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Faculty of Engineering and Built Environment

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    A routing and wavelength assignment (RWA) scheme for deflected bursts in optical burst switched networks
    (Turkish Online Journal of Qualitative Inquiry (TOJQI), 2021-11-01) Nleya, Bakhe; Gomba, Masimba
    All Optical Burst Switched (OBS transport networks are often characterized by frequent occurrences of both contention and wavelength congestion. Their occurring often leads to degradations in overall network performance in handling moderate to high traffic levels, and all this leading to increases in data burst losses. Deflection routing contention resolution is quite popular in combating both types of congestions and ultimately leading to improvements in overall network throughput. However, it is necessary that network throughput always balance with effective utilization. In this paper, we propose a prioritized (indexed) cooperative based routing and wavelength assignment (PIC-RWA) scheme that reduce both contention and wavelength congestions. Performance results indicate that it significantly improves overall network performance in terms of improved effective resources utilization
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    A limited intermediate node buffering based RWA scheme in OBS backbone networks
    (Ponte Academic Journal, 2019-11) Nleya, Bakhe; Mutsvangwa, Andrew
    An all optical backbone Optical Burst Switched (OBS) network comprises of a multitude of optical transport sub-systems erected in commercial, residential as well as industrial ar-eas. The heterogeneous nature of the large volumes of traffic gen-erated by various applications and services ideally requires an op-tical backbone network infrastructure to accommodate it. Such a network must be continuously adaptable to the changing nature of the traffic as well as its spontaneous growth with time. In so doing, it has to ensure high end-to-end quality of service (QoS), availabil-ity as well as provision adaptable controllability in cooperation with peripheral (service) layer networks. To successfully design and deploy a cost-effective backbone network, consideration must be taken with regards to system configuration, as well as in applied devices manufacturing. This is to ensure that any component failure does not add any noticeable performance degradation as the network will quickly reconfigure itself accordingly. At operational level, ef-fective routing approaches are necessary to ensure minimized con-gestion as well as contention occurrences. The aggregation of both transit and local traffic at a node influences each other such as to aggravate congestion and to a certain extent reduce contention oc-currences (due to the streamline effect). In this paper, we propose a priority based intermediate Node Buffering based PIB-RWA scheme to combat the problem of contention occurrences and to prevent bursts discarding. It basically selects primary as well as deflection paths/links based on past contention frequency occurrences as well as current resources states in the candidate paths. Furthermore, the scheme also augments intermediate buffering provisioning for con-tending data bursts that are almost reaching the destination. Simu-lation results show that the scheme performs well in terms of key QoS metrics such as network throughput, data burst loss probabil-ities as well as load balancing.
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    A bursts contention avoidance scheme based on streamline effect awareness and limited intermediate node buffering in the core network
    (Blue Eyes Intelligence Engineering and Sciences Publication, 2020-08-30) Nleya, Bakhe; Chidzonga, Richard F.
    In an Optical Burst Switched (OBS) network, data packets sourced from peripheral networks are assembled into huge sized data bursts. For each assembled data burst, an associated control signal in the form of a burst control packet is (BCP) is gen-erated and scheduled at an offset time ahead of the data burst. The offset timing is to allow for the pre-configuration of required re-sources at all subsequent intermediate nodes prior to the actual data burst’s arrival. In that way, the data burst will fly-by each node and hence no requirement for temporary buffering at all in-termediate nodes. An operational requirement of an OBS network is that it be loss-less as in that way a consistent as well as acceptable quality of service (QoS) for all applications and services it serves as a platform can be guaranteed. Losses in such a network are mainly caused by improper provisioning as well as dimensioning of re-sources thus leading to contentions among bursts and consequently discarding of some of the contending data bursts. Key to both pro-visioning as well as proper dimensioning of the available resources in an optimized way is the implementation of effective routing and wavelength (RWA) that will seclude any data losses due to conten-tion occurrences. On the basis of the effects of the streamline effect (SLE), that is, effectively secluding primary contention among flows (streams) in the network, we propose in this paper a limited intermediate buffering that couples with SLE aware prioritized RWA (LIB-PRWA) scheme that combats secondary contention as well. The scheme makes routing decisions such as selection of pri-mary and deflection routes based on current resources states in the candidate paths. A performance comparison of the proposed scheme is carried out and simulation results demonstrate its com-parative abilities to effectively reduce losses as well as maintaining both high network resources utilization as well as QoS.