Lemin Li

Path-based routing provisioning with mixed shared protection in WDM mesh networks

In this paper, the authors focus on studying the problem of survivable routing provisioning to prevent single link failure in wavelength-division-multiplexing (WDM) mesh networks, and propose a novel protection scheme called mixed shared path protection (MSPP). With MSPP, the authors define three types of resources: 1) primary resources that can be used by primary paths; 2) spare resources that can be shared by backup paths; and 3) mixed resources that can be shared by both the primary and the backup paths. In the proposed protection scheme, each connection is assigned a primary path and a link disjoint backup path. Differing from pervious protection schemes, MSPP allows some primary paths and backup paths to share the common mixed resources if the corresponding constraints can be satisfied. In this paper, the authors consider three types of path-based protection schemes, i.e., dedicated path protection (DPP), shared path protection (SPP), and MSPP, and evaluate their performance for both the static and the dynamic provisioning problems. Simulation results show that MSPP outperforms DPP and SPP

Dynamic routing and assignment of wavelength algorithms in multifiber wavelength division multiplexing networks

This paper studies multihop optical networks in which nodes employ wavelength routing switches that enable the establishment of wavelength division multiplexed (WDM) channels, called lightpaths, between node pairs. In fact, most optical networks are multifiber networks. The problem of dynamical routing and assignment of wavelength (RAW) in such networks is studied in this paper. Two resource assignment strategies, PACK and SPREAD, are proposed. By virtue of a layered-graph, routing and assignment of wavelength subproblems can be considered simultaneously. These two strategies can be used to solve the RAW problem in networks with even links as well as that in networks with uneven links. Simulation shows that layered-graph-based RAW algorithms perform better than the existing ones. It also shows that SPREAD with distributive use of network resources can achieve better performance than PACK with collective use of resources in multifiber networks. The layered-graph-based algorithms can effectively deal with the failure of the fiber/link and node. By making use of the special structure of the layered-graph, we propose a shortest path algorithm, whose complexity is lower than that of the standard shortest path algorithm.

Shared Sub-Path Protection Algorithm in Traffic-Grooming WDM Mesh Networks

In this paper, we investigate the problem of dynamically establishing dependable connections in wavelength division multiplexing (WDM) mesh networks with traffic-grooming capabilities. We first develop a new wavelength-plane graph (WPG) to represent the current state of the network. We then propose a dynamic shared sub-path protection (SSPP) scheme based on this WPG. To establish a dependable connection, SSPP first searches a primary path for each connection request, and then it segments the found path into several equal-length sub-paths, and computes their corresponding backup paths, respectively. If two sub-paths in SSPP are fiber-disjoint then their backup paths can share backup resources to obtain optimal spare capacity. Based on dynamic traffic with different load, the performance of SSPP has been investigated via simulations. The results show that SSPP can make the tradeoffs between resource utilization and restoration time.

A Novel Survivable Routing Algorithm With Partial Shared-Risk Link Groups (SRLG)-Disjoint Protection Based on Differentiated Reliability Constraints in WDM Optical Mesh Networks

Previous research on survivability with differentiated reliability in wavelength-division-multiplexing (WDM) optical mesh networks mostly considered the failure probability of a fiber link with the link length that may not be a good solution for consideration of shared-risk link groups (SRLGs). In this paper, we propose a new model of failure probability with the SRLG constraints in WDM optical mesh networks. Based on this model, we present the backup resources assignment and the routing selection method with the differentiated reliable requirements of users. To evaluate the performances of this model, we propose a novel survivable routing algorithm called partial SRLG-disjoint protection (PSDP) to tolerate the single-SRLG failure. Compared with the previous algorithm, PSDP can obtain a better resource utilization ratio and lower blocking probability. Simulation results are shown to be promising.

A cost efficient framework and algorithm for embedding dynamic virtual network requests

Cloud computing is a novel paradigm that enables transparent resource sharing over the Internet. With cloud computing users access applications/services and infrastructure resources using thin clients without knowing the actual location or characteristics of the resources. These applications are typically hosted and run on servers in interconnected data centers. The task or application request from the same or different users can be abstracted as virtual network (VN) requests, which are supported by the same underlying substrate network and thus share its resources. Thus, efficient mapping techniques that intelligently use the substrate network resources are important. Current research only considers the case when the VN requests are static. However, user demands and the corresponding VN requests can change dynamically. In this paper, we address the issue of how to optimally reconfigure and map an existing VN while the VN request changes. We first model this problem as a mathematical optimization problem with the objective of minimizing the reconfiguration cost by using mixed integer linear programming. Since the optimal problem is NP-hard we also propose heuristic algorithms for solving it efficiently. We validate and evaluate our framework and algorithms by conducting extensive simulations on different realistic networks under various scenarios, and by comparing with existing approaches. Our simulation results show that our approach outperforms existing solutions.

Dynamic Grooming Algorithms for Survivable WDM Mesh Networks

Within a WDM grooming mesh network and under the constraints of the number of transceivers per node and wavelength continuity, we propose a novel dynamic grooming graph which models the number of transceivers per node in addition to the usage of wavelength and bandwidth resources. Based on the grooming graph, we first propose a dynamic traffic-grooming algorithm called integrated grooming algorithm (IGA). And we also propose two dynamic survivable traffic-grooming algorithms, which are called protection per lightpath traffic-grooming algorithm (PPL) and protection per connection traffic-grooming algorithm (PPC). These algorithms are evaluated via simulations.

On Finding Feasible Solutions With Shared Backup Resources for Surviving Double-Link Failures in Path-Protected WDM Mesh Networks

In this paper, we investigate the problem of dynamic survivable routing in wavelength-division-multiplexing optical networks and propose a new path-protection algorithm called Enhanced Shared Backup Paths Protection (ESBPP) to provide the complete survivability for double-link failures. In order to improve the resource-utilization ratio, we present the new rule of sharing backup resources that can yield better resource-utilization ratio than previous methods. In order to overcome the problem of trap paths, we develop a new routing method to find the feasible solution with three link-disjoint paths for each connection request. Compared to previous algorithms for double-link failures, ESBPP can obtain higher resource-utilization ratio and lower blocking probability

Joint routing-selection algorithm for a shared path with differentiated reliability in survivable wavelength-division-multiplexing mesh networks

A routing-selection algorithm is important in survivable wavelength-division networks. A sound algorithm should carefully consider the efficiency of resource utilization and the protection-switching time. Under shared-risk link group constraints with differentiated reliability (DiR), a novel algorithm for a shared path, called a joint routing-selection algorithm (JRSA) with DiR, is proposed. The simulation results show that a JRSA with DiR not only can efficiently satisfy the specific requirements of users but also can produce nearly optimal performance and determine the appropriatetrade-offs between the resource utilization ratio and the protection-switching time.

Multicast protection scheme in survivable WDM optical networks

The protection design is a key issue in survivable wavelength division multiplexing (WDM) optical networks. Most researches focused on protecting unicast traffic against the failure of a single network component such as a link or a node. In this paper, we investigate the protection scheme for multicast traffic in meshed WDM optical networks under dual-link failure consideration, and propose a novel protection algorithm called shared segment protection with reprovisioning (SSPR). Through dynamically adjusting link-cost according to the current network state, SSPR establishes a primary light-tree and corresponding link-disjoint backup segments for each multicast connection request. A backup segment can efficiently share wavelength capacity of its working tree or the common resource of other backup segments. Capacity reprovisioning establishes new segments for the vulnerable connections after a link failure and tolerates following link failures. The simulation results show that SSPR not only can make good use of wavelength resources and protect multicast sessions against any single-link failure, but also can greatly improve the traffic restorability in the event of dual-link breakdown.

Optimal provisioning for virtual network request in cloud-based data centers

Today applications and services are migrating to a cloud-computing-based paradigm in which the users access the applications and services hosted in data centers, by using thin-clients on the user terminal device. These applications/services are typically hosted and run on virtual machines in interconnected data centers. Different applications from the same user may need to access and change shared data or information. Thus, we may abstract the applications from same user as a virtual network (VN). For better performance and efficiency, it is critical that the VN request be accommodated with optimal provisioning under the current resource state of data centers. In this paper, for addressing the issue of how to design an optimal provisioning scheme for the VN request such that the total revenue of is maximized, we first develop a framework for the optimal provisioning of VN request by using mixed integer programming. Since the optimal provisioning problem is NP-hard, we also propose a genetic algorithm–based heuristic algorithm for addressing the problem of optimal provisioning for VN with unsplittable flow and optimal provisioning for VN with splittable flow problems. We demonstrate the effectiveness of our approach in improving the total revenue by conducting extensive simulations on different networks.