Resilient network dimensioning for optical grid/clouds using relocation

In this paper we address the problem of dimensioning infrastructure, comprising both network and server resources, for large-scale decentralized distributed systems such as grids or clouds. We will provide an overview of our work in this area, and in particular focus on how to design the resulting grid/cloud to be resilient against network link and/or server site failures. To this end, we will exploit relocation: under failure conditions, a request may be sent to an alternate destination than the one under failure-free conditions. We will provide a comprehensive overview of related work in this area, and focus in some detail on our own most recent work. The latter comprises a case study where traffic has a known origin, but we assume a degree of freedom as to where its end up being processed, which is typically the case for e. g., grid applications of the bag-of-tasks (BoT) type or for providing cloud services. In particular, we will provide in this paper a new integer linear programming (ILP) formulation to solve the resilient grid/cloud dimensioning problem using failure-dependent backup routes. Our algorithm will simultaneously decide on server and network capacity. We find that in the anycast routing problem we address, the benefit of using failure-dependent (FD) rerouting is limited compared to failure-independent (FID) backup routing. We confirm our earlier findings in terms of network capacity savings achieved by relocation compared to not exploiting relocation (order of 6-10% in the current case studies)

Joint dimensioning of server and network infrastructure for resilient optical grids/clouds

We address the dimensioning of infrastructure, comprising both network and server resources, for large-scale decentralized distributed systems such as grids or clouds. We design the resulting grid/cloud to be resilient against network link or server failures. To this end, we exploit relocation: Under failure conditions, a grid job or cloud virtual machine may be served at an alternate destination (i.e., different from the one under failure-free conditions). We thus consider grid/cloud requests to have a known origin, but assume a degree of freedom as to where they end up being served, which is the case for grid applications of the bag-of-tasks (BoT) type or hosted virtual machines in the cloud case. We present a generic methodology based on integer linear programming (ILP) that: 1) chooses a given number of sites in a given network topology where to install server infrastructure; and 2) determines the amount of both network and server capacity to cater for both the failure-free scenario and failures of links or nodes. For the latter, we consider either failure-independent (FID) or failure-dependent (FD) recovery. Case studies on European-scale networks show that relocation allows considerable reduction of the total amount of network and server resources, especially in sparse topologies and for higher numbers of server sites. Adopting a failure-dependent backup routing strategy does lead to lower resource dimensions, but only when we adopt relocation (especially for a high number of server sites): Without exploiting relocation, potential savings of FD versus FID are not meaningful

Design and operation of mesh-restorable WDM networks

The explosive growth of Web-related services over the Internet is bringing millions of new users online, thus creating a growing demand for bandwidth. Wavelength Division Multiplexed (WDM) networks, employing wavelength routing has emerged as the dominant technology to satisfy this growing demand for bandwidth. As the amount of traffic carried is larger, any single failure can be catastrophic. Survivability becomes indispensable in such networks. Therefore, it is imperative to design networks that can quickly and efficiently recover from failures.;In this dissertation, we explore the design and operation of survivable optical networks. We study several survivability paradigms for surviving single link failures. A restoration model is developed based on a combination of these paradigms. We propose an optimal design and upgrade scheme for WDM backbone networks. We formulate an integer programming-based design problem to minimize the total facility cost. This framework provides a cost effective way of upgrading the network by identifying how much resources to budget at each stage of network evolution. This results in significant cost reductions for the network service provider.;As part of network operation, we capture multiple operational phases in survivable network operation as a single integer programming formulation. This common framework incorporates service disruption and includes a service differentiation model based on lightpath protection. However, the complexity of the optimization problem makes the formulation applicable only for network provisioning and o2ine reconfiguration. The direct use of such methods for online reconfiguration remains limited to small networks with few tens of wavelengths. We develop a heuristic algorithm based on LP relaxation technique for fast, near optimal, online reconfiguration. Since the ILP variables are relaxed, we provide a way to derive a feasible solution from the relaxed problem. Most of the current approaches assume centralized information. They do not scale well as they rely on per-flow information. This motivates the need for developing dynamic algorithms based on partial information. The partial information we use can be easily obtained from traffic engineering extensions to routing protocols. Finally, the performance of partial information routing algorithms is compared through simulation studies

Robust Energy Management for Green and Survivable IP Networks

Despite the growing necessity to make Internet greener, it is worth pointing out that energy-aware strategies to minimize network energy consumption must not undermine the normal network operation. In particular, two very important issues that may limit the application of green networking techniques concern, respectively, network survivability, i.e. the network capability to react to device failures, and robustness to traffic variations. We propose novel modelling techniques to minimize the daily energy consumption of IP networks, while explicitly guaranteeing, in addition to typical QoS requirements, both network survivability and robustness to traffic variations. The impact of such limitations on final network consumption is exhaustively investigated. Daily traffic variations are modelled by dividing a single day into multiple time intervals (multi-period problem), and network consumption is reduced by putting to sleep idle line cards and chassis. To preserve network resiliency we consider two different protection schemes, i.e. dedicated and shared protection, according to which a backup path is assigned to each demand and a certain amount of spare capacity has to be available on each link. Robustness to traffic variations is provided by means of a specific modelling framework that allows to tune the conservatism degree of the solutions and to take into account load variations of different magnitude. Furthermore, we impose some inter-period constraints necessary to guarantee network stability and preserve the device lifetime. Both exact and heuristic methods are proposed. Experimentations carried out with realistic networks operated with flow-based routing protocols (i.e. MPLS) show that significant savings, up to 30%, can be achieved also when both survivability and robustness are fully guaranteed

Ant Colony Optimization For Survivable Virtual Topology Mapping In Optical Wdm Networks

Tez (Yüksek Lisans) -- İstanbul Teknik Üniversitesi, Fen Bilimleri Enstitüsü, 2009Thesis (M.Sc.) -- İstanbul Technical University, Institute of Science and Technology, 2009İnternet kullanımının her geçen gün biraz daha yaygınlaşması, bant genişliği problemini de beraberinde getirmiştir. Bu ihtiyacı karşılamak amacıyla, optik ağlarda WDM (dalga boyu bölmeli çoğullama – wavelength division multiplexing) teknolojisi kullanılarak fiber kabloların kapasitesi, her biri farklı dalga boyunda çalışan yüzlerce farklı iletim kanalına bölünmüştür. Paket iletimi yapan üst katmanların kullanacağı uçtan uca kurulan optik bağlantılara ışıkyolu denir. Ağda kurulan tüm ışıkyolları ağın sanal topolojisini oluşturur. Bir fiber üzerinde farklı dalga boylarında olmak koşuluyla birden fazla ışıkyolu yönlendirilebilir. Fakat bir fiberin herhangi bir şekilde hasara uğraması, üzerinden geçen bütün ışıkyollarının kopması sonucu ciddi boyutlarda veri kaybına neden olur. Bu durumdan korunma yöntemlerinden biri ışıkyollarının fiberler üzerinde hataya bağışık şekilde yönlendirilmesidir öyle ki fiziksel katmanda bir ya da daha fazla bağlantı koptuğunda sanal topoloji hala bağlı kalmalıdır. Bu çalışmanın amacı altı farklı karınca koloni algoritması kullanılarak fiberlerin kapasite kısıtlarını aşmadan ve ağ kaynaklarının kullanımını minimize edecek şekilde ışıkyollarını hataya bağışık olarak fiziksel topoloji üzerinde yönlendirmek ve algoritmaları başarım, hız ve ağ kaynaklarının etkin kullanımı açısından karşılaştırmaktır.As the internet use increases significantly in everyday life, the need for bandwidth increases accordingly. To meet this need, high capacity of fibers used in optical networks, can be divided into many channels, using the WDM technology. End-to-end optical connections that the packet layer (IP, Ethernet, etc.) uses are called lightpaths. All the lightpaths set up on the network form the virtual topology. A fiber is able to route more than one ligthpaths with different wavelengths. Any damage to a fiber causes all the channels routed through this link to be broken, which may result in a serious amount of data loss. As a solution to this problem, the virtual layer can be mapped onto the physical topology, such that, a failure on any physical link does not disconnect the virtual topology. This is known as the survivable virtual topology mapping problem. In this study, our aim is to compare the performance of six different ant colony algorithms in finding a survivable mapping of a given virtual topology while minimizing the used wavelength links and without violating the wavelength capacity of fibers in terms of success rates, speed and resource usage.Yüksek LisansM.Sc

Operating mesh-survivable WDM transport networks

All-optical networks with wavelength-division multiplexing (WDM) are considered to be a promising technology for next generation transport networks, as they can satisfy the growing bandwidth demand caused primarily due to an explosive growth of web-related services over the Internet. As the traffic demand increases, survivability becomes an indispensable requirement in WDM transport networks. This motivates the need for addressing failure restoration as an integral part of optical network design and operation. To date, the design problems have considered a static traffic demand aimed at optimizing the network capacity and cost, assuming various cost and survivability models. In this paper, we formulate three operational phases viz., initial call setup, medium-term reconfiguration when connections are blocked, and long-term reconfiguration to optimize resource utilization for the existing traffic, as a single Integer Linear Programming (ILP) optimization problem. This integrated framework is an attractive formulation that captures both capacity optimization and service disruption aspect in the problem formulation