Fault Detection in Optical Network & Fault Recovery in IP-over WDM Network

Fault Detection in Optical Network

Problem Synopsis
The fault detection in optical network is an important issue and a prerequisite to fault recovery process. Due to high data rates, even a short service disruption may cause large amount of data to be affected. Many different types of service disruptions occur frequently in practice. Therefore, it is of critical importance for such networks to have fast and effective methods for identifying and locating failures. Fault detection mechanisms in optical layer depend on alarms generated by different types of network monitoring equipment. Depending on the placement and capabilities of these monitoring devices, the network fault detection system may receive a large number of redundant alarms for some failures in the network, while it may not receive any fault notification for other failures. In an optical network faults propagate in the optical domain, while alarms are generated and processed in the electrical domain. A single fault can propagate throughout an optical network and generate many simultaneous alarms. This complicates the problem of accurately locating the source of the fault. All networks require some form of fault detection system, which is capable of detecting and locating failures in a network. The function of such a system is to process alarms received from network components, and based on this information determine all possible locations of failure. Its effectiveness is measured by the speed with which it is able to process the received alarms, as well as by its ability to unambiguously provide fault source location. Therefore, we need to have a fault detection model to detect faults in a minimum time.

Expectation from Student
Student must have good background in optical network and algorithms; she/he must also have proficiency in programming and have very good grades in the under-graduate studies.

At the end of thesis, the student must write a technical report and present the work in a seminar for final evaluation of his/her thesis. Finally, submission of his/her work to the conference is strongly recommended.

Total time of thesis work: 20 weeks full time

Location of the work: The student will work at Laboratory for Communication Networks, IMIT, KTH


Fault Recovery in IP-over WDM Network

Problem Synopsis
We consider an IP-over-WDM network in which network nodes consist of optical crossconnects and IP routers. Nodes are connected by fibers to form a mesh topology. Any two IP routers in this network can be interconnected together by an all-optical wavelength-division multiplexing (WDM) channel, called a lightpath, and the collection of lightpaths that are set up form a virtual topology. The design of survivable optical networks is obtained by exploiting recovery schemes in the WDM and IP layers. Upon network failure, a recovery scheme dynamically looks for backup paths of spare capacity (i.e., back-up capacity) in the network. A protection scheme reserves, in advance, dedicated backup paths and wavelengths in the network. The former scheme is mainly used at higher layers (e.g., the IP layer). The latter scheme is commonly used at the optical (e.g., WDM) layer. Since each lightpath is expected to operate at a rate of few gigabits per second, a fiber (link) failure can cause a significant loss of bandwidth and revenue. Thus, the network designer must provide a fault recovery technique that combats failures.

In this work, we will propose a recovery scheme for a single failure in IP-over-WDM network. This scheme will be an optimization problem with the aim of providing restoration (recovery) capabilities in this network. The objective of this scheme is to determine a set of back-up resources (capacity) that minimizes the subscription of these resources on links and paths to route the demand services (traffic) during restoration. In this approach, we will determine the total back-up resources (capacity) in the network and consequently build-u