Faculty of Engineering and Built Environment
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Item Intermediate node buffering-based contention minimization scheme(TELKOM, 2019-09-01) Khumalo, Philani; Nleya, Bakhe; Mutsvangwa, Andrew; Boysen, GysOptical burst switching (OBS) is a candidate switching paradigm for future backbone all-optical networks. However, data burst contention can be a major problem especially as the number of lightpath connections as well as the overall network radius increases. Furthermore, the absence of or limited buffering provision in core nodes, coupled with the standard one-way resources signalling aggravate contention occurrences resulting in some of the contending bursts being discarded. In this paper we propose and analyze a restricted intermediate Node Buffering based routing and wavelength assignment scheme (RI-RWA) scheme in which intermediate buffering provisioning is implemented for contending data bursts have already propagated more than half the network’s diameter. The aim is not to discard such bursts as they would have already utilized a considerable amount of available network resources. We comparatively evaluate the scheme’s performance in terms of performance indicators such as fairness, load balancing as well as throughput.Item 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, AndrewAbstract - 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.