Survivability in multi-domain optical networks using p-cycles

Survivability is becoming an important issue in optical networks due to the huge bandwidth offered by optical technology. Many works have studied network survivability. The majority of these works are destined for single-domain networks. In this work, we address the survivability of multi-domain optical networks. This paper provides a classification of the existing protection solutions proposed for multi-domain networks and analyses their advantages and limitations. We propose a new solution for multi-domain optical networks based on p-cycles (pre-configured cycles). For scalability and security reasons, we also propose a topology aggregation model adapted to p-cycle computations. This aggregation model allows our proposed solution to find a trade-off between two competing goals: efficient use of backup resources and short running time. Simulation results show that the proposed solution is a good trade-off between resource utilization and running time compared to existing solutions.     

Applying PTF/VTF routing policies in multilayer IP/MPLS-based ASON/GMPLS multi-domain networks

The IP/MPLS-based ASON/GMPLS hybrid network architecture enables the interaction between the IP layer and the optical dense wavelength division multiplexing (DWDM) layer. This architecture makes it possible to transfer huge amounts of traffic data on DWDM networks, while supporting Internet Protocol (IP)-based service applications. Additionally, this architecture provides a unified routing scenario, which allows the dynamic routing in both the IP layer and/or optical layer. Cross- layer routing has been addressed in single domain networks scenarios, where the routing policies Physical Topology First (PTF) and Virtual Topology First (VTP) have been proposed and applied. However, applying cross-layer routing using both routing topology policies PTF and VTF has not been investigated in a multi-domain networks scenario yet. In this study, we address this issue and propose a routing scheme to establish traffic connections in the optical WDM layer and the IP layer, which makes the applicability of PTF and VTF in multilayer multi-domain network feasible.     

A novel domain-by-domain survivable mechanism in multi-domain wavelength-division-multiplexing optical networks

In multi-domain wavelength-division-multiplexing (WDM) optical networks, the inter-domain routing is a challenge since each single-domain cannot view the full network topology. At the same time, survivability is also an important issue in optical networks since the failures of fiber links or network nodes may lead to a lot of traffic being blocked. In this paper, we study the survivability in multi-domain WDM optical networks, and propose a new survivable mechanism called load balanced domain-by-domain routing (LBDDR). In LBDDR, in order to obtain the efficient inter-domain survivable routes, we present the domain-by-domain routing (DDR) method which can find the intra-domain sub-working path and sub-backup path in each single-domain to form the inter-domain working path and backup path for each demand. In order to reduce the blocking probability, we present the load balanced routing method which can encourage the traffic to be uniformly distributed on the links with more free wavelengths. Simulation results show that, compared with conventional mechanism, LBDDR can obtain better performances.     

多域光网络中一种支持区分可靠性的通路保护算法

区分可靠性的通路保护方案既能为光网络中具有不同可靠性需求的业务提供有效的故障保护,又能优化网络资源的利用,是一种高效的生存性机制。但目前此类问题的研究主要是集中于传统的单域光网络中,所得的研究成果无法直接运用于具有多域特点的下一代光网络中。针对这一问题,在对以往通路保护算法进行改进的基础上提出了一种适用于多域光网络中的支持区分可靠性的通路保护算法,并对其性能进行了计算机仿真研究。仿真结果表明,该算法不仅能满足多域光网络中不同业务的可靠性需求,而且能提高网络资源的利用率、降低业务连接的阻塞率。     

认知网络中的一种多域本地认知方法

During the evolution from cognitive radio to cognitive networks, the environment cognition extended from wireless environments to network and user environments. To understand the basic theory of Local Mul-ti-Domain Cognition (LMDC), and to provide a theoretical basis for further study in cooper-ative multi-domain cognition and initiative multi-domain cognition, the LMDC is inves-tigated in this paper. A Local Single-Domain Cognitive (LSDC) approach is first proposed based on multidimensional edge detection theory. This approach can divide the parameter space that describes the single-domain environment into different areas, and can represent each area with an identifier. Using this as a foundation, the single-domain environment is extended to multi-domain environments, and an LMDC approach is presented to describe the LMDC environment. The paper concludes by introducing two examples and the corre-sponding analysis to illustrate the feasibility of the proposed LMDC approach.     

Inter group shared protection (I-GSP) for survivable WDM mesh networks

This paper focuses on the survivable routing problem in WDM mesh networks where the objective is to minimize the total number of wavelengths used for establishing working and protection paths in the WDM networks. The past studies for survivable routing suffers from the scalability problem when the number of nodes/links or connection requests grows in the network. In this paper, a novel path-based shared protection framework, namely inter group shared protection (I-GSP), is proposed where the traffic matrix can be divided into multiple protection groups (PGs) based on specific grouping policy. Optimization is performed on these PGs such that sharing of protection wavelengths is considered not only inside a PG, but between the PGs. Simulation results show that I-GSP based integer linear programming model, namely, ILP-II solves the networks in a reasonable amount of time for which a regular integer linear programming formulation, namely, ILP-I becomes computationally intractable. For most of the cases the gap between the optimal solution and the ILP-II stays within 6%. The proposed ILP-II model yields a scalable solution for the capacity planning in the survivable optical networks based on the proposed I-GSP protection architecture.     

多域光网络联合路由保护算法

研究了多域光网络中的路由保护问题。为了避免多域光网络通路保护二步算法可能导致的多域陷阱问题,提出了一种基于Suurballe算法扩展的多域联合路由保护算法。仿真表明,相比传统的多域通路保护二步算法,该算法资源利用率高,阻塞率低,平均每连接跨域数小。     

A novel method to evaluate clustering algorithms for hierarchical optical networks

The routing issues in multi-layer and multi-domain optical networks have drawn much attention in current research. With the introduction of the path computation element, routes can be calculated more efficiently in multi-domain optical networks. However, the optimal degree of routing approach in multi-layer and multi-domain optical networks is also determined by the clustering algorithms deployed for construction of hierarchical networks. Therefore, it is important to investigate the way to evaluate the impact of the clustering algorithm on the routing approach (e.g., blocking probability) in optical networks with dynamic traffic, which has not been studied sufficiently. In this paper, a novel method to describe and evaluate the clustered structures generated by different clustering algorithms for hierarchical optical networks is proposed. This method deploys a novel evaluation metric that represents blocking probability of clustered optical networks, so it can be used as guidelines for designing clustered structures. Besides theoretical analysis, simulations are carried out on different network topologies and clustered types to validate the effectiveness of the method presented.     

Hierarchical routing and traffic grooming in IP/MPLS-based ASON/GMPLS multi-domain networks

Routing, connection setup, and path computation are well-known problems in multi-domain networks, which have been largely analyzed in pure IP (packet) networks. In circuit-switched optical multi-domain networks, there remain, however, a number of routing and path computation challenges. Traffic grooming means combining a number of low-speed traffic streams so that the high capacity of each lightpath may be used as efficiently as possible, as path computation implements the core of the grooming function, it is obvious that solutions for the traffic grooming problem in optical multi-domain networks are still not sufficiently investigated. In this study we propose a methodology to address the problems of routing, connection setup, and traffic grooming in optical multi-domain networks, which adapts a two-level hierarchical routing scheme and full-mesh topology abstraction algorithm to improve routing scalability and lower inter-domain blocking probabilities; additionally our proposed methodology adapts a scheme for traffic grooming in DWDM multi-domain networks to improve the resources usage. To test our proposed methodology we propose a detailed IP/MPLS-based ASON/GMPLS multi-domain multilayer test framework.     

Multi-domain architecture for policy management inumts ip multimedia subsystem

The Universal Mobile Telecommunications System (UMTS) offers IP-based multimedia applications and services with end-to-end Quality of Service (QoS) guarantee. The key component providing these services is the IP Multimedia Subsystem (IMS) that uses Service-Based Local Policy (SBLP) management for QoS control. To support end-to-end QoS, the UMTS IMS network should be scalable, reliable and flexible in policy deployment and enforcement, characteristics that are not found in single-domain policy architecture. A hybrid policy architecture is proposed, in which a hierarchical architecture is applied to the multi-domain environment in a single operator UMTS IMS network, while a peering architecture is employed in a multi-operator UMTS IMS network. The proposed multi-domain policy architecture potentially minimizes the session setup delay and policy exchange traffic while maximizing network scalability.     

Waveband Grooming based on Layered Auxiliary Graph in multi-domain optical networks

With the number of wavelengths on fibers keeps increasing, the size and the cost of Optical Cross-Connect (OXC) are greatly enhanced and then the control and management of optical switches become more and more complicated. Therefore, the technique called waveband switching is proposed to reduce the size and the cost of OXC; that is, to save the All-Optical (OOO) switching ports in OXC. However, the existing waveband switching algorithms are all limited in single-domain optical networks. Actually, with the scale of optical backbone keeps enlarging, the network is divided to multiple independent domains to perform the hierarchy routing for achieving the scalability. In order to reduce the size and the cost of OXC meanwhile to achieve the scalability in multi-domains, in this paper we propose a new heuristic algorithm called Waveband Grooming with Layered Auxiliary Graph (WGLAG) since the waveband grooming problem is the NP-hard to perform the inter-domain routing based on the virtual topology of multi-domain network and the intra-domain routing based on the physical topology of single-domain network. In intra-domain routing with waveband grooming of each single-domain, we propose the Layered Auxiliary Graph (LAG) that includes one virtual topology layer and multiple waveband-plane layers to compute a single-hop, or multi-hop or hybrid waveband route for each connection request based on the sub-path waveband grooming scheme. Simulation results show that, WGLAG not only can effectively save more switching ports to reduce the cost of OXC but also can obtain lower blocking probability than other algorithm.     

基于NS2多域ASON仿真平台设计与实现

对一个基于单域ASON仿真平台扩展实现了多域ASON仿真平台.通过对网络节点Id进行分域,实现了ASON中的多域分层网络结构,引入了一种基于全网抽象的路由信息汇聚策略.在ASON网络的分层路由中的每个路由域中加入备份Speaker节点,使网络具有更好的生存性.仿真测试表明当网络规模较大时,多域ASON网络在拓扑收敛速度、连接建立时间等方面的性能均优于单域.     

双链路故障时的共享路径保护

在波长路由光网络中,网络的存活性已经受到越来越多的重视.对单链路故障时的保护已经不能满足某些关键性业务对网络存活性的要求,因而研究了双链路故障时的共享路径保护技术.在动态业务下,将共享路径保护问题归结为整数线性规划.在节点无波长转换能力的情况下,分别提出了为当前业务计算最优路径和固定路径两种策略下的整数线性规划.数值结果表明,相对于专用保护,双链路故障时的共享路径保护能够节约30%左右的波长链路资源.     

Scheduling data aggregation trees to extend network lifetime in sensor networks

Increasing network lifetime (NL) is an important requirement in wireless sensor networks (WSNs). One of the techniques to extend NL is to use Data Aggregation Trees (DATs). DATs improve NL by combining the energy efficiency benefits of both Data Aggregation (DA) and tree‐based routing. While centralized and distributed strategies for DAT construction are widely used, we propose a combined approach for DAT construction to improve NL. The approach reduces the communication overhead and relaxes the requirement of complete network information at the sink. In the proposed work, this collaborative approach is termed as Extended Local View (ELV) approach. Two ELV‐based DAT construction algorithms termed as ELV with Fixed sink (ELVF) and ELV with Random sink (ELVR) are proposed. Both ELVF and ELVR use heuristics‐based technique of Local Path Reestablishment (LPR) and greedy‐based technique of Extended Path Reestablishment (EPR). Using these techniques a sequence of DATs are scheduled that collectively improve NL and also reduce the associated DAT reconstruction overhead. Performance of ELVF and ELVR is evaluated with rigorous experiments, and the simulation results show that the proposed algorithms have improved NL and are scalable across different DA ratio values. DAT schedule analysis further demonstrates reduced DAT reconstruction overhead of the proposed algorithms which illustrates its suitability for hostile and critical environments.     

光网络的动态特性与可扩展性

光网络正从静态光网络逐步演进为动态和智能的光网络,在演进过程中,光网络的动态特性越来越重要。一些可行的控制管理算法、策略和信令方法在网络规模扩大之后性能会严重恶化,因此光网络的可扩展性越来越受到研究者的重视。动态特性和可扩展性都是网络发展的需求,然而二者在存在一定的相互制约,通过建立分层分域的机制可以有效的环节这种制约,为实现动态特性良好、智能化程度高同时可扩展的光网络提供了可能。     

A New Shared Segment Protection Method for Survivable Networks with Guaranteed Recovery Time

Shared segment protection (SSP), compared with shared path protection (SPP), and shared link protection (SLP), provides an optimal protection configuration due to the ability of maximizing spare capacity sharing, and reducing the restoration time in cases of a single link failure. This paper provides a thorough study on SSP under the GMPLS-based recovery framework, where an effective survivable routing algorithm for SSP is proposed. The tradeoff between the price (i.e., cost representing the amount of resources, and the blocking probability), and the restoration time is extensively studied by simulations on three networks with highly dynamic traffic. We demonstrate that the proposed survivable routing algorithm can be a powerful solution for meeting stringent delay upper bounds for achieving high restorability of transport services. This can significantly improve the network reliability, and enable more advanced, mission critical services in the networks. The comparison among the three protection types further verifies that the proposed scheme can yield significant advantages over shared path protection, and shared link protection.     

Dynamic Routing and Wavelength Assignment in Survivable WDM Networks

Dense wavelength division multiplexing (DWDM) networks are very attractive candidates for next generation optical Internet and intelligent long-haul core networks. In this paper we consider DWDM networks with wavelength routing switches enabling the dynamic establishment of lightpaths between each pair of nodes. The dynamic routing and wavelength assignment (RWA) problem is studied in multifiber networks, assuming both protection strategies: dedicated and shared. We solve the two subproblems of RWA simultaneously, in a combined way using joint methods for the wavelength selection (WS) and wavelength routing (WR) tasks. For the WS problem in contrast to existing strategies we propose a new, network state based selection method, which tries to route the demand on each wavelength, and selects the best one according to different network metrics (such as available channels, wavelengths per fiber and network load). For the WR problem we propose several weight functions for using in routing algorithms (Dijkstra or Suurballe), adapting dynamically to the load of the links and to the length of the path. The combination of different wavelength selection and routing (WS&WR) methods enables wide configuration opportunities of our proposed algorithm allowing good adaptation to any network state. We also propose the extension of the RWA algorithm for dedicated and shared protection and a new method for applying shared protection in dynamic WDM environment. The detailed analysis of the strategies demonstrate that our RWA algorithm provides significantly better performance than previous methods in terms of blocking probability whether with or without protection methods.     

Evaluation of post-fault restoration strategies in multi-domain networks

Although multi-domain survivability is a major concern for operators, few studies have considered the design of post-fault restoration schemes. This paper proposes two such strategies, based upon hierarchical routing and signaling crankback, to handle single and multi-link failure events in multi-domain IP/MPLS networks (also extendible to optical DWDM networks). Specifically, the hierarchical routing strategy relies upon abstracted domain information to compute inter-domain loose routes, whereas the crankback scheme applies signaling re-tries to restore paths in a domain-by-domain manner. The performance of these proposed solutions is then analyzed and compared via simulation.     

An Efficient and Scalable Routing for MANETs

Recently, Distributed-Hash-Table (DHT)-based routing protocols have been proposed for large scale mobile ad hoc networks (MANETs). The motive behind using DHT is to avoid/reduce network wide flooding in MANETs in route discovery phase leading to achieve more scalable network. The challenge of deploying DHT at network layer for routing purpose in MANETs is to achieve more matching between logical and physical networks. The paper describes that existing DHT-based routing protocols for MANETs lack this feature. The paper presents a new DHT based scheme [called an efficient and scalable routing for MANETs (ESR)] which reduces the ill-matching between logical and physical networks. This is achieved be distributing the logical identifier (LID) space of DHT structure among the nodes such that the physical neighbors have consecutive LID space portions, i.e. all physical neighbors of a node are also the logical neighbors of the node. Therefore the logical ID space portion of a node may be non-contiguous. Based on this logical structure, a node builds up binary-search-tree (BST) using both logical ID space portion of itself and its neighbors. This BST at the node is traversed to find the next hop for a query/message. Through simulation, the paper shows the proposed approach (ESR) performs better than the existing one in term of routing overhead, average end-to-end delay, path-stretch values and false-negative ratio.     

A novel segment-shared protection algorithm based on dynamic domain-sequencing scheme for multi-domain optical mesh networks

Survivability has been widely recognized as an important design issue for optical networks. In practice, as the network scale keeps expanding, this design problem becomes more critical. Due to scalability and domain privacy, designing the protection scheme in multi-domain networks is more difficult than that in single domain networks. The path computation element (PCE) is known as an efficient architecture to compute optimal traffic engineering (TE) paths in multi-domain multilayer networks. Based on the PCE architecture, we first propose a new dynamic domain-sequencing scheme that considers the load balance of inter-domain links and then propose an improved segment-shared protection approach called DDSP. It can provide 100% protection ability for multiple failures that each single domain has only one failed link. Finally, the protection based on the optimal dynamic domain-sequencing scheme, called OPT, is designed, to evaluate performance of our algorithm and to provide the good bounding for the dynamic domain-sequencing scheme with limited intra TE information. Simulation evaluation shows that the proposed scheme is effective in multi-domain path protection with more efficient resource utilization, lower blocking probabilities and less inter-domain cost. Furthermore, the performance of it is near to OPT.