| 14411. |
- Hernandez Benet, Cristian, et al.
(författare)
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SDN implementations and protocols
- 2018. - 1
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Ingår i: Big Data and Software Defined Networks. - : IET Digital Library. - 9781785613043 - 9781785613050 ; , s. 27-48
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Bokkapitel (refereegranskat)abstract
- This chapter begins by explaining the main SDN concepts with the focus on a SDN controller. It presents the most important aspects to consider when we desire to go from traditional network to a SDN networks. We present an in-depth analysis of the most commonly used and modern SDN controllers and analyse the main features, capabilities and requirements of one of the presented controllers. OpenFlow is the standard leading in the market allowing the management of the forwarding plane devices such as routers or switches. While there are other standards with the same aim, OpenFlow has secured a position in the market and has been expanded rapidly. Therefore, an analysis is presented on a different OpenFlow compatible device for the implementation of an SDN network. This study encompasses both software and hardware solutions along with the scope of implementation or use of these devices. This chapter ends up presenting a description of OpenFlow protocol alternatives, a more detailed description of OpenFlow and its components and other wellknown southbound protocols involved for the management and configuration of the devices.
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| 14412. |
- Hernandez Benet, Cristian
(författare)
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Traffic Management in Software-Defined Data Center Networks
- 2021
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Traffic management in data centers is paramount to improving network and application performance, thereby improving the quality of service by reducing network congestion, packet loss, and latency. However, the deployment and configuration of traffic management techniques are challenging due to diverse data-center traffic characteristics, large data center topologies, and the interplay of different protocols at the routing, transport, and link layer. Software-Defined Networking (SDN) emerges as a new paradigm towards a centralized network configuration and traffic management by decoupling the control plane from forwarding devices. Despite its holistic view of the network, data centers are commonly interconnected by traditional networks that use standard routing protocols. It is therefore essential to achieve interoperability with legacy systems, end-to-end traffic management, and to avoid the cumbersome, time-consuming, and error-prone configuration process of data-center edge network devices.In this thesis, we aim to improve traffic management and its configuration for software-defined data center networks. To achieve this objective, we provide novel approaches that enhance the control plane as well as leverage novel concepts of data plane programmability.At the control plane, we first propose different mechanisms that enable the fast restoration of network connectivity after a virtual machine migration. Second, we suggest a network management automation framework that extends layer 2 connectivity to the tenants' services hosted across geo-distributed data centers. Moreover, we provide high-level policy-based mechanisms that make network configuration and traffic management simpler for data-center operators. At the data plane, we develop MP-HULA that load-balances multipath connections across least-congested paths. MP-HULA leverages advanced data plane mechanisms to rank multiple paths according to congestion metrics and uses that information for fine-grained load-balancing decisions considering transport layer information. To improve flowlet-based load-balancing decisions, we propose FlowDyn, which efficiently estimates round-trip time using programmable telemetry data. Finally, we present pCoflow, an in-network support mechanism that uses advanced programmable scheduling primitives to effectively avoid reordering for data-parallel applications even when there are flow priority changes due to global coflow scheduling updates.
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| 14413. |
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| 14414. |
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| 14415. |
- Herold, Sebastian
(författare)
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An initial study on the association between architectural smells and degradation
- 2020
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Ingår i: Software Architecture. ECSA 2020.. - Cham : Springer. - 9783030589233 - 9783030589226 ; , s. 193-201
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Konferensbidrag (refereegranskat)abstract
- It is generally assumed that architectural smells are associated with software architectural degradation. Treating smells could hence help treating degradation. This article investigates the association between three types of architectural smells and the existence of architecture-violating dependencies as manifestation of architectural degradation in software.We gathered data about architectural smells and violations from a single system with a validated prescriptive architecture. The data was analysed to identify and characterise associations between architectural smells and violations. Statistically relevant associations were identified for two of three smells, namely cyclic dependencies and unstable dependencies. Effect sizes were small for both though.These results provide evidence for cyclic and unstable dependencies having a larger risk of including architectural violations. The small effect sizes indicate that the presence of architectural smells cannot explain architectural degradation alone. This shows that complementing methods and techniques are required for exhaustive treatment of both phenomena.
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| 14416. |
- Herold, Sebastian
(författare)
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Architectural Compliance in Component-Based Systems : Foundations, Specification, and Checking of Architectural Rules
- 2011
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- The intended software architecture of a software system manifests the earliest and most fundamental design decisions. To ensure that the final software product is consistent with those design decisions and the requirements realized that way, the software architecture has to be refined correctly. This means that the artefacts of detailed design and implementation have to comply with the intended software architecture.A basic task to ensure architectural compliance is the checking of architectural rules. These rules are constraints resulting from the application of architectural principles, like patterns, reference architectures or guidelines, and restricting the way an architecture can be refined. However, checking those rules is difficult. Manual checks are in general not possible due to the size and complexity of modern software systems. But realizing powerful tool support is challenging, since compliance checking tools have to be very flexible regarding the great variety of architectural rules and the number of artefact types requiring compliance checking.This thesis develops an approach to flexible architecture compliance checking in model-based development approaches for component-based systems.It describes a conceptual framework, in which models are interpreted as first-order logic statements about component-based systems; architectural rules as fundamental parts of architectural models, are logical statements, too. Compliance between models can be expressed this way as semantically-founded relation between logical formulae.The developed concepts are evaluated by a case study system following several different architectural principles. Architectural rules are developed for those principles and are checked for compliance. Furthermore, a prototypical compliance checking tool basing upon a logic-based knowledge representation and reasoning system is realized.Both, the conceptual framework as well as the prototypical implementation, allow very flexible architectural compliance checking. Due to the developed formalization, a broad range of architectural rules can be specified, largely meta model-independently. Aside from the significant improvement of tool support compared with the state of the art, the approach fosters furthermore a new understanding of the role of software architecture; as blue-print for design and implementation, the need for explicitly modelled architectural rules is emphasized.
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| 14417. |
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| 14418. |
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| 14419. |
- Herold, Sebastian, et al.
(författare)
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CoCoME - The Common Component Modeling Example
- 2008
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Ingår i: The Common Component Modeling Example. - Berlin, Heidelberg : Springer. - 9783540852889 ; , s. 16-53
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Bokkapitel (övrigt vetenskapligt/konstnärligt)
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| 14420. |
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