Enhancing the Carrying Capacity of a DWDM Network Yingzhen Qu, Pramode K. Verma and John Y. Cheung The University of Oklahoma, Tulsa Telecommunications Systems, College of Engineering 4502 E 41 st St, Tulsa, OK 74135 yingzhenqu@ou.edu , pverma@ou.edu , jcheung@ou.edu Abstract Routing and wavelength assignment problems occupy a central place in the design of DWDM networks. More recent studies have proposed means to achieve fairness among traffic classes that traverse multiple nodes over a light-path operating under the wavelength continuity constraint. This paper focuses on the traffic carrying capacity of the network as a whole, and it proposes means to enhance the same using techniques of wavebanding and preferential treatment to different classes of traffic. We use example topologies to illustrate the impact of different disciplines on traffic classes. 1. Introduction As demand for bandwidth increases, the optical technology increasingly becomes the technology of choice for telecommunication networks. In an all-optical network, signals are transmitted from the source node to the destination node without being converted into the electrical domain. The DWDM (Dense Wavelength Division Multiplexing) technology has increased the bandwidth of a fiber by two-to-three orders of magnitude by allowing the simultaneous transmission of multiple wavelengths. A DWDM network consists of optical add- drop multiplexers (OADMs) and/or optical cross- connects (OXCs) connected by optical fiber links. A light-path is an optical path established between two nodes that creates a bandwidth equivalent to a single or multiple wavelengths between them. There are two steps involved in establishing a light-path in DWDM networks: routing and wavelength assignment (RWA). Routing finds a route from the source node to the destination node. Wavelength assignment assigns a single wavelength or a set of wavelengths to the route. A connection request is said to be blocked if there is no free wavelength on the available paths between the corresponding node pair. The RWA problem has been extensively studied [1-3, 6]. The objective of RWA is to maximize the number of connections that are established in the network at any time within the constraint of a fixed number of available wavelengths. This paper focuses on the traffic carrying capacity of the network as a whole, and it proposes means to enhance the same using techniques of wavebanding and preferential treatment to different classes of traffic. We use example topologies to illustrate the impact of different disciplines on traffic classes. The paper is organized as follows: The next section, Section 2, reviews the fairness problem discussed in a recent paper [2, 5, 9]. In Section 3, we propose a new method to enhance the carrying capacity of an all-optical network as a whole. Section 4 illustrates its efficacy with example topologies. We present our conclusion in Section 5. 2. Classes of Traffic and Fairness Recent studies [1, 5] have reported that traffic requiring a larger number of hops between the source and the destination suffers a higher blocking probability. This has been referred to as the fairness problem. Among the means to address fairness is the technique of protection threshold [5], where the single-hop traffic is assigned an idle wavelength only if the number of idle wavelengths on the link is at or above a given threshold. Since the blocking probability grows fast as the number of hops increases, in order to obtain the same quality of service on the multi-hop traffic as the single-hop traffic, the multi- hop traffic route has to be “protected”. In [2], the traffic classification and service (ClaServ) method was proposed to solve the fairness problem. The traffic requests are classified depending on the number of hops from the source node to the destination node. The classified traffic requests receive different levels of priority, providing preferential treatment to multi-hop traffic. Reference [2] uses Waveband Access Range and Waveband Reservation methods to achieve acceptable blocking probability for multi-hop traffic, resulting in multi-hop traffic occupying more wavebands. 3. Service and Hops (S-Hops Method In this paper, we focus on increasing the traffic carrying capacity of the network as a whole, as opposed to equalizing the blocking probability of different classes Proceedings of the 2004 International Conference on Parallel Processing Workshops (ICPPW’04) 1530-2016/04 $20.00 © 2004 IEEE