RESEARCH ARTICLE A controllable deflection routing and wavelength assignment algorithm in OBS networks Philani Khumalo 1 • Bakhe Nleya 1 • Andrew Mutsvangwa 1 Received: 11 February 2019 / Accepted: 14 November 2019 / Published online: 23 November 2019 Ó The Author(s) 2019 Abstract Heterogeneous IoT-enabled networks generally accommodate both jitter-tolerant traffic and jitter-intolerant traffic. Optical burst-switched backbone networks are handling the resultant volumes of such traffic by trans- mitting it in huge-size chunks called bursts. Because of the lack or limited buffering capabilities within the core net- work, contentions as well as congestion may frequently occur, thus affecting overall supportable quality of service (QoS). Both contention and congestion will be character- ized by frequent burst losses, especially when traffic levels surge. The congestion is normally resolved by way of deflecting contending bursts to other less congested paths even though this may lead to differential delays incurred by bursts as they traverse the network. This will contribute to undesirable jitter that may ultimately compromise overall QoS. Noting that jitter is mostly caused by deflection routing which itself is a result of poor wavelength and routing assigning, in this paper we propose a controllable deflection routing scheme that allows the deflection of bursts to alternate paths only after controller buffer preset thresholds are surpassed. In this way, bursts intended for a common destination are always most likely to be routed on the same or least-cost path end-to-end. We describe the scheme and compare its performance to other existing approaches. Both analytical and simulation results overall show that the proposed scheme does lower both congestion and jitter, thus also improving throughput as well as avoiding congestion on deflection paths. Keywords Optical burst switching  Jitter  Deflection routing  Congestion Introduction In the OBS domain, primary concerns are in combating congestion as well as contention as bursts traverse the core network. In any given network, various types of conges- tion, e.g., nodal, CPU, path, may occur. Nodal congestion occurs when incident traffic overwhelms the serving node. CPU congestion is as a result of too many computations that jam the main CPU scheduler. Path or link congestion is caused by excessive traffic attempting to traverse the same path. In the context of OBS networks, congestion thus can be caused by several factors such as contention, uneven distribution of traffic leading to localized traffic overload, as well as improper provisioning of available resources such as in the case of routing and wavelength assignment (RWA). The presence of buffering capabilities at edge nodes makes it easy to combat edge congestion. Path congestion can be alleviated by way of dimensioning the available network resources such as wavelengths and links such that traffic is uniformly distributed throughout the network [1]. It is noted that contention will always occur at interior nodes when more than one data burst utilizing the same wavelength overlaps in time at the same single output port. Because of the buffer-less nature of such networks in their interior, different approaches are adopted to alleviate and combat contention. Primarily the contention resolution & Bakhe Nleya bmnleya@gmail.com Philani Khumalo philanipk@gmail.com Andrew Mutsvangwa amutsvangwa@gmail.com 1 Faculty of Engineering, Durban University of Technology, Durban, South Africa 123 J Opt (December 2019) 48(4):539–548 https://doi.org/10.1007/s12596-019-00578-2