Lifetime-aware cloud data centers: models and performance evaluation

We present a model to evaluate the server lifetime in cloud data centers (DCs). In particular, when the server power level is decreased, the failure rate tends to be reduced as a consequence of the limited number of components powered on. However, the variation between the different power states triggers a failure rate increase. We therefore consider these two effects in a server lifetime model, subject to an energy-aware management policy. We then evaluate our model in a realistic case study. Our results show that the impact on the server lifetime is far from negligible. As a consequence, we argue that a lifetime-aware approach should be pursued to decide how and when to apply a power state change to a server

Effectiveness of segment routing technology in reducing the bandwidth and cloud resources provisioning times in network function virtualization architectures

Network Function Virtualization is a new technology allowing for a elastic cloud and bandwidth resource allocation. The technology requires an orchestrator whose role is the service and resource orchestration. It receives service requests, each one characterized by a Service Function Chain, which is a set of service functions to be executed according to a given order. It implements an algorithm for deciding where both to allocate the cloud and bandwidth resources and to route the SFCs. In a traditional orchestration algorithm, the orchestrator has a detailed knowledge of the cloud and network infrastructures and that can lead to high computational complexity of the SFC Routing and Cloud and Bandwidth resource Allocation (SRCBA) algorithm. In this paper, we propose and evaluate the effectiveness of a scalable orchestration architecture inherited by the one proposed within the European Telecommunications Standards Institute (ETSI) and based on the functional separation of an NFV orchestrator in Resource Orchestrator (RO) and Network Service Orchestrator (NSO). Each cloud domain is equipped with an RO whose task is to provide a simple and abstract representation of the cloud infrastructure. These representations are notified of the NSO that can apply a simplified and less complex SRCBA algorithm. In addition, we show how the segment routing technology can help to simplify the SFC routing by means of an effective addressing of the service functions. The scalable orchestration solution has been investigated and compared to the one of a traditional orchestrator in some network scenarios and varying the number of cloud domains. We have verified that the execution time of the SRCBA algorithm can be drastically reduced without degrading the performance in terms of cloud and bandwidth resource costs

Segment Routing: a Comprehensive Survey of Research Activities, Standardization Efforts and Implementation Results

Fixed and mobile telecom operators, enterprise network operators and cloud providers strive to face the challenging demands coming from the evolution of IP networks (e.g. huge bandwidth requirements, integration of billions of devices and millions of services in the cloud). Proposed in the early 2010s, Segment Routing (SR) architecture helps face these challenging demands, and it is currently being adopted and deployed. SR architecture is based on the concept of source routing and has interesting scalability properties, as it dramatically reduces the amount of state information to be configured in the core nodes to support complex services. SR architecture was first implemented with the MPLS dataplane and then, quite recently, with the IPv6 dataplane (SRv6). IPv6 SR architecture (SRv6) has been extended from the simple steering of packets across nodes to a general network programming approach, making it very suitable for use cases such as Service Function Chaining and Network Function Virtualization. In this paper we present a tutorial and a comprehensive survey on SR technology, analyzing standardization efforts, patents, research activities and implementation results. We start with an introduction on the motivations for Segment Routing and an overview of its evolution and standardization. Then, we provide a tutorial on Segment Routing technology, with a focus on the novel SRv6 solution. We discuss the standardization efforts and the patents providing details on the most important documents and mentioning other ongoing activities. We then thoroughly analyze research activities according to a taxonomy. We have identified 8 main categories during our analysis of the current state of play: Monitoring, Traffic Engineering, Failure Recovery, Centrally Controlled Architectures, Path Encoding, Network Programming, Performance Evaluation and Miscellaneous...Comment: SUBMITTED TO IEEE COMMUNICATIONS SURVEYS & TUTORIAL

Incremental deployment of segment routing into an ISP network: a traffic engineering perspective

Segment routing (SR) is a new routing paradigm to provide traffic engineering (TE) capabilities in an IP network. The main feature of SR is that no signaling protocols are needed, since extensions of the interior gateway protocol routing protocols are used. Despite the benefit that SR brings, introducing a new technology into an operational network presents many difficulties. In particular, the network operators consider both capital expenditure and performance degradation as drawbacks for the deployment of the new technology; for this reason, an incremental approach is preferred. In this paper, we face the challenge of managing the transition between a pure IP network to a full SR one while optimizing the network performances. We focus our attention on a network scenario where: 1) only a subset of nodes are SR-capable and 2) the TE objective is the minimization of the maximum link utilization. For such a scenario, we propose an architectural solution, named SR domain (SRD), to guarantee the proper interworking between the IP routers and the SR nodes. We propose a mixed integer linear programming formulation to solve the SRD design problem, consisting in identifying the subset of SR nodes; moreover, a strategy to manage the routing inside the SRD is defined. The performance evaluation shows that the hybrid IP/SR network based on SRD offers TE opportunities comparable to the one of a full SR network. Finally, a heuristic method to identify nodes to be inserted in the set of nodes composing the SRD is discussed

Translating Traffic Engineering outcome into Segment Routing paths: The Encoding problem

Traffic Engineering (TE) algorithms aims at determining the packet routing paths in order to satisfy specific QoS requirements. These paths are normally established through control procedures e.g., exchange of RSVP messages in MPLS networks or links weights modification in pure IP networks. An increase of control traffic or long convergence time intervals, respectively, are the drawbacks of these solutions. Segment Routing (SR) is a new network paradigm able to implement TE routing strategies over legacy IP/MPLS networks with no need of dedicated signaling procedures. This result is obtained by inserting in each packet header an ordered list of instructions, called Segments List, that indicates the path to be crossed. This paper provides the formulation of the Segment List Encoding problem i.e., the detection of the proper Segment Lists to obtain TE network paths minimizing the Segment Lists sizes. The SL encoding procedure is composed of two steps: i) the creation of an auxiliary graph representing the forwarding paths between the couple of source and destination nodes; ii) the solution of a Multi-commodity Flow (MCF) problem over the auxiliary graph. The performance evaluation shows that properly performing SL encoding allows to implement TE outcome with a reduced reconfiguration cost with respect to E2E tunneling and Hop-by-Hop solutions; moreover a significant advantage in terms of packets overhead is obtained

CApacity provisioning and PRIcing for cloud computing with energy capping

The past few years have been witnessing a surging demand for cloud computing services, resulting in a huge carbon footprint and making energy cost one of the top operational costs of data centers. Meanwhile, as sustainable computing has become increasingly important, data centers are constantly pressured to cap the long-term usage of their energy produced from carbon-intensive sources (a.k.a., 'brown' energy). In this paper, we study energy budgeting with dynamic pricing and propose a novel online algorithm, called CAPRI (CApacity provisioning and PRIcing), to maximize the profit of a data center while satisfying the energy capping constraint. We prove that CAPRI achieves a close-to-maximum profit compared to the optimal offline algorithm with future information, while bounding the potential violation of energy capping, in an almost arbitrarily random environment. We also perform a trace-based simulation study to complement the analysis and validate the effectiveness of CAPRI. © 2013 IEEE

Energy Saving Improvements in IP Networks Through Table Lookup Bypass in Router Line Cards

The present paper deals with the energy efficiency of an IP network and proposes a novel energy-aware strategy overcoming the simple switch-off of network elements. The proposed approach is called table lookup bypass (TLB) and consists in bypassing the table lookup operation performed by IP routers' line cards to forward packets. The basic idea is to freeze the forwarding engine of some line cards by forwarding incoming packets towards a single pre-determined outgoing interface. In this way a line card can be switched to a new state with a reduced energy consumption because its most power hungry functionality is disabled. The paper formalizes the energy consumption minimization problem when TLB capability is available in routers line cards in addition to the classical switch-off. Results demonstrate that the proposed strategy can significantly improve the network energy efficiency, especially when link switch-off is not possible or when the network is highly meshed, bringing additional saving up to 40% upon the classical link switch-off

Closing the gap among IP and per-flow green routing solutions. The tunneling approach

This paper proposes a novel energy-aware adaptive routing solution to face the energy consumption problem in IP networks, exploiting the IP over IP tunneling technique. The problem of minimizing the number of used links by configuring a set of tunnels, referred to as energy minimized tunneling (EMT), is modeled as an integer linear programming problem. The general EMT problem is then slightly modified by adding a set of constraints to make it more applicable to real networks scenario. With respect to previously proposed solutions, the EMT formulation exploits IP tunneling to change traffic routing assuring three main features: 1) no modifications to both data and control planes of current IP routers, so representing a feasible short-term solution for actual IP networks; 2) no need of IP routing protocols convergence to modify the routing paths, so avoiding routing instabilities; and 3) performance comparable with flow-based solutions requiring the deployment of a connection-oriented protocol. We propose a practical solution, called Virtual Interface oN Off (VINO), that exploits the tunnel aggregation mechanism in order to reduce EMT operational complexity. VINO works in two steps and it is based on the preconfiguration of a limited set of (virtual) tunnel interfaces along with a set of static routes on IP routers; thus, these virtual interfaces are dynamically activated and deactivated according to traffic variations. The performance analysis carried out demonstrates that VINO is able to outperform IP green routing solutions proposed in the literature, in terms of energy efficiency

Lifetime awareness in backbone networks with sleep modes

We investigate the problem of managing the lifetime of links in IP backbone networks exploiting a sleep mode (SM) state. In particular, the SM duration tends to increase the lifetime, while the frequency of power state transitions tends to decrease it. After optimally formulating the problem of limiting the impact on the link lifetime when SMs are applied, we propose an online heuristic, called AFA, to practically solve it. Our solution performs SMs decisions at each time slot, without requiring the knowledge of future traffic (which may be an unrealistic assumption). We test the performance of AFA on a realistic case study, by comparing it against two algorithms energy-aware. Results show that AFA outperforms the other algorithms in terms of lifetime performance, while allowing devices to be put in SMs

A heuristic approach to solve the Table Lookup Bypass problem

In this work we investigate a new solution dealing with the increase of IP networks energy efficiency. The starting point of this work is Table Lookup Bypass (TLB), a new mechanism to reduce the energy consumption of a linecard overcoming the simple switch-off of network elements: TLB consists in bypassing the lookup operation performed by a router linecard and forwarding the incoming packets on a fixed outgoing interface. The paper defines four different heuristics able to detect a set of TLB operations that can be performed maintaining QoS constraints. The performance evaluation realized on a real network scenario shows that TLB can really improve the energy efficiency of IP network, both during peak hours and off peak hours: in this last case up to 90% of linecards can pass in TLB state. © 2013 IEEE