The technology advancement has made Unmanned Aerial Vehicle (UAV) swarm a promising method to achieve complicated missions that a single UAV cannot support. Leader-followers formation is a widely used swarm management scenario where a leader drone frequently broadcasts controlling messages to all follower drones to achieve collaboratively a common mission. However, managing such a UAV swarm, especially when the member drones dynamically join and leave the swarm, introduces significant security challenges and performance overhead.In this work, we propose a Swarm Broadcast Protocol (SBP) to facilitate the security protection of leader-followers formation based UAV swarms. SBP contains a security key management scheme that manages a broadcast key among the swarm for leader to broadcast encrypted messages to followers. When swarm membership changes, the broadcast key will be updated and synchronized among the swarm to maintain both backward and forward secrecy. The overhead of SBP is small that only constant computational overhead is needed for both swarm leader and followers to achieve key synchronization when a new drone joins regardless of the current swarm size. This feature would highly reduce the overhead when there are many individual drone joining events. Through experiments on network emulator, we show that SBP achieves lowest bandwidth overhead and CPU utilization to handle multiple swarm membership changing events, comparing with two public-key-based swarm management protocol baselines.

Unmanned Aerial Vehicles (UAVs) are becoming more popular than ever in outdoor commercial services. Many third-party UAV companies offer their UAVs as mobile data collectors to assist their clients in remote data collection missions. However, due to the lack of trust and transparency, the clients often have very little control on the behavior of these UAVs. This issue is even exacerbated if the service had to deal with private client data. In this work, we propose a solution that enables third-party UAVs to collect and process private client data from remote data sites in a trustworthy and efficient manner. We design and implement the Secure Homomorphic Encryption (SHE) framework. SHE combines trusted hardware enclave and homomorphic encryption technologies to provide strong privacy primitives on client data. SHE features in a recrypt technique such that the computation and communication overhead for homomorphic encryption on the client data is minimized. In addition, SHE takes the advantage of UAVs' travelling time to run data aggregation tasks in order to speed-up data processing. Through laboratory experiments, we demonstrate that SHE can meet the performance requirement in many common data processing and aggregation missions. SHE thus can be introduced as a trustworthy framework for the third-party UAV service providers.

The dramatic success and scaling of the Internet was made possible by the core principle of keeping it simple in the middle and smart at the edge (or the end-to-end principle). However, new applications bring new demands, and for many emerging applications, the Internet paradigm presents limitations. For applications in this new generation of Internet services, structured overlay networks offer a powerful framework for deploying specialized protocols that can provide new capabilities beyond what the Internet natively supports by leveraging global state and in-network processing. The structured overlay concept includes three principles: A resilient network architecture, a flexible overlay node software architecture that exploits global state and unlimited programmability, and flow-based processing. We demonstrate the effectiveness of structured overlay networks in supporting today's demanding applications and propose forward-looking ideas for leveraging the framework to develop protocols that push the boundaries of what is possible in terms of performance and resilience.

This paper presents the first hierarchical byzantine fault-tolerant replication architecture suitable to systems that span multiple wide-area sites. The architecture confines the effects of any malicious replica to its local site, reduces message complexity of wide-area communication, and allows read-only queries to be performed locally within a site for the price of additional standard hardware. We present proofs that our algorithm provides safety and liveness properties. A prototype implementation is evaluated over several network topologies and is compared with a flat byzantine fault-tolerant approach. The experimental results show considerable improvement over flat byzantine replication algorithms, bringing the performance of byzantine replication closer to existing benign fault-tolerant replication techniques over wide area networks.

Wireless mesh networks extend the connectivity range of mobile devices by using multiple access points, some of them connected to the Internet, to create a mesh topology and forward packets over multiple wireless hops. However, the quality of service provided by the mesh is impaired by the delays and disconnections caused by handoffs, as clients move within the area covered by multiple access points. We present the architecture and protocols of SMesh, the first transparent wireless mesh system that offers seamless, fast handoff, supporting real-time applications such as interactive VoIP. The handoff and routing logic is done solely by the access points, and therefore connectivity is attainable by any 802.11 device. In SMesh, the entire mesh network is seen by the mobile clients as a single, omnipresent access point, giving the mobile clients the illusion that they are stationary. We use multicast for access points coordination and, during handoff transitions, we use more than one access point to handle the moving client. SMesh provides a hybrid routing protocol that optimizes routes over wireless and wired links in a multihomed environment. Experimental results on a fully deployed mesh network demonstrate the effectiveness of the SMesh architecture and its intra-domain and inter-domain handoff protocols.

This paper presents an architecture and a hybrid routing protocol for multi-homed wireless mesh networks that provide uninterrupted connectivity and fast handoff. Our approach integrates wireless and wired connectivity, using multicast groups to coordinate decisions and seamlessly transfer connections between several Internet gateways as mobile clients move between access points. The protocol optimizes the use of the wireless medium by short-cutting wireless hops through wired connections, paying a very low overhead during handoffs. The paper demonstrates that inter-domain handoffs occur instantaneously, with virtually no loss or delay, for both TCP and UDP connections.

This paper presents the first hierarchical Byzantine fault-tolerant replication architecture suitable to systems that span multiple wide area sites. The architecture confines the effects of any malicious replica to its local site, reduces message complexity of wide area communication, and allows read-only queries to be performed locally within a site for the price of additional hardware. A prototype implementation is evaluated over several network topologies and is compared with a flat Byzantine fault-tolerant approach

Abstract — This paper presents the architecture and protocols of SMesh, a completely transparent wireless mesh system that offers seamless, fast handoff, supporting VoIP and other real-time application traffic for any unmodified 802.11 device. In SMesh, the entire mesh network is seen by the mobile clients as a single, omnipresent access point. Fast handoff is achieved by ensuring that each client is served by at least one access point at any time. Mobile clients are handled by a single access point during stable connectivity times. During handoff transitions, SMesh uses more than one access point to handle the moving client. Access points continuously monitor the connectivity quality of any client in their range and efficiently share this information with other access points in the vicinity of that client to coordinate which of them should serve the client. Experimental results on a fully deployed mesh network consisting of 14 access points demonstrate the effectiveness of the SMesh architecture and its handoff protocol. I.

The cost savings and novel features associated with voice over IP (VoIP) are driving its adoption by service providers. Unfortunately, the Internet's best effort service model provides no quality of service guarantees. Because low latency and jitter are the key requirements for supporting high-quality interactive conversations, VoIP applications use UDP to transfer data, thereby subjecting themselves to quality degradations caused by packet loss and network failures. In this paper, we describe an architecture to improve the performance of such VoIP applications. Two protocols are used for localized packet loss recovery and rapid rerouting in the event of network failures. The protocols are deployed on the nodes of an application-level overlay network and require no changes to the underlying infrastructure. Experimental results indicate that the architecture and protocols can be combined to yield voice quality on par with the public switched telephone network

The cost savings and novel features associated with Voice over IP (VoIP) are driving its adoption by service providers. Such a transition however can successfully happen only if the quality and reliability offered is comparable to the existing PSTN. Unfortunately, the Internet's best effort service model provides no inherent quality of service guarantees. Because low latency and jitter is the key requirement for supporting high quality interactive conversations, VoIP applications use UDP to transfer data, thereby subjecting themselves to performance degradations caused by packet loss and network failures.In this paper we describe two algorithms to improve the performance of such VoIP applications. These mechanisms are used for localized packet loss recovery and rapid rerouting in the event of network failures. The algorithms are deployed on the routers of an application-level overlay network and require no changes to the underlying infrastructure. Initial experimental results indicate that these two approaches can be composed to yield voice quality on par with the PSTN.

When many parties share network resources on an overlay network, mechanisms must exist to allocate the resources and protect the network from overload. Compared to large physical networks such as the Internet, in overlay networks the dimensions of the task are smaller, so new and possibly more effective techniques can be used. In this work we take a fresh look at the problem of flow control in multisender multigroup reliable multicast and unicast and explore a cost-benefit approach that works in conjunction with Internet standard protocols such as TCP. In contrast to existing window-based flow control schemes, we avoid end-to-end per sender or per group feedback by looking only at the state of the virtual links between participating nodes. This produces control traffic proportional only to the number of overlay network links and independent of the number of groups, senders, or receivers. We show the effectiveness of the resulting protocol through simulations and validate the simulations with live Internet experiments. We demonstrate near-optimal utilization of network resources, fair sharing of individual congested links, and quick adaptation to network changes.

Reliable point-to-point communication is usually achieved in overlay networks by applying TCP on the end nodes of a connection. This paper presents a hop-by-hop reliability approach that considerably reduces the latency and jitter of reliable connections. Our approach is feasible and beneficial in overlay networks that do not have the scalability and interoperability requirements of the global Internet. The effects of the hop-by-hop reliability approach are quantified in simulation as well as in practice using a newly developed overlay network system that is fair with the ex-ternal traffic on the Internet. The experimental results show that the overhead associated with overlay network process-ing at the application level does not play an important fac-tor compared with the considerable gain of the approach. 1

Group communication systems are proven tools upon which to build fault-tolerant systems. As the demands for fault-tolerance increase and more applications require reliable distributed computing over wide area networks, wide area group communication systems are becoming very useful. However, building a wide area group communication system is a challenge. This paper presents the design of the transport protocols of the spread wide area group communication system. We focus on two aspects of the system. First, the value of using overlay networks for application level group communication services. Second, the requirements and design of effective low latency link protocols used to construct wide area group communication. We support our claims with the results of live experiments conducted over the Internet.

Real time transactions are implemented by client-server applications, which must have a very good response time and which are particularly difficult to realize. We have created three instruments used for developing multi user software products that manage geographically distributed data. Client users have a graphical display of the database placed on the server (actually they have the data displayed on a map) and then can easily make queries by selecting with a mouse the region or the object in which they are interested. Multiple users can access the database concurrently for reading and updating by network, modem or serial cable.

The paper presents an integrated system designed for the agglomeration factory and Cowper stove process optimization. The system is based on the RT-ARCH real time architecture, an architecture of software tools used in process control. The system is composed of classical algorithms running on a network of PLC-s and controlling algorithms implemented with a process computer. Some of them are typical numerical algorithms, and the others are adaptive control algorithms.