Faculty of Engineering and Built Environment
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Item A node-regulated deflection routing framework for contention minimization(Hindawi Limited, 2020-06-08) Nleya, Bakhe; Mutsvangwa, AndrewOptical Burst Switching (OBS) paradigm coupled with Dense Wavelength Division Multiplexing (DWDM) has become a practical candidate solution for the next-generation optical backbone networks. In its practical deployment only the edge nodes are provisioned with buffering capabilities, whereas all interior (core) nodes remain buffer-less. In that way the implementation becomes quite simple as well as cost effective as there will be no need for optical buffers in the interior. However, the buffer-less nature of the interior nodes makes such networks prone to data burst contention occurrences that lead to a degradation in overall network performance as a result of sporadic heavy burst losses. Such drawbacks can be partly countered by appropriately dimensioning available network resources and reactively by way of deflecting excess as well as contending data bursts to available least-cost alternate paths. However, the deflected data bursts (traffic) must not cause network performance degradations in the deflection routes. Because minimizing contention occurrences is key to provisioning a consistent Quality of Service (QoS), we therefore in this paper propose and analyze a framework (scheme) that seeks to intelligently deflect traffic in the core network such that QoS degradations caused by contention occurrences are minimized. This is by way of regulated deflection routing (rDr) in which neural network agents are utilized in reinforcing the deflection route choices at core nodes. The framework primarily relies on both reactive and proactive regulated deflection routing approaches in order to prevent or resolve data burst contentions. Simulation results show that the scheme does effectively improve overall network performance when compared with existing contention resolution approaches. Notably, the scheme minimizes burst losses, end-to-end delays, frequency of contention occurrences, and burst deflections.Item Services and applications security in IoT enabled networks(IEEE, 2018-12) Khumalo, Zephaniah Philani; Nleya, Bakhe; Gomba, Ndadzibaya Masimba; Mutsvangwa, Andrew5G wireless together with optical backbone networks are expected to be the main pillars of the envisaged next /future generation networking (N/FGN) infrastructures. This is an impetus to practical realization of an IoT network that will support and ensure relatively higher bandwidth as well as enhanced quality of service (QoS) in both access and core network sections. The high-speed wireless links at the network peripherals will serve as a conducive platform for device-to-device (D2D) communication. D2D driven applications and services can only be effective as well as secure assuming the associated machine type communication devices (MTCDs) have been successfully verified and authenticated. Typically, D2D type services and applications involve the interaction of several MTCDs in a group. As such, secure and effective D2D group-based authentication and key agreement (AKA) protocols are necessary. They need to inherently achieve efficacy in maintaining the group key unlink-ability as well as generate minimal signalling overheads that otherwise may lead to network congestion. In this paper we detail a secure and efficient Group AKA (Gr-AKA) protocol for D2D communication. Its performance is compared to that of existing similar protocols and is found to comparably lower both computational as well as signalling overhead requirements. Overall the analysis shows that the Gr-AKA protocol improves performance in terms of fulfilling D2D communication's security requirements.Item Energy-aware lightpath routing algorithm for optical transport networks(TELKOM, 2019-09-01) Gomba, Ndadzibaya Masimba; Nleya, Bakhe; Dewa, Mendon; Mutsvangwa, Andrew; Khumalo, Zephaniah PhilaniCurrent as well as future applications and services are characterized by bandwidth intensiveness and as such are directly driving the need for the deployment as well as operation of backbone networks that optimize on bandwidth provisioning. Since infrastructural hardware equipment requirements are trebling every two years because of continued surging bandwidth demands, the telecommunication industry is also a growing direct contributor to worldwide greenhouse gases (GHG) emissions as well as energy consumption. This is driving necessities to research on more energy efficient networking approaches. A novel optimized energy-aware lightpath routing (OEA-LR) algorithm is herein proposed. It primarily takes into account the effects of physical layer impairments (PLI) since their effects in high capacity translucent optical networks may not be ignored when formulating routing and wavelength assignment (RWA) algorithms. We assume an all-optical network hence connection requests from source to destination are entirely provisioned in the optical domain, thus optical-electrical-optical (OEO) conversions are not utilised. Both analytical and simulation results indicate that the proposed algorithm improves both energy efficiency operation as well as resource utilization of the network. We further conclude on a general observation of reciprocations between energy savings and blocking performance.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 Enhanced congestion management for minimizing network performance degradation in OBS networks(Institute of Electrical and Electronics Engineers (IEEE), 2018-03) Nleya, Bakhe; Mutsvangwa, AndrewSocieta Editrice il Mulino. All rights reserved. Current global data traffic is increasingly dominated by delay and loss intolerant IP traffic which generally displays a structural self-similarity. This has necessitated the introduction of optical burst switching (OBS) as a supporting optical backbone network switching technology. Due to the buffer-less nature of optical burst switched (OBS) networks, contention/congestion in the core network can quickly lead to degradation in overall network performance at moderate to high traffic levels due to heavy burst loses. Several approaches have been explored to address this problem, notably measures that would minimize burstification delays, congestion, blocking at the same time enhancing end-to-end throughput as well as rational and fair utilization of the links. The aim is to achieve a consistent quality of service (QoS). Noting that congestion minimization is key to a consistent QoS provisioning, in this paper we propose a congestion management approach called enhanced congestion management (ECM) that seeks to guarantee a consistent QoS as well as rational and fair use of available links. It is primarily a service differentiation based scheme that aims at congestion, blocking and latency minimization, by way of combining time averaged delay segmented burstification as well as random shortest path selection based deflection routing and wavelength assignment. Simulation results show that ECM can effectively minimise congestion and at the same time improve both throughput and effective utilization, under moderate to high network traffic conditions. Overall, we show that the approach guarantees a consistent QoS.Item Quality of transmsision aware routing and wavelength assignment algorithm for blocking minimization in translucent optical networks(IEEE, 2020-08) Khumalo, Philani; Nleya, Bakhe; Mutsvangwa, Andrew; Chidzonga, RichardIn Optical Transport networks, the optical reach is defined as the maximum distance (number of hops) a lightpath connection can span before the intelligence of the sig-nal it is carrying to unrecoverable state as a result of the degra-dation in the signal to noise power ratios. When the signal to noise ratio has degraded below a certain acceptable threshold, regeneration is necessary. Optical Transport networks will nor-mally incorporate optical repeaters throughout to facilitate sig-nal reach for all the lightpath connection establishments. Such networks are classified as being Translucent. The role of the sparsely spaced optical repeaters is to refresh the degraded op-tical signals so that an acceptable quality of transmission (QoT) can be guaranteed by the network operator. The deployment of such units where necessary throughout the network leads to an escalation to both capital as well as operational expenditures. It is however necessary that network designers strike a balance be-tween the network operating costs versus renderable quality of service (QoS) to end users. In light of this challenge, in this pa-per we propose and analyze a QoT-Aware routing and wave-length assignment algorithm (QARWA) that seeks to minimize blocking of data bursts traversing the network. The QoT block-ing considers the effects of various linear as well as nonlinear impairments. The proposed model can be infused with other al-gorithms that attempt to calculate wavelength blocking per route and also per available layer. We also further enhance the same algorithm’s efficacy by introducing its QoT aware guar-anteed RWA (QGRWA) equivalent. The novelty of the scheme is in taking into account physical layer impairments, as well as signal quality when computing candidate routes for a given source to destination pair. The proposed algorithm’s overall promising performance is validated via analytical and simula-tion means.Item Evaluation of wavelength congestion in transparent optical transport networks(IEEE, 2020-08) Gomba, Ndadzibaya Masimba; Nleya, Bakhe; Mutsvangwa, Andrew; Chidzonga, Richard F.Transparent Optical networks are generally regarded as a possible solution for the provisioning of ultrahigh speed transmission and switching capabilities to accommodate bandwidth hungry applications and services. Most of such applications and services involve streaming of high-definition video. However, since al source and destination pair establishments within a given Transparent optical transport network are assumed to be within optical signal reach, such networks do not incorporate regenerators. The lack of regenerators often leads to a serious degradation of the signal to noise ratio as a result of the effects of physical layer impairments accumulated as it traverses the network. This motivates us to propose and present a Q-factor tool that takes into account the various physical layer impairments. The proposed tool’s efficacy is evaluated by way of simulation.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 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.