Tu.4.D.3.pdf ECOC Technical Digest © 2012 OSA Experimental Evaluation of a Dynamic PCE-Based Regenerator-Efficient IA-RWA Algorithm in Translucent WSON A. Castro 1* , R. Martínez 2 , L. Velasco 1 , R. Casellas 2 , R. Muñoz 2 , J. Comellas 1 (1) Universitat Politècnica de Catalunya (UPC), Barcelona (Spain), Email: acastro@ac.upc.edu (2) Centre Tecnològic de Telecomunicacions de Catalunya (CTTC), Castelldefels (Spain) Abstract We devise a novel dynamic PCE-based impairment-aware RWA algorithm in translucent GMPLS WSON that minimizes regenerator usage. Experimental evaluation carried out on the Open GMPLS/PCE control plane of CTTC ADRENALINE test-bed shows that significant improvements (>340%) are attained in terms of the offered traffic load. Introduction Translucent networks allow deploying regional- scale, e.g. European, optical networks meeting end-to-end quality of transmission (QoT) of optical signals. 3R regenerators are placed at some intermediate nodes and used when a signal needs to be electrically regenerated before arriving to the receptor. Being regenerators expensive resources 1 their use must be optimized. When optical signals are propagated from transmitter to receiver its QoT is degraded as a result of physical layer impairments which might cause high bit error rate (BER) at the receiver. QoT can be evaluated at the destination node of a lightpath by computing the optical signal-to- noise ratio (OSNR) 1 . Translucent wavelength-switched optical networks (WSON) can be controlled by using the GMPLS protocol suite so to set-up and tear down optical connections dynamically 2 . In that context, impairment-aware routing and wavelength assignment (IA-RWA) algorithms have been proposed in the literature to compute end-to-end translucent optical connections consisting in a succession of transparent lightpaths that meet some OSNR requirement 1,3 . Each lightpath is computed by solving the IA- RWA problem subject to the wavelength continuity constraint (WCC). A centralized Path Computation Element (PCE) can be used to solve the IA-RWA problem on demand. PCE is called to find routes and wavelength assignments meeting the required OSNR threshold for incoming connection requests. To this end, the Traffic Engineering Database (TED) containing the status of the resources in the network can be used. In this paper we focus on dynamic translucent WSON and devise and experimentally evaluate a novel dynamic PCE-based IA-RWA algorithm which minimizes regenerators usage. Translucent IA-RWA proposed algorithm Before describing the IA-RWA problem, we need to introduce some notation. We are given a TED describing the network topology and the state of the resources (wavelength channels at every link and regenerators availability at every node). We represent that network topology by the graph G(N, E, W), where N is the set of optical nodes, E is the set of optical links, and W is the set of wavelengths. Let N R ⊆N be the subset of nodes with regeneration capability, and conversely N T ⊆N the subset of nodes without regeneration capability. Thus N=N R ∪N T . Additionally, we are given a pair of source and destination nodes {s,t} for the connection being requested. The IA-RWA problem consists in finding a feasible route and wavelength assignment for the requested connection, so to minimize the number of regenerators needed to guarantee the QoT for that connection. As a secondary objective, the length of the route, in terms of number of hops, should be minimized. To fulfill the regenerators minimization objective, we build an auxiliary directed graph (digraph) D st (N st , A), where N st =N R ∪{s,t} and A is the set of directed arcs. Each arc a=(u,v)∊A connects two nodes u,v∊N st , where u∊N R ∪{s} and v∊N R ∪{t}. An arc a=(u,v) exists only if a feasible lightpath can be found between u and v in G, where the route has an acceptable OSNR level and the WCC is satisfied. For illustrative purposes, Fig. 1 shows an example of auxiliary digraph construction. There, digraph D st is built upon the reception of a connection request between nodes s and t. To this end, the set N R with those nodes with regeneration capabilities currently available (colored circles) and nodes s and t belong to N st . Directed arcs are created connecting s and nodes in N R to t and other nodes in N R , provided that a feasible lightpath exists in G. In such scenario, routes {s,2,t} and {s,5,t} minimize the number of regenerators used. Note that other routes, such as {s,2,6,t}, being feasible,