On QoS-assured degraded provisioning in service-differentiated multi-layer elastic optical networks

The emergence of new network applications is driving network operators to not only fulfill dynamic bandwidth requirements, but offer various grades of service. Degraded provisioning provides an effective solution to flexibly allocate resources in various dimensions to reduce blocking for differentiated demands when network congestion occurs. In this work, we investigate the novel problem of online degraded provisioning in service-differentiated multi-layer networks with optical elasticity. Quality of Service (QoS) is assured by service-holding-time prolongation and immediate access as soon as the service arrives without set-up delay. We decompose the problem into degraded routing and degraded resource allocation stages, and design polynomial-time algorithms with the enhanced multi-layer architecture to increase the network flexibility in temporal and spectral dimensions. Illustrative results verify that we can achieve significant reduction of network service failures, especially for requests with higher priorities. The results also indicate that degradation in optical layer can increase the network capacity, while the degradation in electric layer provides flexible time-bandwidth exchange.Comment: accepted by IEEE GLOBECOM 201

Exploiting the power of multiplicity: a holistic survey of network-layer multipath

The Internet is inherently a multipath network: For an underlying network with only a single path, connecting various nodes would have been debilitatingly fragile. Unfortunately, traditional Internet technologies have been designed around the restrictive assumption of a single working path between a source and a destination. The lack of native multipath support constrains network performance even as the underlying network is richly connected and has redundant multiple paths. Computer networks can exploit the power of multiplicity, through which a diverse collection of paths is resource pooled as a single resource, to unlock the inherent redundancy of the Internet. This opens up a new vista of opportunities, promising increased throughput (through concurrent usage of multiple paths) and increased reliability and fault tolerance (through the use of multiple paths in backup/redundant arrangements). There are many emerging trends in networking that signify that the Internet's future will be multipath, including the use of multipath technology in data center computing; the ready availability of multiple heterogeneous radio interfaces in wireless (such as Wi-Fi and cellular) in wireless devices; ubiquity of mobile devices that are multihomed with heterogeneous access networks; and the development and standardization of multipath transport protocols such as multipath TCP. The aim of this paper is to provide a comprehensive survey of the literature on network-layer multipath solutions. We will present a detailed investigation of two important design issues, namely, the control plane problem of how to compute and select the routes and the data plane problem of how to split the flow on the computed paths. The main contribution of this paper is a systematic articulation of the main design issues in network-layer multipath routing along with a broad-ranging survey of the vast literature on network-layer multipathing. We also highlight open issues and identify directions for future work

Topology overlays for dedicated protection Ethernet LAN services in advanced SONET/SDH networks

The explosion of information technology (IT) services coupled with much-increased personal and scientific computing capabilities has resulted in great demand for more scalable and reliable networking services. Along these lines, carriers have spent large sums to transition their legacy\u27 SONET/SDH voice-based networking infrastructures to better support client-side Ethernet data interfaces, i.e., next-generation SONET/SDH (NGS). In particular, a key addition here has been the new virtual concatenation (VCAT) feature which supports inverse multiplexing to \u27split\u27 larger connection requests in to a series of independently-routed \u27sub-connections\u27. As these improved infrastructures have been deployed, the design of new Ethernet over SONET/SDH (EoS) services has become a key focus area for carriers, i.e., including point-to-point and multi-point services. In light of the above, this thesis focuses on the study of improved multi-point EoS schemes in NGS networks, i.e., to provision robust \u27virtual LAN\u27 capabilities over metro and wide-area domains. Indeed, as services demands grow, survivability considerations are becoming a key concern. Along these lines, the proposed solution develops novel multi-tiered (partial) protection strategies. Specifically, graph-theoretic algorithms are first proposed to interconnect multi-point node groups using bus and minimum spanning tree (MST) overlays. Next, advanced multi-path routing schemes are used to provision and protect these individual overlay connections using the inverse-multiplexing capabilities of NGS. Finally, post-fault restoration features are also added to handle expanded failure conditions, e.g., multiple failures. The performances of the proposed multi-point EoS algorithms developed in this research are gauged using advanced software-based simulation in the OPNET ModelerTM environment. The findings indicate that both the bus and MST overlays give very good performance in terms of request blocking and carried load. However, the MST-based overlays slightly outperform the bus-based overlays as they allow more efficient topology designs. In addition, the incorporation of dynamic load state information in the selection of bus and/or MST overlays is also very beneficial as opposed to just using static hop count state. Furthermore, inverse-multiplexing is highly-effective, yielding notably higher carried loads when coupled with load-balancing sub-connection routing. Finally, results also show that post-fault restoration is also a very effective means of boosting EoS LAN throughputs for partially-protected demands, consistently matching the reliability of full-protection setups.\u2

Simple and stable dynamic traffic engineering for provider scale ethernet

Trabalho apresentado no âmbito do Mestrado em Engenharia Informática, como requisito parcial para obtenção do grau de Mestre em Engenharia InformáticaThe high speeds and decreasing costs of Ethernet solutions has motivated providers’ interest in using Ethernet as the link layer technology in their backbone and aggregation networks. Provider scale Ethernet offers further advantages, providing not only an easy to manage solution for multicast traffic, but also transparent interconnection between clients’ LANs. These Ethernet deployments face altogether different design issues, requiring support for a significantly higher number of hosts. This support relies on hierarquization, separating address and virtual network spaces of customers and providers. In addition, large scale Ethernet solutions need to grant forwarding optimality. This can be achieved using traffic engineering approaches. Traffic engineering defines the set of engineering methods and techniques used to optimize the flow of network traffic. Static traffic engineering approaches enjoy widespread use in provider networks, but their performance is greatly penalized by sudden load variations. On the other hand, dynamic traffic engineering is tailored to adapt to load changes. However, providers are skeptical to adopt dynamic approaches as these induce problems such as routing instability, and as a result, network performance decreases. This dissertation presents a Simple and Stable Dynamic Traffic Engineering framework (SSD-TE), which addresses these concerns in a provider scale Ethernet scenario. The validation results show that SSD-TE achieves better or equal performance to static traffic engineering approaches, whilst remaining both stable and responsive to load variations