Monitoring cycle design for fast link failure detection in all-optical networks

Fast link failure detection in all-optical networks (AONs) can be achieved using monitoring cycles (m-cycles). An m-cycle is a loop-back optical connection of supervisory wavelengths with a dedicated monitor. Compared to the channel-based or link-based monitoring schemes, m-cycle based schemes require much less number of monitors. In this paper, we propose an ILP (Integer Linear Program) formulation for m-cycle design to minimize the network cost. Our contributions are two-fold: 1) non-simple m-cycles are enabled; and 2) an efficient tradeoff is allowed between the monitor cost and the bandwidth cost. Numerical results show that our algorithm outperforms existing algorithms with a significant performance gain. © 2007 IEEE.published_or_final_versionIEEE Global Telecommunications Conference (GLOBECOM '07), Washington, DC, USA, 26-30 November 2007 p. 2315-231

Failure Localization Aware Protection in All-Optical Networks

The recent development of optical signal processing and switching makes the all-optical networks a potential candidate for the underlying transmission system in the near future. However, despite its higher transmission data rate and efficiency, the lack of optical-electro-optical (OEO) conversions makes fault management a challenge. A single fiber cut can interrupt several connections, disrupting many services which results in a massive loss of data. With the ever-growing demand for time-sensitive applications, the ability to maintain service continuity in communication networks has only been growing in importance. In order to guarantee network survivability, fast fault localization and fault recovery are essential. Conventional monitoring-trail (m-trail) based schemes can unambiguously localize link failures. However, the deployment of m-trail requires extra transceivers and wavelengths dedicated to monitoring the link state. Non-negligible overhead makes m-trail schemes neither scalable nor practicable. In this thesis, we propose two Failure Localization Aware (FLA) routing schemes to aid failure localization. When a link fails, all traversing lightpaths become dark, and the transceiver at the end node of each interrupted ligthpath issues an alarm signal to report the path failure. By correlating the information of all affected and unaffected paths, it is possible to narrow down the number of possible fault locations to just a few possible locations. However, without the assistance of dedicated supervisory lightpaths, and based solely on the alarm generated by the interrupted lightpaths, ambiguity in failure localization may be unavoidable. Hence, we design a Failure Localization Aware Routing and Wavelength Assignment (FLA-RWA) scheme, the Least Ambiguous Path (LAP) routing scheme, to dynamically allocate connection requests with minimum ambiguity in the localization of a link failure. The performance of the proposed heuristic is evaluated and compared with traditional RWA algorithms via network simulations. The results show that the proposed LAP algorithm achieves the lowest ambiguity among all examined schemes, at the cost of slightly higher wavelength consumption than the alternate shortest path scheme. We also propose a Failure Localization Aware Protection (FLA-P) scheme that is based on the idea of also monitoring the protection paths in a system with path protection for failure localization. The Least Ambiguous Protection Path (LAPP) routing algorithm arranges the protection path routes with the objective of minimizing the ambiguity in failure localization. We evaluate and compare the ambiguity in fault localization when monitoring only the working paths and when monitoring both working and protection paths. We also compare the performance of protection paths with different schemes in regards to fault localization

ILP formulation for p-cycle construction based on flow conservation

The concept of p-cycle (Preconfigured Protection Cycle) allows fast and efficient span protection in WDM mesh networks. To construct p-cycles, conventional algorithms need to enumerate all the candidate cycles in the network before ILP (Integer Linear Program) can be applied to find the optimal solution. To reduce the size of the candidate set and thus speed up the optimization process, heuristic algorithms are proposed for candidate cycle pre-selection at the cost of lower solution quality. Recently, some interesting ILP formulations were proposed to construct p-cycles without candidate cycle enumeration/preselection. But they tend to require a long running time. Following the approach of no candidate cycle enumeration, we formulate a new ILP based on flow conservation in this paper. Numerical results show that our new ILP runs much faster than the existing ones. © 2007 IEEE.link_to_subscribed_fulltex