Large organizations often have users in multiple sites which are connected over the Internet. Since resources are limited, communication between these sites needs to be carefully orchestrated for the most benefit to the organization. We present a Mission-optimized Overlay Network (MON), a hybrid overlay network architecture for maximizing utility to the organization. We combine an offline and an online system to solve non-concave utility maximization problems. The offline tier, the Predictive Flow Optimizer (PFO), creates plans for routing traffic using a model of network conditions. The online tier, MONtra, is aware of the precise local network conditions and is able to react quickly to problems within the network. Either tier alone is insufficient. The PFO may take too long to react to network changes. MONtra only has local information and cannot optimize non-concave mission utilities. However, by combining the two systems, MON is robust and achieves near-optimal utility under a wide range of network conditions. While best-effort overlay networks are well studied, our work is the first to design overlays that are optimized for mission utility.

Wireless researchers face the practical challenge of evaluating the performance of new routing protocols for very large-scale heterogeneous mobile systems. While simulation platforms, tools and techniques have matured, doubts remain about the broad validity of simulated results when applied to real world situations. Wireless network emulation provides a middle ground between simulations and real-world testing. However, emulation environments are complex to run and cost-prohibitive for larger-scale tests. In order to maximize fidelity while managing complexity and costs, we developed a common framework that unifies simulation-based analysis and emulation experiment tools, in order to produce calibrated and scalable performance evaluations.

Subset difference revocation (SDR) provides a powerful mechanism for the efficient expression of the revocation state of a large group of key recipients. However, arbitrary assignment of receivers as leaf nodes in a static binary tree can lead to inefficiencies in certain group revocation states. Gateway subset difference revocation (GSDR), developed in our ongoing SecureKeys effort, provides the ability to group receivers based upon organizational characteristics while simultaneously introducing the ability to audit rekey and data transmission, delegate rekey decisions to subordinate decision makers, and override subordinate rekey authority when necessary. GSDR extends the existing SDR scheme by deploying rekey gateways in a hierarchy that mimics an organic decision making structure. Delegation of rekey authority offloads a significant computational and communications burden from gateways high in the tree, while correspondingly partitioning the rekey traffic required to be processed by leaf nodes in the tree. GSDR also significantly reduces label storage requirements in rekey devices by limiting terminal node fan-out

This paper describes a novel application of subband coding to the MPEG-I video compression algorithm. This scheme yields a higher signal-to-noise ratio at a fixed bit rate compared to existing techniques such as truncation. Simulations performed both with and without motion compensation illustrate the improved subjective visual quality as well as the temporal behavior of the video. Furthermore, these performance gains are unaffected by motion compensation and, hence, can be exploited by any MPEG coder. The algorithm has direct practical significance for layered video coding applications and telecommunications.>

Successful exploitation of prioritized ATM networks requires matching the characteristics of the coded source with the unique properties of the network. This is particularly true for video which is very bandwidth intensive. The authors describe and investigate the performance of three prioritization schemes in terms of the traffic characteristics, SNR, and visual quality. These schemes are further designed such that the high priority data stream is MPEG-I compliant and only a single pass through the encoder is required. A technique for choosing parameter values which achieve a specified high priority traffic bandwidth is presented for two of these schemes. The technique is demonstrated to be remarkably accurate for different video sequences.>