Multi-modal network protocols : adapting to highly variable operating conditions

Most network protocols are uni-modal: they employ a single set of algorithms that allows them to cope well only within a narrow range of operating conditions. This rigid design renders these protocols inefficient in the face of widely varying operating environments or in conditions different from the ones for which they are optimized. Such uni-modal protocols have great difficulty in the mobile computing world where the operating conditions, including number of nodes, computational capabilities and rate of mobility, are not fixed. Consider, for example, routing in a network of ad-hoc nodes. Solutions like DSDV work well when the number of nodes is small. Unfortunately, such schemes scale poorly to larger population sizes. In such situations, more scalable algorithms that impose a structure on the network of ad-hoc nodes, in a manner similar to routing protocols in the Internet, provides better results. However, these scalable algorithms tend to incur high overheads in situations that DSDV handles well. Clearly, no single routing solution handles all situations that a node may encounter. Motivated by such examples, this paper attempts to answer the following question: Is it possible to redesign the traditional protocols to take on very different operating modes when faced with different environments? We present a case for such multi-modal protocols in our paper. Specifically, we discuss multi-modal reliability and routing. We show the feasibility of designing multi-modal protocols by describing how these protocols can make operating mode decisions and switch modes without additional overhead. This research was sponsored by DARPA under contract F30602-99-1-0518. Additional support was provided by IBM. Views and conclusions contained in this document are those of the authors and should not be interpreted as respresenting the official policies, either expressed or implied, of DARPA, IBM or the U.S. government. Computer Science Department, Carnegie Mellon University ([email protected]). Computer Science Department, Carnegie Mellon University ([email protected]) Computer Science Department, Carnegie Mellon University ([email protected]) Computer Science Department, Carnegie Mellon University ([email protected]). Report Documentation Page Form Approved OMB No. 0704-0188 Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number.