Optical Switching and Networking 8 (2011) 242–248 Contents lists available at SciVerse ScienceDirect Optical Switching and Networking journal homepage: www.elsevier.com/locate/osn A dynamic and quasi-centralized RWA method for optical fast circuit switching networks employing route pre-prioritization Hiroaki Ohno ∗ , Hiroshi Hasegawa, Ken-ichi Sato Department of Electrical Engineering and Computer Science, Nagoya University, Furo-cho, Chikusa-ku, 464-8603, Japan article info Article history: Available online 22 June 2011 Keywords: Optical fast circuit switching Dynamic network control Routing and wavelength assignment Quasi-centralized control abstract We propose a new dynamic RWA algorithm for optical fast circuit switching networks, agile optical networks that can accommodate changing broadband demands. The algorithm utilizes pre-computed prioritized route candidates that reflect statistical information such as traffic distribution characteristics to attain better load balancing. The route priority is periodically distributed over a network and RWA for each path connection demand is processed in a distributed manner. Numerical experiments demonstrate that the algorithm matches the performance of a centralized RWA algorithm that uses all the necessary information on a network. © 2011 Elsevier B.V. All rights reserved. 1. Introduction Broadband access is being rapidly adopted throughout the world and, as a result, traffic is continually increasing. On-demand bandwidth provisioning services such as Opti- cal Mesh Service provided by AT&T [1] and JiT (Just in Time) service by Verizon [2] have also been developed. These services require agile network reconfigurability, which is now realized with digital cross-connect systems. Photonic networks using ROADMs that can route optical paths dy- namically are being introduced to create bandwidth abun- dant and energy efficient networks [3]. Further traffic expansion will occur in the near future with the pen- etration of new broadband services including ultra-high definition video (raw bit rate of 72 Gbps per channel) distribution [4], 4-k cinema (6 Gbps per channel) [5], Grid- computing, and e-science. For accommodating such agile and bandwidth-demanding services, the dynamic reallo- cation of wavelength paths will be necessary. The re- sulting networks will achieve not only large bandwidth but also QoS-guaranteed connections. Thus Optical fast Circuit Switching (OCS) technology (path and circuit are used interchangeably in this paper) will play a key role ∗ Corresponding author. E-mail address: h_oono@echo.nuee.nagoya-u.ac.jp (H. Ohno). in the future networks [6]. In OCS networks, wavelength paths are utilized to directly accommodate the bandwidth- demanding services and a connection is setup immediately upon service request arrival. The algorithm presented here utilizes pre-calculated route candidates between all source and destination pairs, and route candidates are updated at certain time intervals, say every hour. Therefore, a route can be determined immediately for each new connection request. Each node on the route simply checks spare wave- lengths and the related signaling is very simple. As a re- sult, connection setup time is small. OCS generally needs to handle a large number of optical paths, and a sophisticated optical path control algorithm must be developed that can fully utilize a given set of resources. A lot of effort has been devoted for developing efficient algorithms to design optical path networks including OCS networks. The design problems can be classified into two classes, static [7,8] and dynamic [9–19] ones, where the latter is applied to OCS network design. The general objective of static network design is to minimize the amount of total network resources used to accommodate given wavelength path connection demand. The difficulty in resource minimization lies in the assignment of routes and wavelengths to optical paths, which is related to the graph coloring problem [20]; it was proved to be NP- complete [21]. On the other hand, the general objective of dynamic network design is to minimize blocking 1573-4277/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.osn.2011.06.001