Communications of the ACM (CACM for short, not the best sounding acronym around) is the ACM’s flagship magazine. Started in 1957, CACM is handy for keeping up to date on current research being carried out across all topics of computer science and realworld applications. CACM has had an illustrious past with many influential pieces of work and debates started within its pages. These include Hoare’s presentation of the Quicksort algorithm; Rivest, Shamir and Adleman’s description of the first publickey cryptosystem RSA; and Dijkstra’s famous letter against the use of GOTO. In addition to the print edition, which is released monthly, there is a fantastic website (http://cacm.acm. org/) that showcases not only the most recent edition but all previous CACM articles as well, readable online as well as downloadable as a PDF. In addition, the website lets you browse for articles by subject, a handy feature if you want to focus on a particular topic. CACM is really essential reading. Pretty much guaranteed to contain content that is interesting to anyone, it keeps tabs on the latest in computer science. It is a valuable asset for us students, who tend to delve deep into a particular area of CS and forget everything that is happening around us. — Daniel Gooch U ndergraduate research is like a box of chocolates: You never know what kind of project you will get. That being said, there are still a few things you should know to get the most out of the experience.

Communications of the ACM

A survey

As opposed to the decentralized control logic underpinning the devising of the Internet as a complex bundle of box-centric protocols and vertically integrated solutions, the software-defined networking (SDN) paradigm advocates the separation of the control logic from hardware and its centralization in software-based controllers. These key tenets offer new opportunities to introduce innovative applications and incorporate automatic and adaptive control aspects, thereby, easing network management and guaranteeing the user’s quality of experience. Despite the excitement, SDN adoption raises many challenges including the scalability and reliability issues of centralized designs that can be addressed with the physical decentralization of the control plane. However, such physically distributed, but logically centralized systems bring an additional set of challenges. This paper presents a survey on SDN with a special focus on the distributed SDN control. Besides reviewing the SDN concept and studying the SDN architecture as compared to the classical one, the main contribution of this survey is a detailed analysis of state-of-the-art distributed SDN controller platforms which assesses their advantages and drawbacks and classifies them in novel ways (physical and logical classifications) in order to provide useful guidelines for SDN research and deployment initiatives. A thorough discussion on the major challenges of distributed SDN control is also provided along with some insights into emerging and future trends in that area.

Distributed SDN Control: Survey, Taxonomy, and Challenges

Software defined networking (SDN) has emerged as a promising paradigm for making the control of communication networks flexible. SDN separates the data packet forwarding plane, i.e., the data plane, from the control plane and employs a central controller. Network virtualization allows the flexible sharing of physical networking resources by multiple users (tenants). Each tenant runs its own applications over its virtual network, i.e., its slice of the actual physical network. The virtualization of SDN networks promises to allow networks to leverage the combined benefits of SDN networking and network virtualization and has therefore attracted significant research attention in recent years. A critical component for virtualizing SDN networks is an SDN hypervisor that abstracts the underlying physical SDN network into multiple logically isolated virtual SDN networks (vSDNs), each with its own controller. We comprehensively survey hypervisors for SDN networks in this paper. We categorize the SDN hypervisors according to their architecture into centralized and distributed hypervisors. We furthermore sub-classify the hypervisors according to their execution platform into hypervisors running exclusively on general-purpose compute platforms, or on a combination of general-purpose compute platforms with general- or special-purpose network elements. We exhaustively compare the network attribute abstraction and isolation features of the existing SDN hypervisors. As part of the future research agenda, we outline the development of a performance evaluation framework for SDN hypervisors.

Survey on Network Virtualization Hypervisors for Software Defined Networking

Distributed denial-of-service (DDoS) attacks have become a weapon of choice for hackers, cyber extortionists, and cyber terrorists. These attacks can swiftly incapacitate a victim, causing huge revenue losses. Despite the large number of traditional mitigation solutions that exists today, DDoS attacks continue to grow in frequency, volume, and severity. This calls for a new network paradigm to address the requirements of today’s challenging security threats. Software-defined networking (SDN) is an emerging network paradigm which has gained significant traction by many researchers to address the requirement of today’s data centers. Inspired by the capabilities of SDN, we present a comprehensive survey of existing SDN-based DDoS attack detection and mitigation solutions. We classify solutions based on DDoS attack detection techniques and identify requirements of an effective solution. Based on our findings, we propose a novel framework for detection and mitigation of DDoS attacks in a large-scale network which comprises a smart city built on SDN infrastructure. Our proposed framework is capable of meeting application-specific DDoS attack detection and mitigation requirements. The primary contribution of this paper is twofold. First, we provide an in-depth survey and discussion of SDN-based DDoS attack detection and mitigation mechanisms, and we classify them with respect to the detection techniques. Second, leveraging the characteristics of SDN for network security, we propose and present an SDN-based proactive DDoS Defense Framework (ProDefense). We show how this framework can be utilized to secure applications built for smart cities. Moreover, the paper highlights open research challenges, future research directions, and recommendations related to SDN-based DDoS detection and mitigation.

DDoS Attack Detection and Mitigation Using SDN: Methods, Practices, and Solutions

This paper presents an independent comprehensive analysis of the efficiency indexes of popular open source SDN/OpenFlow controllers (NOX, POX, Beacon, Floodlight, MuL, Maestro, Ryu). The analysed indexes include performance, scalability, reliability, and security. For testing purposes we developed the new framework called hcprobe. The test bed and the methodology we used are discussed in detail so that everyone could reproduce our experiments. The result of the evaluation show that modern SDN/OpenFlow controllers are not ready to be used in production and have to be improved in order to increase all above mentioned characteristics.

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Advanced study of SDN/OpenFlow controllers

In SDN network based on OpenFlow a controller performs logically centralized control of enterprise network infrastructure, network policies, and data flows. At the same time the controller is a single point of failure which can cause a very serious problem (e.g. network outage) for network reliability and production use cases. To address this problem, we consider different active/standby strategies to provide a controller failover in case of controller failure. We propose a high-available controller (HAC) architecture, which allows to deploy a high-availability control plane for enterprise networks. We develop a HAC prototype to demonstrate the efficiency of our solution and also describe initial experimental results.

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Controller failover for SDN enterprise networks

The Internet routing ecosystem is facing substantial scalability challenges due to continuous, significant growth of the state represented in the data plane. Distributed switch architectures introduce additional constraints on efficient implementations from both lookup time and memory footprint perspectives. In this work we explore efficient FIB representations in common distributed switch architectures. Our approach introduces substantial savings in memory footprint transparently for existing hardware. Our results are supported by an extensive simulation study on real IPv4 and IPv6 FIBs.

FIB efficiency in distributed platforms

The Runos is a C++ OpenFlow controller that has been developing since 2014 in order to answer on the well-known question "Could an OpenFlow controller be both easy to develop applications for and also high performance?" [1]. The controller includes the most fruitful techniques from the latest research on simplifying SDN programming such as Pyretic and Maple and combines them in right way to achieve high performance and production quality, programmability, usability. Runos is widely used in different POCs showing interests for third-party developers. The project is in http://arccn.github.io/runos/.

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The Runos OpenFlow Controller

The Internet routing ecosystem is facing substantial scalability challenges on the data plane. Various “clean slate” architectures for representing forwarding tables (FIBs), such as IPv6, introduce additional constraints on efficient implementations from both lookup time and memory footprint perspectives due to significant classification width. In this work, we propose an abstraction layer able to represent IPv6 FIBs on existing IP and even MPLS infrastructure. Feasibility of the proposed representations is confirmed by an extensive simulation study on real IPv6 forwarding tables, including low-level experimental performance evaluation.

Alexander Shalimov

Papers

Advanced study of SDN/OpenFlow controllers

Controller failover for SDN enterprise networks

FIB efficiency in distributed platforms

The Runos OpenFlow Controller

How to represent IPv6 forwarding tables on IPv4 or MPLS dataplanes