Concurrent multipath transmission to improve performance for multi-homed devices in heterogeneous networks

Recent network technology developments have led to the emergence of a variety of access network technologies - such as IEEE 802.11, wireless local area network (WLAN), IEEE 802.16, Worldwide Interoperability for Microwave Access (WIMAX) and Long Term Evolution (LTE) - which can be integrated to offer ubiquitous access in a heterogeneous network environment. User devices also come equipped with multiple network interfaces to connect to the different network technologies, making it possible to establish multiple network paths between end hosts. However, the current connectivity settings confine the user devices to using a single network path at a time, leading to low utilization of the resources in a heterogeneous network and poor performance for demanding applications, such as high definition video streaming. The simultaneous use of multiple network interfaces, also called bandwidth aggregation, can increase application throughput and reduce the packets' end-to-end delays. However, multiple independent paths often have heterogeneous characteristics in terms of offered bandwidth, latency and loss rate, making it challenging to achieve efficient bandwidth aggregation. For instance, striping the flow's packets over multiple network paths with different latencies can cause packet reordering, which can significantly degrade performance of the current transport protocols. This thesis proposes three new solutions to mitigate the effects of network path heterogeneity on the performance of various concurrent multipath transmission settings. First, a network layer solution is proposed to stripe packets of delay-sensitive and high-bandwidth applications for concurrent transmission across multiple network paths. The solution leverages the paths' latency heterogeneity to reduce packet reordering, leading to minimal reordering delay, which improves performance of delay-sensitive applications. Second, multipath video streaming is developed for H.264 scalable video, where the reference video packets are adaptively assigned to low loss network paths to reduce drifting errors, thus combatting H.264 video distortion effectively. Finally, a new segment scheduling framework - which carefully considers path heterogeneity - is incorporated into the IETF Multipath TCP to improve throughput performance. The proposed solutions have been validated using a series of simulation experiments. The results reveal that the proposed solutions can enable efficient bandwidth aggregation for concurrent multipath transmission over heterogeneous network paths

Multistage Packet-Switching Fabrics for Data Center Networks

Recent applications have imposed stringent requirements within the Data Center Network (DCN) switches in terms of scalability, throughput and latency. In this thesis, the architectural design of the packet-switches is tackled in different ways to enable the expansion in both the number of connected endpoints and traffic volume. A cost-effective Clos-network switch with partially buffered units is proposed and two packet scheduling algorithms are described. The first algorithm adopts many simple and distributed arbiters, while the second approach relies on a central arbiter to guarantee an ordered packet delivery. For an improved scalability, the Clos switch is build using a Network-on-Chip (NoC) fabric instead of the common crossbar units. The Clos-UDN architecture made with Input-Queued (IQ) Uni-Directional NoC modules (UDNs) simplifies the input line cards and obviates the need for the costly Virtual Output Queues (VOQs). It also avoids the need for complex, and synchronized scheduling processes, and offers speedup, load balancing, and good path diversity. Under skewed traffic, a reliable micro load-balancing contributes to boosting the overall network performance. Taking advantage of the NoC paradigm, a wrapped-around multistage switch with fully interconnected Central Modules (CMs) is proposed. The architecture operates with a congestion-aware routing algorithm that proactively distributes the traffic load across the switching modules, and enhances the switch performance under critical packet arrivals. The implementation of small on-chip buffers has been made perfectly feasible using the current technology. This motivated the implementation of a large switching architecture with an Output-Queued (OQ) NoC fabric. The design merges assets of the output queuing, and NoCs to provide high throughput, and smooth latency variations. An approximate analytical model of the switch performance is also proposed. To further exploit the potential of the NoC fabrics and their modularity features, a high capacity Clos switch with Multi-Directional NoC (MDN) modules is presented. The Clos-MDN switching architecture exhibits a more compact layout than the Clos-UDN switch. It scales better and faster in port count and traffic load. Results achieved in this thesis demonstrate the high performance, expandability and programmability features of the proposed packet-switches which makes them promising candidates for the next-generation data center networking infrastructure

Multistage Packet-Switching Fabrics for Data Center Networks

Recent applications have imposed stringent requirements within the Data Center Network (DCN) switches in terms of scalability, throughput and latency. In this thesis, the architectural design of the packet-switches is tackled in different ways to enable the expansion in both the number of connected endpoints and traffic volume. A cost-effective Clos-network switch with partially buffered units is proposed and two packet scheduling algorithms are described. The first algorithm adopts many simple and distributed arbiters, while the second approach relies on a central arbiter to guarantee an ordered packet delivery. For an improved scalability, the Clos switch is build using a Network-on-Chip (NoC) fabric instead of the common crossbar units. The Clos-UDN architecture made with Input-Queued (IQ) Uni-Directional NoC modules (UDNs) simplifies the input line cards and obviates the need for the costly Virtual Output Queues (VOQs). It also avoids the need for complex, and synchronized scheduling processes, and offers speedup, load balancing, and good path diversity. Under skewed traffic, a reliable micro load-balancing contributes to boosting the overall network performance. Taking advantage of the NoC paradigm, a wrapped-around multistage switch with fully interconnected Central Modules (CMs) is proposed. The architecture operates with a congestion-aware routing algorithm that proactively distributes the traffic load across the switching modules, and enhances the switch performance under critical packet arrivals. The implementation of small on-chip buffers has been made perfectly feasible using the current technology. This motivated the implementation of a large switching architecture with an Output-Queued (OQ) NoC fabric. The design merges assets of the output queuing, and NoCs to provide high throughput, and smooth latency variations. An approximate analytical model of the switch performance is also proposed. To further exploit the potential of the NoC fabrics and their modularity features, a high capacity Clos switch with Multi-Directional NoC (MDN) modules is presented. The Clos-MDN switching architecture exhibits a more compact layout than the Clos-UDN switch. It scales better and faster in port count and traffic load. Results achieved in this thesis demonstrate the high performance, expandability and programmability features of the proposed packet-switches which makes them promising candidates for the next-generation data center networking infrastructure

Host and Network Optimizations for Performance Enhancement and Energy Efficiency in Data Center Networks

Modern data centers host hundreds of thousands of servers to achieve economies of scale. Such a huge number of servers create challenges for the data center network (DCN) to provide proportionally large bandwidth. In addition, the deployment of virtual machines (VMs) in data centers raises the requirements for efficient resource allocation and find-grained resource sharing. Further, the large number of servers and switches in the data center consume significant amounts of energy. Even though servers become more energy efficient with various energy saving techniques, DCN still accounts for 20% to 50% of the energy consumed by the entire data center. The objective of this dissertation is to enhance DCN performance as well as its energy efficiency by conducting optimizations on both host and network sides. First, as the DCN demands huge bisection bandwidth to interconnect all the servers, we propose a parallel packet switch (PPS) architecture that directly processes variable length packets without segmentation-and-reassembly (SAR). The proposed PPS achieves large bandwidth by combining switching capacities of multiple fabrics, and it further improves the switch throughput by avoiding padding bits in SAR. Second, since certain resource demands of the VM are bursty and demonstrate stochastic nature, to satisfy both deterministic and stochastic demands in VM placement, we propose the Max-Min Multidimensional Stochastic Bin Packing (M3SBP) algorithm. M3SBP calculates an equivalent deterministic value for the stochastic demands, and maximizes the minimum resource utilization ratio of each server. Third, to provide necessary traffic isolation for VMs that share the same physical network adapter, we propose the Flow-level Bandwidth Provisioning (FBP) algorithm. By reducing the flow scheduling problem to multiple stages of packet queuing problems, FBP guarantees the provisioned bandwidth and delay performance for each flow. Finally, while DCNs are typically provisioned with full bisection bandwidth, DCN traffic demonstrates fluctuating patterns, we propose a joint host-network optimization scheme to enhance the energy efficiency of DCNs during off-peak traffic hours. The proposed scheme utilizes a unified representation method that converts the VM placement problem to a routing problem and employs depth-first and best-fit search to find efficient paths for flows

Novel applications and contexts for the cognitive packet network

Autonomic communication, which is the development of self-configuring, self-adapting, self-optimising and self-healing communication systems, has gained much attention in the network research community. This can be explained by the increasing demand for more sophisticated networking technologies with physical realities that possess computation capabilities and can operate successfully with minimum human intervention. Such systems are driving innovative applications and services that improve the quality of life of citizens both socially and economically. Furthermore, autonomic communication, because of its decentralised approach to communication, is also being explored by the research community as an alternative to centralised control infrastructures for efficient management of large networks. This thesis studies one of the successful contributions in the autonomic communication research, the Cognitive Packet Network (CPN). CPN is a highly scalable adaptive routing protocol that allows for decentralised control in communication. Consequently, CPN has achieved significant successes, and because of the direction of research, we expect it to continue to find relevance. To investigate this hypothesis, we research new applications and contexts for CPN. This thesis first studies Information-Centric Networking (ICN), a future Internet architecture proposal. ICN adopts a data-centric approach such that contents are directly addressable at the network level and in-network caching is easily supported. An optimal caching strategy for an information-centric network is first analysed, and approximate solutions are developed and evaluated. Furthermore, a CPN inspired forwarding strategy for directing requests in such a way that exploits the in-network caching capability of ICN is proposed. The proposed strategy is evaluated via discrete event simulations and shown to be more effective in its search for local cache hits compared to the conventional methods. Finally, CPN is proposed to implement the routing system of an Emergency Cyber-Physical System for guiding evacuees in confined spaces in emergency situations. By exploiting CPN’s QoS capabilities, different paths are assigned to evacuees based on their ongoing health conditions using well-defined path metrics. The proposed system is evaluated via discrete-event simulations and shown to improve survival chances compared to a static system that treats evacuees in the same way.Open Acces

Journal of Telecommunications and Information Technology, 2018, nr 1

kwartalni

The Virtual Bus: A Network Architecture Designed to Support Modular-Redundant Distributed Periodic Real-Time Control Systems

The Virtual Bus network architecture uses physical layer switching and a combination of space- and time-division multiplexing to link segments of a partial mesh network together on schedule to temporarily form contention-free multi-hop, multi-drop simplex signalling paths, or 'virtual buses'. Network resources are scheduled and routed by a dynamic distributed resource allocation mechanism with self-forming and self-healing characteristics. Multiple virtual buses can coexist simultaneously in a single network, as the resources allocated to each bus are orthogonal in either space or time. The Virtual Bus architecture achieves deterministic delivery times for time-sensitive traffic over multi-hop partial mesh networks by employing true line-speed switching; delays of around 15ns at each switching point are demonstrated experimentally, and further reductions in switching delays are shown to be achievable. Virtual buses are inherently multicast, with delivery skew across multiple destinations proportional to the difference in equivalent physical length to each destination. The Virtual Bus architecture is not a purely theoretical concept; a small research platform has been constructed for development, testing and demonstration purposes

A business process reengineering framework using the analytic hierarchy process to select a traceability technology for spare parts management in capital-intensive industries

Thesis (MEng)--Stellenbosch University, 2016.ENGLISH ABSTRACT: demand forecasting for spare parts; and inventory warehousing management. Various aspects (including 29 best practices) of BPR are described in order to support the proposed framework. These include criteria for selecting processes to redesign, the role of Information Technology in BPR and typical barriers to eff ective implementation of BPR. The AHP (a multi-criteria decision-making method) is explained in detail, as it facilitates the selection of asset traceability technology. An overview of asset traceability technologies (speci fically barcode technology, Radio Frequency Identi cation (RFID) technology and Global Positioning System (GPS) technology) is also provided, including the description of certain characteristics of each technology. The proposed framework, based on the literature review, serves as a structured guide and consists of two primary parallel elements (referred to as streams), namely the BPR stream and the Change Management stream. The BPR stream encompasses six phases of BPR (Contextualise SPM, Business Process Redesign, Asset Traceability Technology, Decision-Making, Implement, and Monitor and Evaluate) while the Change Management stream consists of three stages (Unfreeze State, Change State and Refreeze State). The framework is validated through face validation via semi-structured interviews with participants forming a panel of experts involved in and familiar with SPM and asset traceability technology. According to the expert panel, the proposed framework satisfies achievement of the desired framework attributes, namely (i) Generic and adaptable, (ii) Holistic and comprehensive, (iii) Structured and objective- or outcome-oriented and (iv) Practical. In addition, the expert panel perceived the framework to be useful, easy to use and understandable. However, recommendations were proposed to further improve the framework, including the addition of a scoping and objectives section and the expansion of the Change Management element.AFRIKAANSE OPSOMMING: Onderdele is noodsaaklik vir die e ektiewe bedryf van 'n kapitaal-intensiewe organisasie en maak, tesame met materiaalverbruik, ongeveer 50% uit van 'n tipiese instandhoudingsbegroting. Ten spyte van die relatief groot hoeveelheid literatuur beskikbaar oor onderdele, pas min maatskappye egter ordentlike strukturele, feitlike en kwantitatiewe Onderdelebestuur toe. Geïntegreerde benaderings om onderdele te bestuur, sowel as om teoretiese modelle te ondersteun met praktiese riglyne, word benodig ten einde die gaping tussen navorsing en praktyk te oorbrug. Die studie het voortgevloei uit 'n geleentheid geïdenti seer om prosesse binne Onderdelebestuur te verbeter, spesi ek deur die gebruik van bate opspoorbaarheidstegnologie. 'n Raamwerk word voorgestel wat (i) die Besigheidsproses Hersiening lei deur prosesse binne Onderdelebestuur, met die inagneming van elemente van Veranderingsbestuur, en (ii) die keuse van opspoorbaarheidstegnologie lei vir integrasie binne Onderdelebestuur by kapitaal-intensiewe organisasies (deur die gebruik van die Analitiese Hiërargie Proses). Die navorsing bestaan uit 'n bespreking van Batebestuur, insluitend PAS 55 en ISO 55000 (twee belangrike Batebestuur dokumentreekse) en Veranderings-bestuur, wat 'n noodsaaklike aspek vir implementering is. Vervolgens word Onderdelebestuur, 'n onderafdeling van Batebestuur wat verband hou met onderdele en die fokuspunt van die studie is, aangespreek. Die volgende Onderdelebestuur aspekte word onder andere aangespreek: eienskappe van onderdele en hoe onderdele van ander algemene voorraad verskil; klassi seringskriteria en klassi seringstegnieke; vooruitskatting van die vraag na onderdele; en die bestuur van voorraadvlakke. Verskeie aspekte (insluitend 29 beste praktyke) van Besigheidsproses Hersiening word beskryf ten einde die voorgestelde raamwerk te ondersteun. Dit sluit kriteria in vir die keuse van herontwerpsprosesse, die rol van Inligtingstegnologie in Besigheidsproses Hersiening en tipiese struikelblokke vir die e ektiewe implementering van Besigheidsproses Hersiening. Die Analitiese Hiërargie Proses ('n multi-kriteria besluitnemingsmetode) word in detail verduidelik, aangesien dit die keuse van 'n bate opspoorbaarheidstegnolgie moet fasiliteer. 'n Oorsig van bate pspoorbaarheidstegnolgieë (spesi ek strepieskode tegnologie, Radiofrekwensie Identi kasie (RFID) tegnologie en Globale Posisioneringstelsel (GPS) tegnologie) word ook verskaf, insluitend die beskrywing van sekere eienskappe van elke tegnolgie. Die voorgestelde raamwerk, gebasseer op die literatuurstudie, dien as 'n gestruktureerde gids en bestaan uit twee primêre parallele elemente (wat na verwys word as strome), naamlik die Besigheidsproses Hersiening stroom en die Veranderingsbestuur stroom. Die Besigheidsproses Hersiening stroom vervat ses fases van Besigheidsproses Hersiening (Kontekstualiseer Onderdelebestuur, Besigheidsproses Hersiening, Bate Opspoorbaarheidstegnolgie, Besluitneming, Implementeer, en Monitor en Evalueer) terwyl die Veranderingsbestuur stroom bestaan uit drie stadiums (Ontvries Stadium, Verander Stadium en Hervries Stadium). Die voorgestelde raamwerk word bekragtig deur sigwaarde bekragtiging via semi-gestruktureerde onderhoude met deelnemers wat 'n paneel van deskundiges vorm wat betrokke en vertroud is met Onderdelebestuur en Bate Opspoorbaarheidstegnolgie. Volgens die paneel van deskundiges slaag die voorgestelde raamwerk daarin om die vereiste raamwerk kenmerke te bereik, naamlik (i) Generies en aanpasbaar, (ii) Holisties en omvattend, (iii) Gestruktureerd en doelof uitkomsgeöriënteerd en (iv) Prakties. Boonop het die paneel van deskundiges die raamwerk gesien as nuttig, maklik om te gebruik en verstaanbaar. Aanbevelings was egter voorgestel om die raamwerk verder te verbeter, insluitend die byvoeging van 'n bestek en doelwitte afdeling en die uitbreiding van die Veranderingsbestuur element