Inter-domain optical path provisioning with blocking avoidance by intra-domain immediate reroute-based semi-proactive hierarchical PCE

Optical fiber networks have become the foundations of communication system to provide enormous transmission capacity with less cost. Connection blocking is an inherent attribute and influences optical networks’ performance, especially in multi-domain network scenarios. We analyze the reason and effect of blockings including routing blockings and signaling blockings. We regard the cause of signaling blockings as the information asynchronization in resource reservation process. We define the concept of Information Asynchronization Period to describe the effect of signaling blockings. To reduce signaling blockings in end-to-end optical path provisioning for multi-domain scenarios, we propose a novel network routing and control scheme, named Intra-Domain Immediate Reroute based Semi-Proactive Hierarchical Path Computation Element (IDIRSP H-PCE). The proposed routing and control scheme mainly consists of two parts, Semi-Proactive routing and Intra-Domain Immediate Reroute mechanism. Dynamic network simulations verify our proposed scheme. We compare the network performance with Reactive Backward Recursive PCE-based Computation (BRPC) based PCE, Reactive H-PCE and Proactive H-PCE. Simulation results indicate that IDIRSP H-PCE can provide connection with a very low blocking probability in light load case, which is close to Proactive H-PCE, and obviously better than BRPC based Reactive PCE and Reactive H-PCE. For heavy load case, IDIRSP H-PCE has a remarkably lower blocking probability than other three methods. Moreover, we test our proposed routing and control scheme when facing link faults. Simulation results indicate that IDIRSP H-PCE can greatly improve the traffic access rate and optimize the network performance.     

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.     

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。     

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.     

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.     

SDI: a multi-domain SDN mechanism for fine-grained inter-domain routing

Software-defined networking (SDN) scheme decouples network control plane and data plane, which can improve the flexibility of traffic management in networks. OpenFlow is a promising implementation instance of SDN scheme and has been applied to enterprise networks and data center networks in practice. However, it has less effort to spread SDN control scheme over the Internet to conquer the ossification of inter-domain routing. In this paper, we further innovate to the SDN inter-domain routing inspired by the OpenFlow protocol. We apply SDN flow-based routing control to inter-domain routing and propose a fine-granularity inter-domain routing mechanism, named SDI (Software Defined Inter-domain routing). It enables inter-domain routing to support the flexible routing policy by matching multiple fields of IP packet header. We also propose a method to reduce redundant flow entries for inter-domain settings. And, we implement a prototype and deploy it on a multi-domain testbed.     

一种改进的多域光网络保护机制

生存性是保证业务服务质量的关键,多域光网络生存性问题中,由于存在多域间拓扑和路由信息不可见等约束,导致生存性实现较为困难.提出了将多域光网络进行逻辑聚合的思路,在此基础上分别针对域内和域间提出了非等值负载保护和M∶1保护机制.域内的非等值负载保护机制可以根据节点数以及业务量动态地分配保护路径,从而有效地提高资源利用率.     

Enhanced domain disjoint backward recursive TE path computation for PCE-based multi-domain networks

The ability of computing optimal routes poses new challenges when extending it to larger multi-domain network scenarios, as the quality of these computed end-to-end inter-domain routes depends on the selection of the domain sequence to be traversed. In the scope of the Internet Engineering Task Force (IETF), the Path Computation Element (PCE) Working Group has not provided definitive solutions to address the domain sequence selection problem, being still a work in progress. To this goal, the Path Computation Flooding (PCF) approach appears as a possible extension to Backward Recursive PCE-based Computation (BRPC) to calculate optimal end-to-end inter-domain paths without requiring a pre-configured domain sequence. Nonetheless, PCF presents major scalability issues in terms of network control overhead and path computation complexity, thus pleading for more accurate domain sequence selection techniques. This paper describes two novel mechanisms to establish inter-domain paths calculating the sequence of domains to be crossed when it is not known in advance. Both procedures make a good trade-off between the control overhead introduced and the accuracy of the computed end-to-end route. The obtained simulation results show the benefits of the proposed contributions, drastically reducing the control overhead while keeping the connection blocking probability close to the optimal values.     

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.     

P-cycle Protection in multi-domain optical networks

Providing resilient inter-domain connections in multi-domain optical GMPLS networks is a challenge. On the one hand, the integration of different GMPLS domains to run traffic engineering operations requires the development of a framework for inter-domain routing and control of connections, while keeping the internal structure and available resources of the domains undisclosed to the other operators. On the other hand, the definition of mechanisms to take advantage of such automatically switched inter-domain connectivity is still an open issue. This article focuses on the analysis of applicability of one of these mechanisms: P-cycle-based protection. The proposed solution is based on the decomposition of the multi-domain resilience problem into two sub-problems, namely, the higher level inter-domain protection and the lower level intra-domain protection. Building a P-cycle at the higher level is accomplished by certain tasks at the lower level, including straddling link connection, capacity allocation and path selection. In this article, we present several methods to realize inter-domain P-cycle protection at both levels and we evaluate their performance in terms of availability and spent resources. A discussion on a proposal of implementation of signalling based on extensions of existing protocols such as RSVP-TE and the PCE architecture illustrates the practical viability of the approach.