Regular Articles A traffic-depended multi-buffer node architecture and an effective access technique under symmetric and asymmetric IP traffic scenarios for unslotted ring WDM MANs Peristera A. Baziana School of Electrical and Computer Engineering, Department of Communications Electronic & Information Engineering, National Technical University of Athens, 157 73 Zografou, Athens, Greece article info Article history: Received 9 January 2016 Revised 21 May 2016 Accepted 20 June 2016 Keywords: Asynchronous transmission Access strategy Asymmetric traffic Bandwidth exploitation Metropolitan area network Variable packet size Wavelength division multiplexing abstract This study aims to put forward an extensive discussion about the increasing demand for available band- width to serve the multiple types of traffic in modern wavelength division multiplexing (WDM) metropolitan area networks (MANs). A traffic-depended multi-buffer node architecture in conjunction with an efficient asynchronous transmission WDM access (WDMA) protocol to serve the variable size Internet packets in ring MANs is proposed. The structure of the multi-buffer node architecture is deter- mined by the probability distribution of each packet size category in the MAN traffic, providing storage and dropping events equity among the nodes. The adopted WDMA algorithm satisfies the requirement for high performance efficiency especially under high offered load, by taking care to optimally face the bandwidth fragmentation problem and to maximize the bandwidth exploitation, while it effectively avoids both the packets collisions over the wavelengths and the destination conflicts. Numerical results prove that the proposed network model achieves throughput improvement up to 334% as compared with the relative study of Pranggono and Elmirghani (2011). An analytical framework is developed for the pro- tocol throughput predictions under both symmetric and asymmetric IP traffic scenarios. Also, the pro- posed protocol performance is thoroughly investigated through simulation results based on Poisson and self-similar traffic model statistics, for both traffic scenarios. Ó 2016 Elsevier Inc. All rights reserved. 1. Introduction Cotemporary telecommunication networks are principally char- acterized by the explosive growth of bandwidth demands in order to serve a wide range of heterogeneous traffic from diverse ser- vices, mainly consisted of multiple real-time and time-sensitive Internet Protocol (IP) applications with guaranteed Quality of Ser- vice (QoS). Especially, modern Metropolitan Area Networks (MANs) of ring topology and backbone networks are mostly com- missioned with the constantly increasing IP traffic, as a result of the unprecedented rapid augmentation of Internet services and users population. Thus, the requirement for a transmission tech- nology capable of handling the enormous traffic demands satisfy- ing the requisite QoS is paramount. Wavelength Division Multiplexing (WDM) technique [1] has been proven as the domi- nant prospective technology for high-speed bandwidth-efficient MANs development based on the optical technology latest achievements. In recent WDM implementations the data rate per wavelength has reached several hundreds of Gb/s, while in the near future MAN implementations even of 100 Gb/s are expected to be supported. Key role to a WDM MAN performance plays the access node architecture in conjunction with the WDM access (WDMA) control protocol applied. Particularly, the convergence of each wavelength transmission data rate with the resources electronics processing rate is required in order for the transmitted packets to be properly received and processed by the intermediate nodes and the destina- tion. Two main access node network interfaces are followed in recent research studies: (1) the TT-FR one, i.e. each access node is equipped with a tunable transmitter and a fixed receiver, while a dedicated home wavelength for reception has been assigned to it avoiding the receiver collisions [2–5], and (2) the FT-TR one, i.e. each access node is equipped with a fixed transmitter and a tun- able receiver, while a dedicated home wavelength for transmission has been assigned to it avoiding the wavelength collisions [6–7]. Although both access node network interfaces aim to arbitrate the access over the wavelengths avoiding collisions, they provide bandwidth waste. This is because they restrict the transmission http://dx.doi.org/10.1016/j.yofte.2016.06.006 1068-5200/Ó 2016 Elsevier Inc. All rights reserved. E-mail address: baziana@central.ntua.gr Optical Fiber Technology 31 (2016) 92–110 Contents lists available at ScienceDirect Optical Fiber Technology www.elsevier.com/locate/yofte