Mobile IPv6 on the Linux Watch (shown at LinuxWorld August 2002)

In this demo a server streams image data to the watch using TCP over IPv6. The Linux Watch is attached to its cradle with a serial cable. A PPP connection between an access point and the cradle provides IP connectivity. The watch can be moved from one access point to another by detaching the serial cable and attaching it at the new station. This demonstration shows the mobility of the watch, persistent IP connectivity and the fact that Linux can provide network connectivity to small devices.

As shown in the above figure our demonstration setup consisted of two laptops that served as routers, routing IP packets between their Ethernet interfaces and PPP running on their serial ports. One of these laptops was the home router and the was the foreign router. The Linux Watch made PPP connections with either the home or the foreign router when its serial cable was connected to them.

We decided to demonstrate mobility in action by showing a single TCP connection that stayed alive even as the Watch was disconnected from its home router and connected to a foreign router and back. Because TCP connections are hard to visualize, we created an application that showed a continuous slideshow on the Watch display, repeatedly fetching different still images over a TCP socket connection, and displaying them on the Watch face. Conceptually, a third machine was the server that serveed up the still images to the Watch, but for the demo we simply ran the server program on one of the two laptops that served as routers. When the serial cable from the Watch was disconnected from the home router (laptop), the still image data over the TCP connection was interrupted and the slideshow stopped advancing. When the Watch was then connected to the foreign router (laptop), this router reestablished its persistent PPP connection with the Watch and the Watch discovers that it has now moved to a foreign location. This movement detection is achieved through Mobile IPv6 signaling mechanisms and in this process the Watch did a registration with the HA (foreign router) and also performed route optimization with the Correspondenc Node (which in this case happened to be the Home Agent itself). Thus, it ensured that the slideshow data packets got routed to the foreign location. All of this takes a couple of seconds and once the data flow over the TCP connection resumed, the slideshow continued from where it was stalled. The TCP connection remained oblivious to the fact that the Watch moved from one router to another.

Over time, we expect this to work wireless interfaces such as Bluetooth™.

Some external coverage on this topic can be found here.

More details are available in a paper published in Fosdem 2004.

Page was last updated in Feb, 2004.