Delay tolerant networks (DTN) are characterized by intermittent connectivity, long delays and often constrained bandwidth. We consider mobile networks where node mobility and covert operation cause frequent disconnections. Nodes will see each other frequently but due to their movement, end-to-end paths do not remain stable long enough to complete a data transfer or even a simple data exchange, much less allow current congestion control protocols to react to these highly dynamic environments. To address the challenge of congestion control in DTNs we have implemented a novel congestion control mechanism based on the use of tokens. Network nodes must possess a token in order to inject messages into the network. Tokens are initially uniformly distributed but thereafter move randomly throughout the network. Using a discrete event simulator we show Token Based Congestion Control (TBCC) results in a reduction in the amount of dropped messages due to network congestion. In cases where drops are not allowed we add a constraint to the forwarding algorithm and show that network transit times are reduced by as much as 40% and total transit times, defined as the time from message generation until delivery to the destination, are reduced by 20%. We also show 36% reduction in the amount of intermediate network storage required. These results are significant since they show a reduction in both space (network storage) and time.
The advent of a widely interconnected computing infrastructure has raised the question of what kind of advanced communications can be implemented "in the network". The active networks concept explores such advanced capabilities such as content-based routing and multi-mode multicast. A larger issues exists, however, as to how widely distributed applications can access and manage any such advanced communication services. Hence, this paper investigates and demonstrates the use of network overlays to make active network services more accessible and easier to use. These overlays are discovered and the distributed applications are managed using grid computing tools. In this paper, we report on an HLA-compliant simulation that is started in a grid environment and uses a dynamic overlay of active network routers to accomplish scalable time management "in the network". We argue that this will be an effective, general mechanism for managing a variety of advanced communication services in distributed environments.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.