The purpose of the Travler project was to produce an integrated systems software package to support the special needs of mobile computing.

Approach

Travler built an integrated package of systems software services that would fill important needs for mobile computer users. The Travler approach integrated those services that already existed in reasonable forms (or could be expected to, in the near future), such as wireless communications protocols, secure transmission of data, and authentication services. Other components were produced by the project and built into the Travler framework. These included the following:

Scalable support for portable replication services. These services allow replication of files between mobile computers and stationary computers. By providing high scale in numbers of replicas and users, this service enables widespread data-sharing. The quick, low-cost, flexible characteristics of the implementation would also encourage mobile users to perform more cooperative work on an ad hoc basis.

Predictive hoarding of files. This service predictively hoards any files a mobile computer user might need while disconnected from any network, or even while poorly connected. It works automatically, predicting and transparently storing all files the user will need during his disconnection. The early implementation (Seer) shows improvements of up to orders of magnitude of disk space required over previous solutions, and puts much less burden on its users.

Virtual networking. This service offers systems support for applications to adapt to the changing communications characteristics of a mobile computer, making effective use of whatever bandwidth is currently available, without restarting applications or requiring user assistance. It will also provide adaptation by recognizing particular types of data streams and applying suitable modifications to them, using an adaptive agent framework to place proxy agents appropriately throughout the network to support communications streams. We are also investigating application adaptations to handle changing conditions for the user, particularly in the context of Web browsing (Smiley).

Power management facilities based on task migration. This service allows untethered mobile machines connected by wireless networks to transparently migrate power-expensive computations to tethered servers. Early results show the possibility of up to a five-fold increase in portable computer battery life through this technique.

Real-time modeling and simulation. This service allows mobile machines to model and/or simulate their current environment. The results can be fed to any other system components, improving the ability to deal with changing conditions. Control of replication services will be an early test of this system.

Modeling and simulation environment for mobile computing software. This environment allows developers to make quick and inexpensive tests of new ideas for mobile computing software by providing a suite of models and simulations that already understand a large part of the environment. It allows for scaling analysis not possible in normal deployments, and includes a hybrid simulation technique that saves the effort of simulating components that already exist.

Related Research

The Travler research team has performed on several DARPA-funded related efforts: Filing and Data Management Environments (Ficus), Secure, Bilateral Replicated Distributed Filing (Truffles and User-Level Truffles), and Adaptive Mobile Information Systems (WAMIS). Part of this same team worked on another DARPA-funded effort entitled "A Middleware Framework for Supporting Application Use of Active Networks (PANDA).

Important Papers

Research team members published several important papers that directly relate to work currently underway on Travler.

Software Download

Important software created under the Travler project is available for download.