Performance analysis and experiments of distributed dynamic routing in GMPLS controlled optical networks

Abstract

ABSTRACT This paper investigates the efficiency of deploying distribut ed dynamic routing with different adaptive weight functions using the GMPLS control plane in optical transport networ ks. Improved TAW function is presented. The limitations of employing adaptive weight functions are also va lidated compared to direct routing. Keywords: GMPLS Controlled Optical Networks, Adaptive We ight Functions, Distributed Dynamic Routing 1. INTRODUCTION GMPLS(Generalized Multiprotocal Label Switching ) is constructed as the op tical control plane w ith Open Short Path First with Traffic Engineering(OSPF-TE) for distributed routing, Resources Reservation Protocol with Traffic Engineering(RSVP-TE) for signaling, and Link Management Protocol (LMP) for auto-discovery. [1]. GMPLS controlled optical networks is an important representa tive of next generation optical networks for it could enable capabilities such as rapid provisioning, eff ective traffic engineering and distributed fault management th at are needed to enable advanced services, such as BoD, Enhanced Private Line (EPL), grid computing and OVPN services[2] .A testbed of such a intelligent optical networks named AMSON(Adaptive Multi- Service Optical Network)ha s been developed [3] . In peer-to-peer GMPLS controlled WDM optical networks, every router maintains a database of network topology information to calculate lightpaths for connection requests. As for the distributed dynamic routing, each node keeps a global view of the network topology within its routing domain. When a new lightpath is set up or released, there will be a change in link state information which should be advertised to all other routers through flooding [4], thus Traffic engineering (TE) database is updated as the link bandwidth changes. While for the direct routing, we mean there is no bandwidth information updated, hence each node maintains a st atic routing table to provide fixed next-hop information. SPF algorithm is used in each no de to calculate the end-to-end pa th upon receiving a call request. In the SPF algorithms, such as Dijkstra’s shortest path algor ithm, every link in the network is associated with a weight, for example, the propagation delay of the link. For the distributed dynamic routing in GMPLS controlled optical networks, WDM specific information such as number of available wavelengths and total wavelengths on a given link can be incorporated in the weight functions to minimize th e congestion or blocking probab ility and improve performance. Adaptive weight functions such as TAW, AW, LRW, which c onsider WDM specific information such as distance, hop, the number of available wavelengths and total wavelengths on a given link have been proposed [5-10]. TAW algorithm calculates weights based on to tal wavelengths and availa ble wavelengths. However, it is not accurate at the critical point when available wavelengt hs equals to total wavelengths. Moreover, the efficiency of employing such adaptive weight functions in actual GMPLS environment has not been investigated yet. In our paper, improved TAW (ITAW) function is presented which shows a better performance in lightpath establishment. Extensive experiments were made to analyze limitations of employing adaptive weight functions in GMPLS controlled optical networks. The remainder of the paper is organized as follows. Section 2 presents a summary of other studies of the dynamic routing with adaptive weight functions. Section 3 presents a general view of the experiment and simulation testbed. Section 4 presents the improvement of TAW function. Section 5 presents the performance evaluation and results. Finally, the conclusions of this paper are given in Section 6.