Anna Urra

Protection performance components in MPLS networks

In this paper, we present a new methodology for evaluating fault recovery performance of some existing mechanisms, which considers the establishment of quality of service network paths with protection. In order to evaluate the level of protection of a network, different components, such as protection parameters (packet loss and restoration time), or network parameters and constraints (link failure probability and network load), are analyzed. A formulation to calculate the influence of each component in the establishment of protected paths is discussed in multiprotocol label switching (MPLS) networks. Several experiments are presented to support this formulation. Moreover, an analysis of the relationship between these protection components and different traffic classes is also introduced and justified.

Enhancing MPLS QoS routing algorithms by using the network protection degree paradigm

IP based networks still do not have the required degree of reliability required by new multimedia services, achieving such reliability will be crucial in the success or failure of the new Internet generation. Most of existing schemes for QoS routing do not take into consideration parameters concerning the quality of the protection, such as packet loss or restoration time. In this paper, we define a new paradigm to develop new protection strategies for building reliable MPLS networks, based on what we have called the network protection degree (NPD). This NPD consists of an a priori evaluation, the failure sensibility degree (FSD), which provides the failure probability and an a posteriori evaluation, the failure impact degree (FID), to determine the impact on the network in case of failure. Having mathematical formulated these components, we point out the most relevant components. Experimental results demonstrate the benefits of the utilization of the NPD, when used to enhance some current QoS routing algorithms to offer a certain degree of protection.

Enhanced multi-layer protection in multi-service GMPLS networks

This paper focuses on QoS routing with protection in an MPLS network over an optical layer. In this multi-layer scenario each layer deploys its own fault management methods. A partially protected optical layer is proposed and the rest of the network is protected at the MPLS layer. New protection schemes that avoid protection duplications are proposed. Moreover, this paper also introduces a new traffic classification based on the level of reliability. The failure impact is evaluated in terms of recovery time depending on the traffic class. The proposed schemes also include a novel variation of minimum interference routing and shared segment backup computation. A complete set of experiments proves that the proposed schemes are more efficient as compared to the previous ones, in terms of resources used to protect the network, failure impact and the request rejection ratio.

Enhancing fault management performance of two-step QoS routing algorithms in GMPLS networks

In this paper a novel methodology aimed at minimizing the probability of network failure and the failure impact (in terms of QoS degradation) while optimizing the resource consumption is introduced. A detailed study of MPLS recovery techniques and their GMPLS extensions are also presented. In this scenario, some features for reducing the failure impact and offering minimum failure probabilities at the same time are also analyzed. Novel two-step routing algorithms using this methodology are proposed. Results show that these methods offer high protection levels with optimal resource consumption.

Partial disjoint path for multi-layer protection in GMPLS networks

In this paper, different recovery methods applied at different network layers and time scales are used in order to enhance the network reliability. Each layer deploys its own fault management methods. However, current recovery methods are applied to only a specific layer. New protection schemes, based on the proposed partial disjoint path algorithm, are defined in order to avoid protection duplications in a multi-layer scenario. The new protection schemes also encompass shared segment backup computation and shared risk link group identification. A complete set of experiments proves the efficiency of the proposed methods in relation with previous ones, in terms of resources used to protect the network, the failure recovery time and the request rejection ratio.

Reliable services with fast protection in IP/MPLS over optical networks

Feature Issue on High Availability in Optical NetworksWe define new quality-of-service (QoS) routing schemes with protection in Internet Protocol (IP)/Multiprotocol Label Switching (MPLS) over optical networks. The novelty of the proposed routing schemes is the use of the knowledge of the logical links already protected by the optical layer. The logical topology defined by the optical layer is given and fixed, and we assume that it is partially protected. Thereby, at the IP/MPLS layer, spare capacity is reserved to protect only those links that are unprotected. Moreover, we also characterize the traffic services based on their level of reliability and QoS requirements. In order to guarantee fast protection, segment protection and shared backups are combined, resulting in suitable fault recovery time and resource consumption. A complete set of experiments proves that the proposed schemes are more efficient than the previous ones in terms of resources used to protect the network, failure impact, and blocking probability.

Enhanced protection using shared segment backups in a multiservice GMPLS-based networks

The paper presents a novel protection methodology for setting protected paths in a multiservice GMPLS-based network scenario. By applying the proposed methods, label switched paths can be protected to obtain small failure probabilities and fast failure recovery time. The presented methodology allows classifying the required protection level depending on the traffic class. Another important development is the fact that considers protection at a WDM level by not overprotecting paths, which are already protected at this level. The proposed routing algorithms strictly restrict the backup path computation to one shared segment per path, optimizing the resource consumption and simplifying the failure management. A complete set of experiments proves the efficiency of the proposed method in relation with previous ones, in terms of the percentage of resources used to protect the network and the request rejection ratio.

Service Level Agreement Framework for Differentiated Survivability in GMPLS-based IP-over-Optical Networks

In the next generation optical internet, GMPLS-based IP-over-optical networks, ISPs will be required to support a wide variety of applications each having their own requirements. These requirements are contracted by means of the SLA. This paper describes a recovery framework that may be included in the SLA contract between ISP and customers in order to provide the required level of survivability. A key concern with such a recovery framework is how to present the different survivability alternatives including recovery techniques, failure scenario and layered integration into a transparent manner for customers. In this paper, two issues are investigated. First, the performance of the recovery framework when applying a proposed mapping procedure as an admission control mechanism in the edge router considering a smart-edge simple-core GMPLS-based IP/WDM network is considered. The second issue pertains to the performance of a pre-allocated restoration and its ability to provide protected connections under different failure scenarios.

Minimum interference routing with fast protection

One of the most effective techniques offering QoS routing is minimum interference routing. However, it is complex in terms of computation time and is not oriented toward improving the network protection level. In order to include better levels of protection, new minimum interference routing algorithms are necessary. Minimizing the failure recovery time is also a complex process involving different failure recovery phases. Some of these phases depend completely on correct routing selection, such as minimizing the failure notification time. The level of protection also involves other aspects, such as the amount of resources used. In this case shared backup techniques should be considered. Therefore, minimum interference techniques should also be modified in order to include sharing resources for protection in their objectives. These aspects are reviewed and analyzed in this article, and a new proposal combining minimum interference with fast protection using shared segment backups is introduced. Results show that our proposed method improves both minimization of the request rejection ratio and the percentage of bandwidth allocated to backup paths in networks with low and medium protection requirements

Multi-layer network recovery: avoiding traffic disruptions against fiber failures

The next generation backbone networks, optical IP/MPLS networks, enable increasingly higher volumes of information to be transported. In this network architecture, a fiber failure can result in a loss of several terabits of data per second and leads to multiple failures in the upper network layer. Thus, the ability of the network to maintain an acceptable level of reliability has become crucial. In this paper, a dynamic cooperation between packet and wavelength switching domain is considered in order to provide protected paths cost effectively. A new multi-layer routing scheme that incorporates recovery mechanisms in order to guarantee connectivity against any single fiber failure is presented.