Packet filtering for congestion control under DoS attacks
Congestion control in IP networks is typically done at each router through queue management, and the network is entirely dependent on the end hosts to react congestion. However, when misbehaving flows exist and continue to send their packets in very high rates, the queue management schemes implemented in current IP routers reveal a significant shortcoming in protecting legitimate flows. Here, we propose a novel scheme for congestion control in IP networks. Our approach is a time-window based filtering mechanism implemented in a router and processed before a queue management policy is applied. Setting the window size properly and dropping packets reaching in the next window can catch the nonresponsive nature of misbehaving flows. The performance of our proposed scheme is demonstrated through extensive simulations using the NS2, simulator using a set of simulated traffic generated based on IP traces reported in http://www.nlnar.org.

title: On double-link failure recovery in WDM optical networks
abstract: Network survivability is a crucial requirement in high-speed optical networks. Typical approaches of providing survivability have considered the failure of a single component such as a link or a node. We consider a failure model in which any two links in the network may fail in an arbitrary order. Three loopback methods of recovering from double-link failures are presented. The first two methods require the identification of the failed links, while the third one does not. However, precomputing the backup paths for the third method is more difficult than for the first two. A heuristic algorithm that pre-computes backup paths for links is presented. Numerical results comparing the performance of our algorithm with other approaches suggests that it is possible to achieve 100% recovery from double-link failures with a modest increase in backup capacity.

title: Mobile multi-layered IPsec
abstract: To achieve high throughput in wireless networks, smart forwarding and processing of packets in access routers is critical for overcoming the effects of the wireless links. However, these services cannot be provided if data sessions are protected using end-to-end encryption as with IPsec, because the information needed by these algorithms resides inside the portion of the packet that is encrypted, and can therefore not be used by the access routers. A previously proposed protocol, called Multi-layered IPsec (ML-IPsec) modifies IPsec in a way so that certain portions of the datagram may be exposed to intermediate network elements, enabling these elements to provide performance enhancements. In this paper we extend ML-IPsec to deal with mobility and make it suitable for wireless networks. We define and implement an efficient key distribution protocol to enable fast ML-IPsec session initialization, and two mobility protocols that are compatible with Mobile IP and maintain ML-IPsec sessions. Our measurements show that, depending on the mobility protocol chosen, integrated Mobile IP/ML-IPsec handoffs result in a pause of 53–100 milliseconds, of which only 28–75 milliseconds may be attributed to ML-IPsec. Further, we provide detailed discussion and performance measurements of our MML-IPsec implementation. We find the resulting protocol, when coupled with SNOOP, greatly increases throughput over scenarios using standard TCP over IPsec (165% on average). By profiling the MML-IPsec implementation, we determine the bottleneck to be sending packets over the wireless link. In addition, we propose and implement an extension to MML-IPsec, called dynamic MML-IPsec, in which a flow may switch between plaintext, IPsec and MML-IPsec. Using dynamic MML-IPsec, we can balance the tradeoff between performance and security.

title: Realization of Video Object Plane Decoder on On-Chip Network Architecture
abstract: System-on-chip (SoC) designs provide integrated solutions to challenging design problems in the telecommunications, multimedia, and so on. Present and future SoC are designed using pre-existing components which we call cores. Communication between the cores will become a major bottleneck for system performance as standard hardwired bus-based communication architectures will be inefficient in terms of throughput, latency and power consumption. To solve this problem, a packet switched platform that considers the delay and reliability issues of wires so called Network-on-Chip (NoC) has been proposed. In this paper, we present interconnected network topologies and analyze their performances with a particular application under bandwidth constrains. Then we compare the performances among different ways of mapping the cores onto a Mesh NoC architecture. The comparison between Mesh and Fat-Tree topology is also presented. These evaluations are done by utilizing NS-2, a tool that has been widely used in the computer network design.

title: Throughput Aware Mapping for Network on Chip Design of H.264 Decoder
abstract: Network-on-Chip (NoC) has been proposed as a new methodology for addressing the design challenges of future massly integrated system in nanoscale. In this paper, we present the queuing theory based model for router to evaluate the performance of NoC in terms of drop probability, throughput and energy consumption. Then we apply the linear programming to optimize the allocation of the heterogeneously functional blocks (IPs) onto the given heterogeneous NoC architecture so as to obtain the maximum throughput as well as to optimize the energy dissipation of whole system. Finally, the three differently heterogenous Tree-based network topologies are proposed as the NoC architectures for the study case of H.264 Decoder. This paper also evaluates the proposed topologies by comparing them to other conventional topologies such as 2-D Mesh and Fat-Tree with respects to throughput, power consumption and size. We use the power modelling tool, known as Orion model to calculate the static powers, areas, and dynamic powers of three topologies. The experiment results show that our Tree-based topologies offer similar throughputs as Fat-Tree does and much higher throughputs compared to 2-D Mesh while use less chip areas and energy consumptions.

title: Establishing Pair-Wise Keys in Heterogeneous Sensor Networks
abstract: Many applications that make use of sensor networks require secure communication. Because asymmetric-key solutions are difficult to implement in such a resource-constrained environment, symmetric-key methods coupled with a priori key distribution schemes have been proposed to achieve the goals of data secrecy and integrity. These approaches typically assume that all sensors are similar in terms of capabilities, and hence deploy the same number of keys in all sensors in a network to provide the aforementioned protections. In this paper we demonstrate that a probabilistic unbalanced distribution of keys throughout the network that leverages the existence of a small percentage of more capable sensor nodes can not only provide an equal level of security but also reduce the consequences of node compromise. We demonstrate the effectiveness of this approach on small networks using a variety of trust models and then demonstrate the application of this method to very large systems. The approach and analysis presented in this paper can be applied to all protocols that use probabilistic keys including those that employ broadcast mechanisms, hash functions or polynomials for the generation of keys.

title: Medial axis transform and offset curves by Minkowski Pythagorean hodograph curves
abstract: We present a new approach to medial axis transform and offset curve computation. Our algorithm is based on the domain decomposition scheme which reduces a complicated domain into a union of simple subdomains each of which is very easy to handle. This domain decomposition approach gives rise to the decomposition of the corresponding medial axis transform which is regarded as a geometric graph in the three dimensional Minkowski space R 2,1 . Each simple piece of the domain, called the fundamental domain, corresponds to a space-like curve in R 2,1 . Then using the new spline, called the Minkowski Pythagorean hodograph curve which was recently introduced, we approximate within the desired degree of accuracy the curve part of the medial axis transform with a G 1 cubic spline of Minkowski Pythagorean hodograph. This curve has the property of enabling us to write all offset curves as rational curves. Further, this Minkowski Pythagorean hodograph curve representation together with the domain decomposition lemma makes the trimming process essentially trivial. We give a simple procedure to obtain the trimmed offset curves in terms of the radius function of the MPH curve representing the medial axis transform.