when you get an incoming voice call.  Modem Link will give up the cellular radio for the phone to answer the voice call.  Internet Sharing will stay connected in this scenario.  On some cellular networks it is not able to send or receive data.  The cellular network needs to support simultaneous voice/data to provide the best user experience.  This is supported on 3G networks.

3)      Full connectivity: When you are connected over ICS, the applications on your device (e.g. ActiveSync) remain connected to the Internet.  This is not the case with Modem Link.

4)      Future enhancements: Unfortunately I’m not allowed to discuss new features we are planning.  But you can probably imagine some of the new features we can add with a fully IP-based solution.

5)      Compatibility with future cellular radio technology.  New cellular radios are supporting an IP packet-based interface as opposed to the legacy serial-based interface.  Modem Link and Bluetooth DUN are dependent on the legacy serial interface but Internet Sharing can function over either interface.


So far we have gotten mostly positive feedback about Internet Sharing. Most people have commented that it “just works” compared to the process of setting up your phone as a modem with Modem Link.


With that said, we have gotten some feedback that ICS usability is actually worse in some cases.  The Internet Sharing app requires that the user first “connect” ICS before connecting Bluetooth PAN from the PC.  With DUN you could initiate everything from the PC side.  This is something we’ll work on improving in the future.


But why did we remove Bluetooth DUN?


So you may be thinking, ok, Internet Sharing is really cool but why did you need to remove Bluetooth DUN?!?  My car kit or Mac does not support Bluetooth PAN and I relied on this legacy technology.


Actually, Microsoft did not remove Bluetooth DUN completely.  We still ship this technology to our OEMs.  It is included in an optional package that OEMs and operators can decide to ship on a per device basis.  Internet Sharing is also in an optional package.  We did change one thing though.  Internet Sharing is included by default and Bluetooth DUN no longer is.


Bluetooth DUN is a legacy technology that is likely to disappear over time.  Especially when you look at the great experience Internet Sharing provides with Bluetooth PAN.  It also does not make sense for cellular radios to continue supporting a legacy interface just to enable Bluetooth DUN.  In the past we received a lot of criticism about Modem Link, especially related to usability.  For this reason we decided not to include it by default.


Anyway, based on continued feedback from the community, we have changed our minds!  We will bring Bluetooth DUN back by default in a future WM6 AKU release.  Keep in mind that OEMs and operators still have the final say whether DUN will end up on a specific device.




So, please give us your feedback.  We’d love to hear what new features you’d like to see in Internet Sharing, whether you’ve had a good or bad experience, etc.  Thanks!