Location-Based Service (LBS) is one of the fundamental and central functionalities of mobile social networks. Since users usually have to report their locations to the LBS providers while using services, the protection of user's location privacy poses a critical challenge. Although many existing approaches can preserve user's location privacy effectively, most of them must include and use the user's real location. In this paper, we first propose an efficient k-anonymity based Dummy Location and divided Circular Area (k-DLCA) approach to protect the user's location privacy. Different from existing studies, the k-DLCA algorithm adopts a greedy strategy to select dummy locations and considers the semantic location information of the location. Moreover, the user's real location may not be contained in the chosen dummy locations. We then show that k-DLCA algorithm can resist the attacks from adversaries, and has a low probability of exposing the user's real location. We conduct extensive simulations to evaluate the efficiency of the proposed scheme. The simulation results demonstrate that our proposed scheme is promising.

Preserving user location and trajectory privacy while using location-based service (LBS) is an important issue. To address this problem, we first construct three kinds of attack models that can expose a user's trajectory or path while the user is sending continuous queries to a LBS server. Then we propose the k- anonymity trajectory (KAT) algorithm, which is suitable for both single query and continuous queries. Different from existing works, the KAT algorithm selects k-1 dummy locations using the sliding widow based k- anonymity mechanism when the user is making single queries and selects k-1 dummy trajectories using the trajectory selection mechanism for continuous queries. We evaluate and validate the effectiveness of our proposed algorithm by conducting simulations for the single and continuous query scenarios.

Network Function Virtualization (NFV) allows multiple Virtual Networks (VNs) to share the underlying physical infrastructure via VN mapping, thus improving the utilization of physical resources. In this paper, for the first time, we study the multicast service-oriented VN mapping that can support big data applications over Elastic Optical Networks (EONs). Since the problem of minimizing the spectrum consumption in multicast service-oriented VN mapping is NP-hard, we propose an efficient heuristic algorithm, called Integrated Genetic and Simulated Annealing (IGSA) algorithm to address the problem with low computational complexity. By encoding node mapping, multicast tree construction, link mapping and spectrum requirements in the same gene and auto-adjusted evolution, and utilizing simulated annealing to find the fittest multicast requests mapping order, IGSA can perform joint optimization for all the multicast requests in a global way. Through extensive simulations, we demonstrate that IGSA outperforms the other heuristic solutions in terms of spectrum consumption, blocking probability and normalized throughput, while achieving close to minimum spectrum consumption with a much lower time complexity than MILP.

One of the challenge issues in network virtualization is the efficient mapping of a virtual network (VN) onto a shared substrate network. The VN mapping problem has been addressed by various researchers. However, these solutions and associated algorithms are only efficient for building unicast service oriented virtual networks, and are not applicable to multicast service oriented VNs. Furthermore, how to guarantee survivability while provisioning a virtual multicast service oriented network is an important issue that has not been addressed. In this work, we investigate the survivable multicast service oriented virtual network provisioning(SMVNP) problem and propose an efficient algorithm with resource sharing for solving this problem. We validate and evaluate our framework and algorithms by conducting simulations on realistic substrate network and by comparing with existing approach. Our simulation results show that our approach outperforms existing solution.

Cloud based datacenters provide on demand services and resources, both transparently and cost effectively. These services and applications are typically hosted and run on the servers located in interconnected datacenters. The task or application request from users can be abstracted as a virtual network (VN) request. How to efficiently accommodate VN requests by mapping them onto the substrate network is a challenging problem. Current research only considers static VN requests, where the VN request and the demand for resources is fixed and does not change over time. However, most of the application requests submitted to datacenters present dynamic changing characteristics. In this paper, we address the issue of how to optimally reconfigure and map an existing VN while this VN request changes. As the VN provisioning problem is NP-hard, we propose heuristic algorithms for solving it efficiently. We evaluate the performance and effectiveness our algorithms by conducting simulations on realistic network. The simulation results show that our approach solves this problem efficiently and performs well than existing approaches.

In the cloud computing paradigm users access applications/services hosted and run on virtual machines in interconnected datacenters. Applications from the same user may need to interact and change data or information, thus, we may abstract the applications/services request from same user as a virtual network (VN). To improve performance and resource efficiency, it is critical that the VN request be optimally provisioned given the current resource state of the datacenters. However, all of the existing research about optimal VN provisioning conducted for deterministic services. In this work, we formulate the problem of optimal provisioning for elastic service oriented VN request as a mixed integer programming (MIP) model with the objective of maximizing the total revenue of infrastructure provider (InP), and propose a genetic algorithm based heuristic (GAH) algorithm for addressing the optimal provisioning for virtual network request with un-splittable flow (OPVNUF) and optimal provisioning for virtual network request with splittable flow (OPVNSF) problems of elastic services. We demonstrate the effectiveness of our approach for improving the total revenue, by conducting extensive simulations on real substrate network.

With the increasingly popular virtualization of both computing and networking resources in a distributed system (called a physical substrate), multiple virtual infrastructures (VIs) can share the physical resources of the underlying substrate, and accordingly even a single failure in the substrate can affect a large number of VIs and the services they offer. Thus, the problem of efficiently mapping a VI to a substrate while guaranteeing the VI's survivability in the event of failures in the substrate becomes important. In this paper, we study the survivable VI mapping problem to protect against link failures in the substrate. We first propose a solution based on traditional shared protection (survivable virtual infrastructure mapping algorithm, P-SVIMA), and then propose a novel VI node migration protection-based algorithm (MP-SVIMA) to minimize the computing and communication resource costs. The MP-SVIMA scheme takes advantage of the flexibility in where VI nodes are mapped in the substrate by migrating a VI node from the originally mapped physical location to a different location after a physical link fails in order to recover from link failures. We compare the efficiency of our solutions using simulations under various performance metrics.

As network virtualization becomes popular, the problem of efficiently mapping a virtual infrastructure (VI) over a substrate network while guaranteeing its survivability in the event of failures becomes increasingly important. In this paper, we study the survivable VI mapping problem to recover from facility node failures. We develop two solutions namely the 1-redundant scheme and the K-redundant scheme for surviving facility node failures while minimizing network resource costs. We also model the two schemes as a MILP problem and propose efficient heuristics based on the MILP formulations. We compare the efficiency of our solutions using simulation under various performance metrics.

As virtualization becomes more and more popular, how to guarantee survivability of a virtual infrastructure (VI) over a wide-area optical network is increasingly important. In this paper, we approach the problem of survivable VI mapping (SVIM) from a few unique perspectives. One of the most distinguishing perspectives is that a large-scale regional failure could destroy one or more facility nodes to which some VI nodes are mapped. Accordingly, redundant facility nodes at different geographical locations and redundant optical connections have to be provisioned such that the VI can still be mapped after the failure. Another distinguishing perspective is that with failure-dependent protection, the SVIM problem can be decomposed into several instances of the basic non-survivable VI mapping (NSVIM) problem, whose solution permits effective sharing of the redundant resources among all failures. In this paper, we first formulate the minimum-cost SVIM problem using mixed integer linear programming (MILP). We then propose an efficient heuristic solution to NSVIM, based on which two novel heuristic SVIM algorithms called Separate Optimization with Unconstrained Mapping (SOUM) and Incremental Optimization with Constrained Mapping (IOCM). Simulations are performed to study and compare the performance of the MILP and heuristics.

Waveband switching (WBS) wherein wavelengths are grouped into bands and switched as a single entity can reduce cost and complexity of switching nodes by minimizing the port count. In this paper, we study the effect of wavelength conversion on the performance of WBS networks with reconfigurable multi-granular optical cross-connects (MG-OXC) to satisfy online traffic. Since wavelength conversion is still expensive and can potentially increase the number of used ports in WBS networks, efficient usage of wavelength converters is of practical interest. We propose a novel heuristic algorithm, called waveband assignment with path-graph (WAPG), which takes efficient wavebanding and efficient usage of wavelength converters into consideration when satisfying new lightpath requests. We apply the WAPG algorithm in WBS networks with full, intra-band, or limited number of wavelength converters, and compare with the FirstFit and RandomFit algorithms. Our results indicate that the proposed algorithm performs significantly better in terms of the blocking probability as well as the number of used wavelength converters.

Constructing wavelength division multiplexing (WDM) multicast switches with inexpensive components and low complexity is an important problem in optical networking, as multicasting is one of the key requirements of emerging bandwidth-intensive applications such as video conferencing, video on demand and online gaming. In this paper we present several new cost-effective designs for constructing nonblocking WDM multicast switching networks. More specifically, we provide a wide-sense nonblocking switch architecture, which uses fewer semiconductor optical amplifiers than existing architectures. In addition, for the first time we have presented a rearrangeably nonblocking WDM switch architecture using array waveguide grating routers and wavelength converters.

Waveband switching (WBS) in conjunction with multigranular optical cross-connect (MG-OXC) architectures can reduce the cost and complexity of switching nodes. In this paper, we study two MG-OXC architectures: the single-layer and the multilayer MG-OXCs, and compare their performances with both off-line (static) and on-line (dynamic) traffic. In the off-line case, a near-optimal integer linear programming models (called off-ILP models) for each of the MG-OXC architectures aims to reduce the size of the MG-OXC, and compares them with the balanced path routing with heavy-traffic first waveband assignment (BPHT) heuristic developed for the multilayer MG-OXCs. The two architectures are then compared in terms of the number of wavelength a fixed number of wavelengths on each link. We also propose a novel efficient heuristic algorithm, called maximum overlap ratio (MOR) to satisfy new requests and compare it with the on-ILP, first-fit, and random-fit algorithms. We compare the two architectures in terms of the blocking probability, weighted (request) acceptance ratio, which serves as an indication of hops (WH) and MG-OXC ports required to satisfy a given set of traffic demands. In the on-line case, we develop an on-line ILP model called on-ILP, which aims to minimize the number of used ports for each of the MG-OXC architectures, given the revenue generated by satisfying the requests. Our results indicate that using WBS with either single-layer or multilayer MG-OXCs can reduce the number of ports (hence the size and cost) of the switching nodes compared to using ordinary OXCs (without waveband switching). In particular, in the off-line case, using single-layer MG-OXCs provides a greater reduction in size than multilayer MG-OXCs, while in the online case, using the multilayer MG-OXC is better.

This paper explores the feasibility of deploying optical burst switching (OBS) in metropolitan area networks (MANs) as an alternative to synchronous optical network (SONET), over wavelength-division multiplexing. We present a comparison between two OBS architectures (with centralized and distributed scheduling schemes), SONET, and next-generation SONET (NG-SONET), respectively. We quantify some of the performance metrics such as end-to-end delay and loss rate when supporting Ethernet traffic in metro ring networks. Our simulation results show that OBS offers significant performance improvement over SONET and NG-SONET. In general, the OBS architecture with distributed scheduling has a superior delay performance, whereas the OBS architecture with centralized scheduling has a better loss metric.

Wavelength band switching (WBS) has only recently attracted attention from the optical networking industry for its practical importance in reducing the control complexity and cost of optical cross-connects (OXCs). However, WBS-related problems of theoretical interest have not been addressed thoroughly by the research community, and many issues are still wide open. In particular, WBS is different from wavelength routing, and thus techniques developed for wavelength-routed networks (including e.g., those for traffic grooming) cannot be directly applied to effectively address WBS-related problems. In this paper, we first propose a new multigranular OXC (MG-OXC) architecture for WBS, which is more flexible than any existing WBS node architectures. We also adopt the most powerful waveband assignment strategy, and develop an efficient heuristic algorithm called Balanced Path routing with Heavy-Traffic first (BPHT). To verify its near-optimality, we also develop an integer linear programming (ILP) model. Both the ILP and the BPHT algorithms can handle the case with multiple fibers per link and hence are more general than our previous single-fiber solutions X. Cao et al. (2002). We conduct a comprehensive evaluation of the benefits of WBS through detailed analysis and simulations. We show that the proposed heuristic BPHT can perform much better than a heuristic which applies the optimal routing and wavelength assignment (RWA) method. We also show that WBS using BPHT is even more beneficial in multifiber networks than in single-fiber networks in terms of reducing the port count. Our analytical and simulation results also provide valuable insights into the effect of wavelength band granularity, as well as the trade-offs between the wavelength-hop and the port count required in WBS networks.

Waveband switching (WBS) has attracted attention from the optical networking industry for its practical importance in reducing port count, the associated control complexity, and cost of optical cross-connects (OXCs). However, WBS-related problems of theoretical interest have not been addressed thoroughly by the research community and many issues are still wide open. In particular, WBS is different from wavelength routing and, thus, techniques developed for wavelength-routed networks (including for example, those for traffic grooming) cannot be directly applied to effectively address WBS-related problems. In this paper, we first develop an integer linear programming (ILP) model, which for a given set of lightpath requests, determines the routes and assigns wavelengths to the lightpaths so as to minimize the number of ports needed. Since the optimal WBS problem of minimizing the port count in WBS networks contains an instance of routing and wavelength assignment (RWA), which is NP-complete, we adopt a powerful waveband assignment strategy and develop an efficient heuristic algorithm called balanced path routing with heavy-traffic first waveband assignment (BPHT). Both the ILP and the heuristic algorithm can handle the case with multiple fibers per link. We conduct a comprehensive evaluation of the benefits of WBS through detailed analysis and simulations. For small networks, our results indicate that the performance of the BPHT heuristic is close to that achievable by using the ILP model and, hence verifying its near-optimality. We show that for larger networks, BPHT can perform better than its variation called balanced traffic routing with maximum-hop first waveband assignment and much better than another heuristic based on optimal (but waveband oblivious) RWA that minimizes wavelength resources. We also show that WBS using BPHT is even more beneficial in multifiber networks than in single-fiber networks in terms of reducing the port count. Our analytical and simulation results provide valuable insights into the effect of wavelength band granularity, as well as the tradeoffs between the wavelength-hop and the port count required in WBS networks.

In wavelength division multiplexed networks (WDM) with 1:1 path protection, a link-disjoint protection (backup) path is also set up at the time of setting up a working (primary) path. Hence, the failure of a single fiber-link does not cause huge data losses. This paper considers on-line routing and wavelength assignment (RWA) of protection paths in such networks. In particular, we study two strategies based on the 1:1 path protection scheme. The static strategy establishes protection paths such that once a route and wavelength have been chosen, they are not allowed to change. On the other hand, the dynamic strategy allows for re-arrangement of protection paths, that is, both the route and wavelength chosen for a protection path can change so as to accommodate a new request. With either strategy, we assume that the working paths cannot be re-arranged. This is to prevent the disruption of on-going traffic. The two strategies are compared on the basis of the number of connection requests that can be satisfied for a given number of wavelengths, assuming that the requests come one at a time, and wavelengths are assigned according to the first-fit policy. One of the results of our study is that, contrary to intuition, the static strategy performs better than the dynamic strategy.