Control framework design is critical to future SDN/NFV-enabled satellite network. However, the current multi-layer constellation based solutions have drawbacks in terms of availability, latency, openness, etc. The key contribution in this work is the study of an efficient control framework, which logically consists of two parts: entity part and overlay part. The entity part is a novel heterogeneous single-layer LEO satellite network, while the overlay part implements a virtualized overlay network. We have implemented a lightweight prototype of our framework and compared it with a GEO satellite based solution (i.e. OpenSAN). We demonstrate proof-of-concept that our framework performs better than OpenSAN with respect to control latency and avoids potential system bottleneck.

Dengue fever has been prevalent for decades in human population and consequently, the human population is partially susceptible to the disease since partial immunity has been gained for those who recovered from dengue infection. We shall obtain an estimation formula for the reproduction number of dengue transmission when the human population is not completely susceptible. This is achieved by taking the number of infected cases periodically notified by surveillance organizations as the solution of a mathematical model for dengue transmission. As an application, the estimation formula is used to estimate the reproduction number of dengue transmission in Singapore in the years 2013 and 2014.

The proposed MSN architecture is intended to directly address the challenge of mobility, which refers to the motion of users as well as the dynamics of the satellite constellation. A virtual access point layer consisting of fixed virtual satellite network attachment points is superimposed over the physical topology in order to hide the mobility of satellites from the mobile endpoints. Then the MSN enhances endpoint mobility by a clean separation of identity and logical network location through an identity-to-location resolution service, and taking full advantage of the user's geographical location information. Moreover, a SDN based implementation is presented to further illustrate the proposal.

In this paper, we propose a rollback traffic avoidance method for the snapshot routing in cyclic mobile networks. Since the snapshot routing tables are switched simultaneously, part of the traffic may be sent back on some links if the new routing path contains the same links but with reversed forwarding direction against the old one. Since the selection of routing paths to avoid the rollback traffic is NP-hard, we propose an approximate algorithm called Inter-Snapshot Rollback Traffic Avoidance (ISRTA), to pursuit the approximate optimal solutions. Evaluation is performed based on the typical cyclic mobile network -- Iridium satellite system, and the simulation results show that our method can efficiently eliminate the rollback paths and traffic in the Iridium system.

In this paper, we propose an offline rollback traffic avoidance method for the snapshot routing in cyclic mobile networks. Since the snapshot routing tables are switched simultaneously, part of the traffic may be sent back on some links if the new routing path contains the same links but with reversed forwarding direction against the old one. To avoid the rollback traffic, we first formulate the rollback traffic avoidance problem as an integer programming problem which is NP-hard, and then we propose an approximate algorithm called Inter-Snapshot Rollback Traffic Avoidance (ISRTA), to pursuit the approximate optimal solutions. Simulation results show that our method can efficiently eliminate the rollback paths and traffic in the Iridium system. Although the global average network delay is increased slightly, the extra end to end delay caused by rollback traffic is eliminated and the packet loss rate is reduced.

In this paper, we propose FlyCast, an architecture using the physical layer of free-space optics (FSO) to accelerate multicast communication. FlyCast leverages off-the-shelf devices (e.g. switchable mirror, beam splitter) to physically split the FSO beam to multi receivers on demand, which enables to build dynamical multicast trees in physical layer and accelerates multicast communications. We demonstrate the feasibility of FlyCast through our theoretical analysis and the proof-of-concept prototype.

We study two discrete predator-prey models in patchy environment, one without dispersal corridors and one with dispersal corridors for the prey. Sufficient conditions to guarantee the permanence of the two predator-prey models are given. By comparing the two permanence criteria, we find that the effects of prey dispersal on the permanence of the predator-prey model are two-fold. Numerical examples are presented to illustrate the effects of the dispersion on the permanence of the predator-prey model.

In recent years, with the rapid development of satellite technology including On Board Processing (OBP) and Inter Satellite Link (ISL), satellite network devices such as space IP routers have been experimentally carried in space. However, there are many difficulties to build a future satellite network with current terrestrial Internet technologies due to the distinguished space features, such as the severely limited resources, remote hardware/software upgrade in space. In this paper, we propose OpenSAN, a novel architecture of software-defined satellite network. By decoupling the data plane and control plane, OpenSAN provides satellite network with high efficiency, fine-grained control, as well as flexibility to support future advanced network technology. Moreover, we also discuss some practical challenges in the deployment of OpenSAN.

This work presents a novel quantum security VoIP phone, called Qphone. Qphone integrates quantum key distribution (QKD) and VoIP steganography, and achieves peer-to-peer communication with information-theoretical security (ITS) guaranteeing. Qphone consists of three parts, a real-time QKD system, RT-QKD, a steganography software, VS-Phone, and an audio encryption and authentication hardware, AE-KEY. RT-QKD explores QKD technologies, and is able establish a shared key between two peers ensuring ITS. VS-Phone utilizes VoIP steganography to protect transmission channels of sensitive information. Qphone can provide efficient and real-time security protections to meet different security demands.

Faster convergence and optimized traffic engineering are always the pursuits of network operators. However, the link state protocols nowadays have obvious inabilities in achieving these network objectives. In link state network, flooding scheme is usually used to spread the state of link connectivity over the network. Generally, link state flooding introduces various timer configurations for tuning convergence performance. The configuration complexity becomes the major reason of protocol inability to optimize routing convergence. On the other hand, traffic engineering is poorly supported by link state protocol because of temporary status which may cause unexpected traffic migration and packets loss. In this paper, we propose a routing model through which the link state information is disseminated in a globally controllable way. Our model removes existing limitations for accelerating convergence. Meanwhile, our model can integrate traffic engineering into link state protocol by disseminating optimized link weight, thus avoiding the inefficiencies of massive network configurations. Our experiments show that our model can achieve better convergence time and significantly reduce overhead. At the same time, our model is fully scalable with network size. We believe that our model can enhance network convergence and traffic engineering performance simultaneously, as well as prevent unexpected network transitions to improve network reliability.

In the challenged networks, such as interplanetary networks, satellite networks, military networks and so on, a complete path from the source to the destination does not exist for most of the time. The lack of end-to-end path makes the message delivery a great challenge in these networks. In this paper, we propose the spray and routing message delivery mechanism, which combines the simplicity of epidemic routing and the efficiency of direct routing. We evaluate the performance of Spray and Routing via simulation using the ONE simulator, in comparison with the traditional Epidemic, Prophet and Spray and Waiting protocols. The simulation results show that our method can achieve better performance.

With the rapid development of various types of space applications, space information network faces more and more challenges about the quality of service. How to provide end-to-end QoS based on the limited resources of space information network becomes one of the research focuses. In this paper, a method of dynamic deprivable bandwidth allocation (DDBA) is proposed for delay-sensitive specific applications. Applications are classified to three service levels according to the sensitivity of the delay. High level of services can deprive the bandwidth which has been allocated to the low level of services under certain situation. The results of the simulation illustrate that DDBA improves the use efficiency of the limited bandwidth compared to those typical bandwidth allocation algorithms. Furthermore, the DDBA can also reduce the delay of high level DS services and depress the lost rate.

Both IP multicast and application layer multicast (ALM) are always using tree structure as data delivery path, but the adaptiveness to the dynamic behaviors of member nodes in ALM trees is weaker than that of IP multicast trees. In ALM tree, when a parent node leaves or fails, all its descendent nodes must adjust their positions in the ALM tree, which causes the interruption of multicast data transmission seriously. This phenomenon is called stability problem of ALM trees. Firstly, this paper analyzes the stability problem of ALM trees and proposes the instantaneous stability degree model (ISDM). Secondly, an approach that takes advantage of the statistical properties of memberpsilas join-leave behaviors is proposed to estimate the Leave Probabilities of member nodes for the model. Thirdly, the various factors related to the instantaneous stability of ALM trees are analyzed through simulations. The modeling and analyzing the instantaneous stability of ALM trees have established a theoretical basis for constructing stable ALM trees, and therefore some possible directions for the future work are discussed finally.

Recently, application layer multicast (ALM) has become an effective alternative to IP multicast across the Internet. By deeply analyzing the characteristics of traditional packet forwarding in end host, this paper proposes a high performance multicast scheme, in which a NIC-based multicast mechanism is used to send multiple replicas of a ALM packet to different destinations with less CPU intermediation compared to the traditional host- based multicast scheme. By adopting the NIC-based multicast scheme, the CPU overhead and the number of times data packets are copied from host memory to NIC buffer are reduced. Theoretical analysis indicates that the new scheme can notably decrease the multicast delay and enhance the service capability of ALM proxies. We have modified the NIC driver and added some corresponding APIs to network protocol stack in order to implement the proposed scheme. Experimental results illustrate that the NIC-based multicast scheme can greatly improve forwarding rate for ALM.