Multicast RSA Algorithm with Defragmentation for Elastic Optical Networks (work in progress)

Resumo

Elastic Optical Network (EON) is a new paradigm proposed in [2] to improve the use of the spectrum in the current optical fibers. They propose to change the static allocation of the spectrum to the connection requests, by a dynamic and flexible allocation according to the demand, granting to each user the exact amount of spectrum that bandwidth request. The main focus of study in EON is algorithms design that perform the routing of pointto-point (unicast) request, and the assignment of spectrum [2] also known as Routing and Spectrum Assignment (RSA). EON networks impose optical layer constraints: continuity, contiguity and non-overlapping of spectrum allocation. In the context of dynamic traffic, optimum solutions can not be calculated due to short time to answer the requests. Therefore, blocking of requests occurs because to spectrum fragmentation, being one of the main problems of EON [1]. In a very fragmented network the available spectrum is not entirely contiguous, so the optical layer constraints make it impossible to complete the requests. A summary of the algorithms that reorganize or defragment the EON networks can be founded in [1].

The implementation of point-to-multipoint (multicast) services in EON, such as teleconferences, mass data transport, server migrations, and others, are performed through the Multicast RSA (MC-RSA) algorithms [4]. Multicast traffic increases network fragmentation much faster than the unicast traffic. In our study of the-state-of-the-art, in [3], a solution has been presented for this problem, where network fragmentation is measured each time a traffic request arrives, and this is assigned to less-fragmented spectrum block. However, when a blocking happen this approach does not performance any action. The above-mentioned proposal does not solve completely the fragmentation problem, as each new arrived request will still increasing network fragmentation. Specifically, the literature only proposes defragmentation strategies for unicast traffic, leaving open the design of defragmentation strategies for a multicast context.