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Faculty of Engineering and Built Environment

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Author: search.filters.author.Mutsvangwa, AndrewSubject: search.filters.subject.Contention

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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 controlled deflection routing and wavelength assignment based scheme in Optical Burst Switched (OBS) networks
    (Walter de Gruyter GmbH, 2020-07-05) Nleya, Bakhe; Khumalo, Zephaniah Philani; Mutsvangwa, Andrew
    Abstract - Heterogeneous IoT-enabled networks generally accommodate both jitter tolerant and intolerant traffic. Optical Burst Switched (OBS) backbone networks handle the resultant volumes of such traffic by transmitting it in huge size chunks called bursts. Because of the lack of or limited buffering capabilities within the core network, burst contentions may frequently occur and thus affect overall supportable quality of service (QoS). Burst contention(s) in the core network is generally characterized by frequent burst losses as well as differential delays especially when traffic levels surge. Burst contention can be resolved in the core network by way of partial buffering using fiber delay lines (FDLs), wavelength conversion using wavelength converters (WCs) or deflection routing. In this paper, we assume that burst contention is 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, the paper proposes a controlled deflection routing (CDR) and wavelength assignment based scheme that allows the deflection of bursts to alternate paths only after controller buffer preset thresholds are surpassed. In this way, bursts (or burst fragments) 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 as well as compare its performance to other existing approaches. Overall, both analytical and simulation results show that the proposed scheme does lower both congestion (on deflection routes) as well as jitter, thus also improving throughput as well as avoiding congestion on deflection paths.