The Transmission Control Protocol.

Network functions virtualization (NFV) is a new network architecture framework where network function that traditionally used dedicated hardware (middleboxes or network appliances) are now implemented in software that runs on top of general purpose hardware such as high volume server. NFV emerges as an initiative from the industry (network operators, carriers, and manufacturers) in order to increase the deployment flexibility and integration of new network services with increased agility within operator’s networks and to obtain significant reductions in operating expenditures and capital expenditures. NFV promotes virtualizing network functions such as transcoders, firewalls, and load balancers, among others, which were carried out by specialized hardware devices and migrating them to software-based appliances. One of the main challenges for the deployment of NFV is the resource allocation of demanded network services in NFV-based network infrastructures. This challenge has been called the NFV resource allocation (NFV-RA) problem. This paper presents a comprehensive state of the art of NFV-RA by introducing a novel classification of the main approaches that pose solutions to solve it. This paper also presents the research challenges that are still subject of future investigation in the NFV-RA realm.

Resource Allocation in NFV: A Comprehensive Survey

A Comprehensive Survey of Network Function Virtualization

This paper has the following ambitious goal: to convince the reader that content caching is an exciting research topic for the future communication systems and networks. Caching has been studied for more than 40 years, and has recently received increased attention from industry and academia. Novel caching techniques promise to push the network performance to unprecedented limits, but also pose significant technical challenges. This tutorial provides a brief overview of existing caching solutions, discusses seminal papers that open new directions in caching, and presents the contributions of this special issue. We analyze the challenges that caching needs to address today, also considering an industry perspective, and identify bottleneck issues that must be resolved to unleash the full potential of this promising technique.

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The Role of Caching in Future Communication Systems and Networks

To accelerate the implementation of network functions/middle boxes and reduce the deployment cost, recently, the concept of network function virtualization (NFV) has emerged and become a topic of much interest attracting the attention of researchers from both industry and academia. Unlike the traditional implementation of network functions, a software-oriented approach for virtual network functions (VNFs) creates more flexible and dynamic network services to meet a more diversified demand. Software-oriented network functions bring along a series of research challenges, such as VNF management and orchestration, service chaining, VNF scheduling for low latency and efficient virtual network resource allocation with NFV infrastructure, among others. In this paper, we study the VNF scheduling problem and the corresponding resource optimization solutions. Here, the VNF scheduling problem is defined as a series of scheduling decisions for network services on network functions and activating the various VNFs to process the arriving traffic. We consider VNF transmission and processing delays and formulate the joint problem of VNF scheduling and traffic steering as a mixed integer linear program. Our objective is to minimize the makespan/latency of the overall VNFs’ schedule. Reducing the scheduling latency enables cloud operators to service (and admit) more customers, and cater to services with stringent delay requirements, thereby increasing operators’ revenues. Owing to the complexity of the problem, we develop a genetic algorithm-based method for solving the problem efficiently. Finally, the effectiveness of our heuristic algorithm is verified through numerical evaluation. We show that dynamically adjusting the bandwidths on virtual links connecting virtual machines, hosting the network functions, reduces the schedule makespan by 15%–20% in the simulated scenarios.

Delay-Aware Scheduling and Resource Optimization With Network Function Virtualization

Network Functions Virtualization (NFV) is incrementally deployed by Internet Service Providers (ISPs) in their carrier networks, by means of Virtual Network Function (VNF) chains, to address customers' demands. The motivation is the increasing manageability, reliability and performance of NFV systems, the gains in energy and space granted by virtualization, at a cost that becomes competitive with respect to legacy physical network function nodes. From a network optimization perspective, the routing of VNF chains across a carrier network implies key novelties making the VNF chain routing problem unique with respect to the state of the art: the bitrate of each demand flow can change along a VNF chain, the VNF processing latency and computing load can be a function of the demands traffic, VNFs can be shared among demands, etc. In this paper, we provide an NFV network model suitable for ISP operations. We define the generic VNF chain routing optimization problem and devise a mixed integer linear programming formulation. By extensive simulation on realistic ISP topologies, we draw conclusions on the trade-offs achievable between legacy Traffic Engineering (TE) ISP goals and novel combined TE-NFV goals.

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Virtual network functions placement and routing optimization

The increasing adoption of server virtualization has recently favored three key technology advances in data-center networking: the emergence at the hypervisor software level of virtual bridging functions between virtual machines and the physical network; the possibility to dynamically migrate virtual machines across virtualization servers in the data-center network (DCN); a more efficient exploitation of the large path diversity by means of multipath forwarding protocols. In this paper, we investigate the impact of these novel features in DCN optimization by providing a comprehensive mathematical formulation and a repeated matching heuristic for its resolution. We show, in particular, how virtual bridging and multipath forwarding impact common DCN optimization goals, traffic engineering (TE) and energy efficiency (EE), and assess their utility in the various cases of four different DCN topologies. We show that virtual bridging brings a high performance gain when TE is the primary goal and should be deactivated when EE becomes important. Moreover, we show that multipath forwarding can bring relevant gains only when EE is the primary goal and virtual bridging is not enabled.

Striking a Balance Between Traffic Engineering and Energy Efficiency in Virtual Machine Placement

With the advent of network virtualization, data center networking is reaching a high level of management complexity. Indeed, interconnection networks in data center networks (DCN) are no longer just based on flat over-provisioned pipes, but are increasingly facing traffic engineering (TE) issues that commonly characterize long-haul provider networks. TE objectives, however, are opposite to energy efficiency (EE) objectives commonly chased by virtual machine (VM) consolidations. Moreover, the specific topologies of DCNs and the systematic use of multipath forwarding make the joint TE and VM consolidation optimization complex. The contribution of this paper is twofold. First, we propose a repeated matching heuristic for the DCN optimization problem with multipath capabilities, which also scales well for large topologies without discarding both TE and EE objectives. Second, we assess the impact of multipath forwarding on TE and EE goals. Extensive simulations show us that multipath forwarding is beneficial only when EE is not the primary goal in network-aware VM consolidations, and that it can be counterproductive when instead the EE is the primary goal of such optimizations.

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Impact of Ethernet Multipath Routing on Data Center Network Consolidations

Recently, two new distributed Link-flooding attacks with high destruction potential have been introduced named the Coremelt and the Crossfire attacks. Unlike the traditional DDoS attacks these two attacks isolate the victim from the rest of internet while the traffic is not sent to it. Moreover, these attacks are indistinguishable since the adversary keeps each per-flow rate, to flood the target network links, low for the Crossfire attack and only legitimate traffic is used for the Coremelt attack. The previous characteristics make these attacks undetectable by the current protection mechanisms in the routers or by intrusion detection systems (IDS). In this paper, we present a new mechanism that detects the sources used by the adversary to perform the attacks. Besides, we went one step further and we try to mitigate the attack even during the detection phase. This mechanism can be enabled by the softwarization mechanism as SDN. By extensive simulation on an ISP topology, and by comparing our work with previous solutions selected from the state of the art. Our results show that our heuristic is up to three times faster than the existing solutions and improve by ten the network stability. We believe that these results can help ISP enablers and designers to counter the link flooding attacks.

Centralized Defense Using Smart Routing Against Link-Flooding Attacks

The increasing adoption of virtualization techniques has recently favored the emergence of useful switching functions at the hypervisor level, commonly referred to as virtual bridging. In the context of data center network (DCN) consolidations, for VMs colocated in the same virtualization server, virtual bridging becomes very useful to offload inter-VM traffic from access and aggregation switches, at the expense of an additional computing load. DCN consolidations typically chase traffic engineering (TE) and energy efficiency (EE) objectives, and both should be affected by virtual bridging, but it is not intuitive to assert whether virtual bridging acts positively or negatively with respect to TE and EE that should also depend on the DCN topology and forwarding techniques. In this paper, we bring additional understanding about the impact of virtual bridging on DCN consolidations. First, we present a repeated matching heuristic for the generic multi-objective DCN optimization problem, with possible multipath and virtual bridging capabilities, accounting for both TE and EE objectives. Second, we assess the impact of virtual bridging on TE and EE in DeN consolidations. Extensive simulations show us that enabling virtual bridging has a negative impact when EE is the goal and multipath forwarding is adopted, while it leads to important gains, halving the maximum link utilization, when TE is the DeN consolidation goal.

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Dallal Belabed

Papers

Virtual network functions placement and routing optimization

Striking a Balance Between Traffic Engineering and Energy Efficiency in Virtual Machine Placement

Impact of Ethernet Multipath Routing on Data Center Network Consolidations

Centralized Defense Using Smart Routing Against Link-Flooding Attacks

Impact of virtual bridging on virtual machine placement in data center networking