Spare capacity modelling and its applications in survivable iP-over-optical networks

As the interest in IP-over-optical networks are becoming the preferred core network architecture, survivability has emerged as a major concern for network service providers; a result of the potentially huge traffic volumes that will be supported by optical infrastructure. Therefore, implementing recovery strategies is critical. In addition to the traditional recovery schemes based around protection and restoration mechanisms, pre-allocated restoration represents a potential candidate to effect and maintain network resilience under failure conditions. Preallocated restoration technique is particularly interesting because it provides a trade-off in terms of recovery performance and resources between protection and restoration schemes. In this paper, the pre-allocated restoration performance is investigated under single and dual-link failures considering a distributed GMPLSbased IP/WDM mesh network. Two load-based spare capacity optimisation methods are proposed in this paper; Local Spare Capacity Optimisation (LSCO) and Global Spare Capacity Optimisation (GSCO)

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

A CTMC-based characterisation of the propagation of errors in GMPLS Optical Rings

Abstract: This article presents a Continuous-Time Markov Chain model to characterise the propagation of failures in optical GMPLS rings. In order to characterize the behaviour of failure propagation epidemic-based models are commonly used. However, the existing epidemic models do not take into account the specific features of a multilayer network environment. A node failure in GMPLS-based networks can affect: Control Plane and Data plane reporting different failures scenarios. Consequently, an extended generic epidemic model called SID is proposed, in order to cover multiple failures and recovered states in a GMPLS Multilayer scenario. The CTMC model takes into account the SID model and provides a set of design rules to specify the values of repair rates required to achieve a given service availability, assuming a certain infection and disable rate.The work described in this paper was carried out with the support of the BONE project (''Building the Future Optical Network in Europe''), a Network of Excellence funded by the European Commission through the 7th ICT-Framework Programme. Additionally, the authors would like to thank the support of the T2C2 Spanish project (under code TIN2008-06739-C04-01) and the Madrid Community through the MEDIANET project (S-2009/TIC-1468) to the development of this work. This work is partially supported by Spanish Ministry of Science and Innovation project TEC 2009-10724 and by Generalitat de Catalunya research support program (SGR-1202).Publicad

Analysis of RSVP-TE graceful restart

GMPLS is viewed as an attractive intelligent control plane for different network technologies and graceful restart is a key technique in ensuring this control plane is resilient and able to recover adequately from faults. This paper analyses the graceful restart mechanism proposed for a key GMPLS protocol, RSVP-TE. A novel analytical model, which may be readily adapted to study other protocols, is developed. This model allows the efficacy of graceful restart to be evaluated in a number of scenarios. It is found that, unsurprisingly, increasing control message loss and increasing the number of data plane connections both increased the time to complete recovery. It was also discovered that a threshold exists beyond which a relatively small change in the control message loss probability causes a disproportionately large increase in the time to complete recovery. The interesting findings in this work suggest that the performance of graceful restart is worthy of further investigation, with emphasis being placed on exploring procedures to optimise the performance of graceful restart

Failure propagation in GMPLS optical rings: CTMC model and performance analysis

Network reliability and resilience has become a key design parameter for network operators and Internet service providers. These often seek ways to have their networks fully operational for at least 99.999% of the time, regardless of the number and type of failures that may occur in their networks. This article presents a continuous-time Markov chain model to characterise the propagation of failures in optical GMPLS rings. Two types of failures are considered depending on whether they affect only the control plane, or both the control and data planes of the node. Additionally, it is assumed that control failures propagate along the ring infecting neighbouring nodes, as stated by the Susceptible-Infected-Disabled (SID) propagation model taken from epidemic-based propagation models. A few numerical examples are performed to demonstrate that the CTMC model provides a set of guidelines for selecting the appropriate repair rates in order to attain specific availability requirements, both in the control plane and the data plane.This work is partially supported by the Spanish Ministry of Science and Innovation project TEC 2009-10724 and by the Generalitat de Catalunya research support programme (SGR-1202). Additionally, the authors would like to thank the support of the T2C2 Spanish project (under code TIN2008-06739-C04-01) and the CAM-UC3M Greencom research grant (under code CCG10-UC3M/TIC-5624) in the development of this work.Publicad