Egress Nodes Research Articles

IFTS: A Location Privacy Protection Method Based on Initial and Final Trajectory Segments

Privacy protection problem is one of the most concerning issues related to Location-Based Services (LBS) in our daily life. Privacy protection of LBS often requires anonymizing customer's trajectory data. Currently available methods for trajectory anonymity often assume an entire trajectory as one anonymous unit, which may lead to low anonymity efficiency due to the massive amount of trajectory data, especially for customers travel through a long road. Considering people's routine activities, the starting and ending locations of a trip often uncover the user's request intent, which may lead to exposure of user privacy. In order to address the problem of inefficient trajectory anonymity, we propose a location privacy protection method that is based on the initial and final trajectory segmentation (IFTS) in this paper. In the IFTS method, the road network structure is first transformed into an edge cluster model based on its location type. Then, the user trajectory is divided to segments according to the temporal sequence of the ingress and egress nodes. The initial and final trajectory segments are identified and divided into equivalence classes, which then are used for constructing a trajectory graph and the corresponding k-anonymous set. Our experimental results show that the proposed method can reduce the anonymous area, improve anonymity efficiency, and enhance trajectory data utilization compared to the existing methods for trajectory anonymity.

Design of Emergency Evacuation Scheme for Louvre

In this paper, we used four steps in analyzing the optimal model of evacuation within the Louvre. For step 1, we refer to the traffic concept in the Dynamic Network Flow Model to define the export throughput. For step 2, considering that the original floor plan is segmented with pixel points as a unit with high complexity and little meaning, we simplify the floor plan when the model is guaranteed to be true. For step 3, we first mark the exit node, make its dual graph, and draw the point chain containing the exit node, which can divide the original image into several pieces according to the area. Breadth-First Search from each egress node can mark themselves with color, ownership and other information. For Step 4, in order to get the optimal segmentation which satisfies the definition of reasonable segmentation edge set, we use Genetic Algorithm to solve the optimization problem. A sequence consisting of the sequence numbers in the set of Edge-Cut is encoded as a gene in the Genetic Algorithm and iterated by the Theory of Chromosome Cross-Variation to obtain an optimal solution. Finally, we have designed a scientific and complete emergency evacuation plan.

Flow termination signaling in the centralized pre-congestion notification architecture

Pre-congestion notification (PCN) protects inelastic traffic by using feedback on network link loads on and acting upon this accordingly. These actions comprise to admission control and termination of flows. Two PCN architectures have been defined by IETF: the centralized and decentralized PCN architecture. The decentralized PCN architecture has received much attention in the literature whereas the centralized PCN architecture has not. In the decentralized architecture, feedback is sent from the egress nodes to ingress nodes, which then take and apply decisions regarding admission of new flows and/or termination of ongoing flows. Signaling occurs only between ingress and egress nodes.In the centralized architecture these decisions are made at a central node, which requires proper signaling for action and information exchange between the central node and the egress and ingress nodes. This signaling has been suggested by other authors, but is not fully defined yet. Our contribution is twofold. We define signaling in the centralized PCN architecture focussing on flow termination, which completes the definition of the signaling in the centralized PCN architecture. Secondly, we run extensive simulations showing that the proposed signaling works well and that the performances of the centralized PCN and the decentralized PCN architectures are similar. Hence, it is expected that results from existing research on the effectiveness of decentralized PCN are also valid when the centralized PCN architecture is used.

Emergency navigation without an infrastructure.

Emergency navigation systems for buildings and other built environments, such as sport arenas or shopping centres, typically rely on simple sensor networks to detect emergencies and, then, provide automatic signs to direct the evacuees. The major drawbacks of such static wireless sensor network (WSN)-based emergency navigation systems are the very limited computing capacity, which makes adaptivity very difficult, and the restricted battery power, due to the low cost of sensor nodes for unattended operation. If static wireless sensor networks and cloud-computing can be integrated, then intensive computations that are needed to determine optimal evacuation routes in the presence of time-varying hazards can be offloaded to the cloud, but the disadvantages of limited battery life-time at the client side, as well as the high likelihood of system malfunction during an emergency still remain. By making use of the powerful sensing ability of smart phones, which are increasingly ubiquitous, this paper presents a cloud-enabled indoor emergency navigation framework to direct evacuees in a coordinated fashion and to improve the reliability and resilience for both communication and localization. By combining social potential fields (SPF) and a cognitive packet network (CPN)-based algorithm, evacuees are guided to exits in dynamic loose clusters. Rather than relying on a conventional telecommunications infrastructure, we suggest an ad hoc cognitive packet network (AHCPN)-based protocol to adaptively search optimal communication routes between portable devices and the network egress nodes that provide access to cloud servers, in a manner that spares the remaining battery power of smart phones and minimizes the time latency. Experimental results through detailed simulations indicate that smart human motion and smart network management can increase the survival rate of evacuees and reduce the number of drained smart phones in an evacuation process.

A load balancing multi-path routing scheme based on effective voids for optical burst switching networks

Multi-path routing in the optical burst switching (OBS) networks can reduce the burst loss probability (BLP) by distributing the data burst traffic to multiple paths, compared with single path routing. Unlike the other multi-path routing schemes without considering the carrying capability of the routes, a new multi-path routing scheme based on effective voids (MPEV) is proposed to balance the load of multi-path and reduce the BLP in the paper. MPEV scheme first obtains the information on effective voids of the bottleneck link of multipath by sending a probe packet periodically. The effective voids can accommodate data bursts and accurately represent the available channel resource that is the main determinant of the BLP for OBS networks without optical random access memory. Then MPEV scheme distributes the burst traffic between an ingress node and an egress node to multiple link-disjoint paths by the ratio of the effective voids. More traffic is distributed to the path that has more effective voids, and vice versa. And the distributed amount is proportional to the effective voids of the bottleneck link. So MPEV scheme can balance the load of multi-path routes and can effectively reduce the BLP by avoiding the high load of a single path. And it is easy to implement and agilely adapt to dynamic network traffic. The performance of MPEV scheme is analyzed by queuing theory and is evaluated by simulation. The numerical results show that the proposed scheme can effectively reduce the BLP and balance the traffic load over multiple paths at the same time.

Label switched protocol routing with guaranteed bandwidth and end to end path delay in MPLS networks

Rapid growth of multimedia applications has caused a tremendous impact on how people communicate. Next generation networks (NGN) have been proposed to support newly emerged multimedia IP based applications such as voice over IP (VOIP), video on-demand (VOD), and IPTV using a core IP backbone. The development of technologies like Multi-Protocol Label Switching (MPLS) has laid the foundation for NGN to support multimedia applications like Voice over IP. One of the important concepts in MPLS Traffic Engineering (TE) is Label Switched Path (LSP) routing. The objective of the routing algorithm is to increase the number of accepted request while satisfying Quality of Service (QoS) constraints. Although much work has been done on laying MPLS paths to optimize performance, most of them have focused on satisfying bandwidth requirements. Relatively little research has been done on laying paths with both bandwidth and delay constraints. In this paper, we present a new bandwidth and end to end delay (bandwidth-delay) constrained routing algorithm which uses data of the ingress–egress node pairs in the network. In this algorithm we use LR-Servers theory to compute path delay. We name the proposed algorithm as Minimum Delay and Maximum Flow (MDMF). We do extensive simulations to evaluate the performance of MDMF algorithm. In addition, we compare the performance of MDMF against some previous related works such as MHA, WSP, MIRA, BCRA, MIRAD, BGDG, BGLC, and SAMCRA. The simulation results show that MDMF rivals them in terms of flow management and outperform them in terms of end to end delay management, maximum flow and number of accepted request (call blocking ratio).

Load balancing Technique for VOIP in MPLS Networks

In recent years, there has been a phenomenal growth in the commercial deployment of delay-sensitive services, such as voice and video services, over the Internet Protocol. Regardless of the advances that have been witnessed in networking technologies, effectively utilizing the network resources to accommodate such services remains a major and challenging task for network researchers and designers. In MPLS networks, multiple label switched paths are (LSP) are established between MPLS ingress and egress nodes to enhance the network performance and QoS for subscribers. During unbalanced situation in the network, the flows are routed through multiple paths. Keywords- MPLS, load balancing, , VoIP and QoS, broadband scenario, Voice, multipath dispersion, , IP network.

Establishment of Dynamic Lightpaths in Filterless Optical Networks

In this paper, we study the performance of dynamic routing and wavelength assignment (RWA) in filterless optical networks. These types of broadcast and select networks benefit from breakthroughs in advanced transmission technologies for replacing optical filters and active photonic switching devices, such as wavelength selective switches, with passive optical interconnections between nodes, creating passive optical light trees. We introduce an RWA scheme for establishing passive optical lightpaths in a filterless context and managing unfiltered channels at intermediate egress nodes, which, by propagating downstream of the terminating nodes, participate in wavelength usage and increase the risk of wavelength exhaustion. Simulation results are presented for six network topologies, along with the performance evaluation of active photonic and filterless optical network solutions with static and dynamic RWA schemes. We show that the performance of the proposed scheme depends on the average degree of node connectivity.

Path diversification for future internet end-to-end resilience and survivability

Path Diversification is a new mechanism that can be used to select multiple paths between a given ingress and egress node pair using a quantified diversity measure to achieve maximum flow reliability. The path diversification mechanism is targeted at the end-to-end layer, but can be applied at any level for which a path discovery service is available. Path diversification also takes into account service requirements for low-latency or maximal reliability in selecting appropriate paths. Using this mechanism will allow future internetworking architectures to exploit naturally rich physical topologies to a far greater extent than is possible with shortest-path routing or equal-cost load balancing. We describe the path diversity metric and its application at various aggregation levels, and apply the path diversification process to 13 real-world network graphs as well as 4 synthetic topologies to asses the gain in flow reliability. Based on the analysis of flow reliability across a range of networks, we then extend our path diversity metric to create a composite compensated total graph diversity metric that is representative of a particular topology's survivability with respect to distributed simultaneous link and node failures. We tune the accuracy of this metric having simulated the performance of each topology under a range of failure severities, and present the results. The topologies used are from national-scale backbone networks with a variety of characteristics, which we characterize using standard graph-theoretic metrics. The end result is a compensated total graph diversity metric that accurately predicts the survivability of a given network topology.

Evaluating the Burst Delivery Ratio of TCP Variants with Varying Burst Sizes and Offset Times in an all-Optical Burst Switching Network

o protract next generation Internet, TCP over OBS is a potential transport paradigm. Since the popular variants of TCP were designed to work with IP networks, they behave differently over OBS networks. Packets from various IP sources assemble into a Data burst and it is transmitted from ingress node to egress node cutting through the core nodes all- optically. Data burst is always preceded by a control packet with an offset time. Owing to bufferless nature of OBS burst losses may occur due random contention. In this scenario an experimental study was made to evaluate the performance of two popular TCP variants, TCP-Reno and TCP-Vegas using NS-2. KeywordsControl Protocol (TCP), Internet protocol (IP), Optical Burst Switching (OBS) Network, TCP-Reno, TCP- Vegas, Network Simulator version-2 (NS-2)

Path correlation considered prioritized burst segmentation for quality of service support in optical burst switching networks

Burst segmentation (BS) is a high-efficiency contention resolution scheme in bufferless optical burst switching (OBS) networks. A prioritized BS scheme for quality of service (QoS) support is developed. Unlike the existing work on the BS scheme, the proposed BS model considers path-correlated factors, such as path length, the adjoining paths carrying traffic on a given path, and the multipriority traffic coming from all paths. Byte loss probability for high-priority and low-priority bursts under the time-based assembly approach and the length-based assembly approach to estimate the performance of the proposed BS scheme by comparing the cumulative distribution function of a burst length in an OBS ingress node (source) with that in an egress node (destination) is introduced. A preemptive BS policy for different priority bursts is proposed to support the QoS of the OBS network. Finally, a simulation is given to validate the proposed analytical model in an existing OBS network with two priority bursts. It is shown that the proposed BS scheme can realize the service differentiation for multipriority traffic under the consideration of network topology-dependent parameters.

RCFT: A Termination Method for Simple PCN-Based Flow Control

Pre-congestion notification (PCN) conveys information about load conditions in differentiated services IP networks to boundary nodes. This information is currently used for admission control and flow termination. Flow termination complements admission control, e.g., in case of failures when admitted traffic is rerouted and causes overload on backup paths. Existing approaches for PCN-based admission control and flow termination operate on ingress-egress aggregates and rely on a signalling protocol that regularly reports measured PCN feedback from all egress nodes to all ingress nodes. However, this signalling protocol is neither defined nor available, and the methods have also other intrinsic shortcomings that result from their operations on ingress-egress aggregates. While there is already a PCN-based admission control method that works without additional signalling of measured PCN feedback, a solid flow termination method with that property is still missing. In this paper we present the novel regular-check-based flow termination method (RCFT). It does not rely on measured PCN feedback, fills the identified gap, and allows for a PCN architecture without signalling of measured feedback. We explain RCFT in detail and investigate its termination behavior under various conditions. Moreover, we study the use of PCN-based flow control for on/off traffic. These results are of general nature and apply to any system using PCN-based flow termination.

Multipath Adaptive Packet Dispersion for Voice Applications

Problem statement: The quality of Voice over IP applications is decided by the main factors like network capacity and technologies such as codec type, Packet Loss Concealment (PLC) and Forward Error Correction (FEC). Approach: In MPLS networks multiple Label Switched Paths (LSP) are established between MPLS ingress and egress nodes to enhance the network performance and QoS for subscribers. To enhance the Quality of Service, Multipath adaptive packet dispersion is proposed for voice applications in IP networks. Results: The trigger handler is proposed to check the balanced load in the system. If the network condition becomes unbalanced, the adaptive packet scheduler classifies the flows and routed to the best shortest paths with the help of proposed packet dispersion technique. Conclusion: The VoIP traffic is routed along the most adequate path that has enough resource to meet a given target QoS. Simulation results are reported to show the efficiency of the proposed technique for effective VOIP flows.

Performance of PCN-Based Admission Control Under Challenging Conditions

Precongestion notification (PCN) is a packet-marking technique for IP networks to notify egress nodes of a so-called PCN domain whether the traffic rate on some links exceeds certain configurable bounds. This feedback is used by decision points for admission control (AC) to block new flows when the traffic load is already high. PCN-based AC is simpler than other AC methods because interior routers do not need to keep per-flow states. Therefore, it is currently being standardized by the IETF. We discuss various realization options and analyze their performance in the presence of flash crowds or with multipath routing by means of simulation and mathematical modeling. Such situations can be aggravated by insufficient flow aggregation, long round-trip times, on/off traffic, delayed media, inappropriate marker configuration, and smoothed feedback.

Edge router selection and traffic engineering in LISP-capable networks

Recently, one of the problems with the Internet is the is- sue of scalability. To this end, locator/identifier separation protocol (LISP), which separates end-system identifiers and routing locators, has been proposed as a solution. In the LISP deployed network, the ingress and egress nodes of inter-AS traffic is determined by edge router selection (ERS) and endpoint identifier-routing locator mapping assignment (ERMA). In this paper, joint optimizations of ERS and ERMA for stub networks with and without pre- determined link weights are studied and the mixed integer linear programming (MILP) formulations for the problems are given. To make the problem with optimizable link weights tractable, a re- vised local search algorithm is also proposed. Simulation results show that joint optimization of ERS and ERMA enables better net- work performance.

Analysis of Burst Segmentation in Optical Burst Switching Networks Considering Path Correlation

One of the key problems hindering the realization of optical burst switching (OBS) technology in the core networks is the losses due to contention among the bursts at the core nodes. Such contention losses do not necessarily indicate a situation of congestion. Burst segmentation is an effective contention resolution technique used to reduce the number of packets lost due to the burst losses. In this work, we propose a method of analyzing the benefit of burst segmentation considering the effect of correlation in traffic across multiple paths. Starting with the cumulative distribution function (cdf) of the length of the bursts at the ingress node destined to a particular egress node, we evaluate the cdf of the burst length at each node along the path considering the probability of segmentation and the traffic on the adjoining paths. Comparing the burst length at the egress node with that at the ingress node, we evaluate the byte loss probability (ByLP) along the path and also the network-wide average ByLP. The proposed analytical framework studies the impact of segmentation on packet loss rate considering the effect of the length of a path, the number of paths adjoining a path (extent of path correlation), the effect of load on a path and other correlated paths, and the burst assembly algorithm. Analytical and simulation results in this work show that the proposed method of analysis gives a good understanding of the influence of aforementioned factors on the benefit of segmentation in OBS networks.

Employing Code Domain for Contention Resolution in Optical Burst Switched Networks With Detailed Performance Analysis

We propose the implementation of spectral-amplitude-coding optical code division multiple access (SAC-OCDMA) as a contention resolution technique in optical burst switched (OBS) networks. The new system architecture is presented in details where an all-optical methodology for cancelling multiple access interference is proposed. Performance evaluation of the proposed system in both MAC and optical layers is introduced where the overall burst error rate of the system is evaluated in three cases: full, partial, and no code conversion capabilities taking into account the receiver dark current, thermal, and shot noises at the egress nodes. Our results reveal that a considerable improvement in the performance of each core node in the system is achieved by using SAC-OCDMA instead of WDM in the optical layer underneath an OBS based MAC layer. We also conclude that a slight increase in the employed number of code converters enhances the overall system performance noticeably. Finally, optimum values for the number of codes, which lead to minimum overall burst error rate, are reached at different traffic conditions.

Improvement Of Link Failure Restoration Utilising Multi-Protocol Label Switching (Mpls) As A Means To Maintain Quality Of Service (QOS)

Stable Food Crops Turning Into Commercial Crops: Case studies of Teff, Wheat and Rice in Ethiopia This paper proposes a practical approach to the enhancement of Quality of Service (QoS) routing by means of providing alternative or repair paths in the event of a breakage of a working path. The proposed scheme guarantees that every Protected Node (PN) is connected to a multi-repair path such that no further failure or breakage of single or double repair paths can cause any simultaneous loss of connectivity between an ingress node and an egress node. Links to be protected in an MPLS network are predefined and a Label Switched path (LSP) request involves the establishment of a working path. The use of multi-protection paths permits the formation of numerous protection paths allowing greater flexibility. Our analysis examined several methods including single, double and multi-repair routes and the prioritization of signals along the protected paths to improve the Quality of Service (QoS), throughput, reduce the cost of the protection path placement, delay, congestion and collision. Results obtained indicated that creating multi-repair paths and prioritizing packets reduces delay and increases throughput in which case the delays at the ingress/egress LSPs were low compared to when the signals had not been classified. Therefore the proposed scheme provided a means to improve the QoS in path restoration in MPLS using available network resources. Prioritizing the packets in the data plane has revealed that the amount of traffic transmitted using a medium and low priority Label Switch Paths (LSPs) does not have any impact on the explicit rate of the high priority LSP in which case the problem of a knock-on effect is eliminated.

Minimizing transceivers in optical path networks

The problem of routing traffic on multihop clear optical channels and deciding the virtual topology of optical channels to form on a physical network of fibers to minimize the cost of electronic switching equipment has become known as traffic grooming in optical networks. Traffic grooming is recognized as an important research area, because the joint opto-electric routing problem is a hard one, yet necessary because of the large cost of pure electronic switching. This problem has been shown to be NP-complete (nondeterminstic polynomial complete) even for very simple practical topologies such as a path network. In previous work, we have shown that at least the subproblem of routing traffic on a given virtual topology to minimize electronic switching (NP-hard for path networks with arbitrary traffic matrices) becomes polynomial when the traffic on the path is restricted to be egress traffic, that is, all traffic requests are destined for a single egress node. In that work, the objective was to minimize the raw OEO (opto-electro-optic) metric (number of bits electronically switched per second) totaled over all network nodes. Of late, it has become clear that electronic switching equipment cost is best counted in quantized units, e.g., in the number of transceiver interfaces at network nodes. In this paper, we consider the traffic grooming problem in unidirectional, WDM path networks with the goal of minimizing the number of transceivers. We conclusively show that the problem is NP-hard, even under the restriction of the egress traffic model. In the case of egress traffic, we give a simple heuristic that will never be worse than twice the optimal.

Threshold configuration and routing optimization for PCN-based resilient admission control

Pre-Congestion Notification (PCN) in IP networks uses packet metering and marking within a PCN domain to notify its egress nodes whether link-specific admissible or supportable rate thresholds have been exceeded by high-priority traffic. Based on this information simple admission control and flow termination is implemented. The latter is a new flow control function and useful in case of overload through high priority traffic which can occur in spite of admission control, e.g., when traffic is rerouted in failure cases. Resilient admission control admits only so much traffic that admitted traffic can be rerouted without causing congestion on backup paths in case of a likely failures, e.g., single link failures. We propose algorithms to configure the link-specific PCN rate thresholds such that resources are utilized efficiently and fairly by competing traffic aggregates while meeting resilience constraints. This is done for the single and dual marking PCN architecture whereby the single marking case is more demanding since it requires that the supportable rate is a fixed multiple of the admissible rate on all links within a single PCN domain. Furthermore, we derive objective functions to optimize the underlying routing system for both cases. Our performance results for various network types show that the dual marking PCN architecture leads to significantly better resource efficiency than the single marking PCN architecture.