Optik 123 (2012) 1847–1851 Contents lists available at SciVerse ScienceDirect Optik jou rnal homepage: www.elsevier.de/ijleo Performance analysis of modified optical burst switching (OBS) ring network using dummy node Manoj Kumar Dutta ∗ , V.K. Chaubey EEE Department, BITS-PILANI, Pilani, Rajasthan, India a r t i c l e i n f o Article history: Received 27 September 2011 Accepted 29 February 2012 Keywords: Optical WDM network Optical burst switching Dummy node Ring networks Offered traffic a b s t r a c t In the present paper an analytical model of an optical burst switching ring network which is capable to handle the variable incoming traffic intelligently is presented. An efficient node architecture and net- work operating protocol enhances the data throughput in a congested network. Here we propose a node architecture to ease the traffic congestion in a ring network involving a dummy server connected to backbone of the ring topology to ease the traffic flow into the ring by diverting the packets under the congestion situation. An appropriate mathematical model for the proposed node architecture has been developed employing packet queuing control to estimate the amount of carried traffic for different node parameters and the analysis has been further extended to investigate the network performance under different signaling techniques. © 2012 Elsevier GmbH. All rights reserved. 1. Introduction Wavelength Division Multiplexing (WDM) technology [1] makes the optical channel to support enormous bandwidth which can further be utilized more effectively by introducing appropri- ate switching and multiplexing schemes. Optical burst switching (OBS) technology [2] has emerged as the most promising switch- ing paradigm for the core of IP over optical networks. The basic principal of optical burst switching is to separate the control chan- nels from data transmission channels to use the channel bandwidth more effectively. In an OBS network, client data packets are assem- bled into bursts and sent a short time after the corresponding control packet has been sent. The time between sending the control packet and the corresponding data burst is called the offset time, which can be either fixed or variable depending on the resource reservation protocol used. In OBS the basic transport unit is the burst, grouped by some quality of service (QoS) criteria. Bursts are assembled at the ingress nodes and their transmission is preceded by dedicated setup messages, one for each burst, transmitted on a dedicated control channel with the purpose of reserving bandwidth along the path for the upcoming data bursts. Based on the information carried by the setup messages, the intermediate nodes reserve switching resources along a pre-configured path, providing an opti- cal channel through which data bursts can be transmitted from ∗ Corresponding author. Tel.: +91 1596245073; fax: +91 1596244183. E-mail address: mkdutta13@gmail.com (M.K. Dutta). source to final destination after an adequate delay without any optical–electrical–optical (OEO) conversion [3–5]. Although promising, OBS still has implementation challenges, and shows a poor reliability in overloaded scenarios. It generally uses one-way reservation protocols in which data bursts are trans- mitted without confirmation that resources along the path will be successfully reserved and thus needing an end-to-end trans- port connection. Therefore, whenever the number of simultaneous reservation attempts exceeds the number of available resources, the successful transmission ceases to occur. Considerable efforts have been devoted to investigate various methods to handle such contention, including burst scheduling, optical buffering, burst segmentation, wavelength conversion, and deflection routing in the literature [6–11]. These are mainly reactive mechanisms requiring extra hardware and/or software compo- nents driven by burst contention at the network nodes and thereby increasing the cost and complexity. These requirements lead to a relatively higher cost in case of network scalability. In the present paper we have suggested modified node architecture using OBS ring network to achieve a simple and cost efficient solution. The important feature of the proposed model is the use of dummy node which helps the congested nodes to diverse their traffic as a resulting a reduced packet loss probability to achieve an improved throughput in the network. 2. OBS ring networks and node architecture Fig. 1 shows the OBS-ring network and its node architecture consisting of N nodes which are appropriately connected to a WDM link. A unidirectional ring network is assumed in which data are 0030-4026/$ – see front matter © 2012 Elsevier GmbH. All rights reserved. http://dx.doi.org/10.1016/j.ijleo.2012.02.046