Faculty of Engineering and Built Environment
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Item 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, MasimbaAll 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 utilizationItem A RWA framework for improved throughput in OBS networks(Springer Science and Business Media LLC, 2021-08) Nleya, BakheAll-Optical Burst Switched (OBS) backbone transport networks facilitate connectionless transport utilizing wavelength division multiplexing of multiple lightpaths end-to-end channels. The data in such networks is transmitted in the form of bursts. However, whereas such networks provide capacities in the Terahertz ranges, the data bursts being ferried often contend with each other at intermediate (interior) buffer-less nodes. The frequent occurrences of both contentions, as well as wavelength congestions, are often characterized by degradations in overall network performance in handling moderate to high traffic levels, and all this is attributed to increases in burst losses. Whereas deflection routing contention resolution is quite popular in combating both contention and wavelength congestions to improve overall network throughput, it is however necessary that network throughput always balances with effective utilization. Further complexity is that of most practical backbone transport networks often being multi-domain in nature and thus necessitating the dimensioning of deflection routing resources for both interdomain and intra-domain traffic to avoid degradation of network performance in terms of contention as well as wavelength congestion occurrences in one domain due to improper dimensioning in the other(s). In this regard, a combination of appropriately designating border nodes and grooming interdomain traffic will vastly improve overall network performance as well as fairness to multiple domain lightpath connections. In this paper, we propose a prioritized (indexed) cooperativebased routing and wavelength assignment (PIC-RWA) scheme that couples with wavelength grooming for inter-border traffic to reduce both contention and wavelength congestions. Performance results indicate that it significantly improves overall network performance in terms of improved effective resources utilization.Item A limited intermediate node buffering based RWA scheme in OBS backbone networks(Ponte Academic Journal, 2019-11) Nleya, Bakhe; Mutsvangwa, AndrewAn 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.Item 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.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.