The Internet has led to the creation of a digital society, where (almost) everything is connected and is accessible from anywhere. However, despite their widespread adoption, traditional IP networks are complex and very hard to manage. It is both difficult to configure the network according to predefined policies, and to reconfigure it to respond to faults, load, and changes. To make matters even more difficult, current networks are also vertically integrated: the control and data planes are bundled together. Software-defined networking (SDN) is an emerging paradigm that promises to change this state of affairs, by breaking vertical integration, separating the network's control logic from the underlying routers and switches, promoting (logical) centralization of network control, and introducing the ability to program the network. The separation of concerns, introduced between the definition of network policies, their implementation in switching hardware, and the forwarding of traffic, is key to the desired flexibility: by breaking the network control problem into tractable pieces, SDN makes it easier to create and introduce new abstractions in networking, simplifying network management and facilitating network evolution. In this paper, we present a comprehensive survey on SDN. We start by introducing the motivation for SDN, explain its main concepts and how it differs from traditional networking, its roots, and the standardization activities regarding this novel paradigm. Next, we present the key building blocks of an SDN infrastructure using a bottom-up, layered approach. We provide an in-depth analysis of the hardware infrastructure, southbound and northbound application programming interfaces (APIs), network virtualization layers, network operating systems (SDN controllers), network programming languages, and network applications. We also look at cross-layer problems such as debugging and troubleshooting. In an effort to anticipate the future evolution of this new paradigm, we discuss the main ongoing research efforts and challenges of SDN. In particular, we address the design of switches and control platforms—with a focus on aspects such as resiliency, scalability, performance, security, and dependability—as well as new opportunities for carrier transport networks and cloud providers. Last but not least, we analyze the position of SDN as a key enabler of a software-defined environment.

https://publications.uni.lu/bitstream/10993/20596/1/survey_on_SDN.pdf

Software-Defined Networking: A Comprehensive Survey

Software-Defined Networking (SDN) is an emerging paradigm that promises to change this state of affairs, by breaking vertical integration, separating the network's control logic from the underlying routers and switches, promoting (logical) centralization of network control, and introducing the ability to program the network. The separation of concerns introduced between the definition of network policies, their implementation in switching hardware, and the forwarding of traffic, is key to the desired flexibility: by breaking the network control problem into tractable pieces, SDN makes it easier to create and introduce new abstractions in networking, simplifying network management and facilitating network evolution. In this paper we present a comprehensive survey on SDN. We start by introducing the motivation for SDN, explain its main concepts and how it differs from traditional networking, its roots, and the standardization activities regarding this novel paradigm. Next, we present the key building blocks of an SDN infrastructure using a bottom-up, layered approach. We provide an in-depth analysis of the hardware infrastructure, southbound and northbound APIs, network virtualization layers, network operating systems (SDN controllers), network programming languages, and network applications. We also look at cross-layer problems such as debugging and troubleshooting. In an effort to anticipate the future evolution of this new paradigm, we discuss the main ongoing research efforts and challenges of SDN. In particular, we address the design of switches and control platforms -- with a focus on aspects such as resiliency, scalability, performance, security and dependability -- as well as new opportunities for carrier transport networks and cloud providers. Last but not least, we analyze the position of SDN as a key enabler of a software-defined environment.

Certain data-communication protocols hog the spotlight, but all of them have a lot in common. Computer Networking: A Top-Down Approach Featuring the Internet explains the engineering problems that are inherent in communicating digital information from point to point. The top-down approach mentioned in the subtitle means that the book starts at the top of the protocol stack--at the application layer--and works its way down through the other layers, until it reaches bare wire. The authors, for the most part, shun the well-known seven-layer Open Systems Interconnection (OSI) protocol stack in favor of their own five-layer (application, transport, network, link, and physical) model. It's an effective approach that helps clear away some of the hand waving traditionally associated with the more obtuse layers in the OSI model. The approach is definitely theoretical--don't look here for instructions on configuring Windows 2000 or a Cisco router--but it's relevant to reality, and should help anyone who needs to understand networking as a programmer, system architect, or even administration guru.The treatment of the network layer, at which routing takes place, is typical of the overall style. In discussing routing, authors James Kurose and Keith Ross explain (by way of lots of clear, definition-packed text) what routing protocols need to do: find the best route to a destination. Then they present the mathematics that determine the best path, show some code that implements those algorithms, and illustrate the logic by using excellent conceptual diagrams. Real-life implementations of the algorithms--including Internet Protocol (both IPv4 and IPv6) and several popular IP routing protocols--help you to make the transition from pure theory to networking technologies. --David WallTopics covered: The theory behind data networks, with thorough discussion of the problems that are posed at each level (the application layer gets plenty of attention). For each layer, there's academic coverage of networking problems and solutions, followed by discussion of real technologies. Special sections deal with network security and transmission of digital multimedia.

Computer Networking: A Top-Down Approach

Emerging mega-trends (e.g., mobile, social, cloud, and big data) in information and communication technologies (ICT) are commanding new challenges to future Internet, for which ubiquitous accessibility, high bandwidth, and dynamic management are crucial. However, traditional approaches based on manual configuration of proprietary devices are cumbersome and error-prone, and they cannot fully utilize the capability of physical network infrastructure. Recently, software-defined networking (SDN) has been touted as one of the most promising solutions for future Internet. SDN is characterized by its two distinguished features, including decoupling the control plane from the data plane and providing programmability for network application development. As a result, SDN is positioned to provide more efficient configuration, better performance, and higher flexibility to accommodate innovative network designs. This paper surveys latest developments in this active research area of SDN. We first present a generally accepted definition for SDN with the aforementioned two characteristic features and potential benefits of SDN. We then dwell on its three-layer architecture, including an infrastructure layer, a control layer, and an application layer, and substantiate each layer with existing research efforts and its related research areas. We follow that with an overview of the de facto SDN implementation (i.e., OpenFlow). Finally, we conclude this survey paper with some suggested open research challenges.

A Survey on Software-Defined Networking

We describe the design and implementation of Open vSwitch, a multi-layer, open source virtual switch for all major hypervisor platforms. Open vSwitch was designed de novo for networking in virtual environments, resulting in major design departures from traditional software switching architectures. We detail the advanced flow classification and caching techniques that Open vSwitch uses to optimize its operations and conserve hypervisor resources. We evaluate Open vSwitch performance, drawing from our deployment experiences over the past seven years of using and improving Open vSwitch.

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The design and implementation of open vSwitch

Recent efforts in software-defined networks, such as OpenFlow, give unprecedented access into the forwarding plane of networking equipment. When building a network based on OpenFlow however, one must take into account the performance characteristics of particular OpenFlow switch implementations. In this paper, we present OFLOPS, an open and generic software framework that permits the development of tests for OpenFlow-enabled switches, that measure the capabilities and bottlenecks between the forwarding engine of the switch and the remote control application. OFLOPS combines hardware instrumentation with an extensible software framework.

We use OFLOPS to evaluate current OpenFlow switch implementations and make the following observations: (i) The switching performance of flows depends on applied actions and firmware. (ii) Current OpenFlow implementations differ substantially in flow updating rates as well as traffic monitoring capabilities. (iii) Accurate OpenFlow command completion can be observed only through the data plane. These observations are crucial for understanding the applicability of Open- Flow in the context of specific use-cases, which have requirements in terms of forwarding table consistency, flow setup latency, flow space granularity, packet modification types, and/or traffic monitoring abilities.

/pdf/oflops-an-open-framework-for-openflow-switch-evaluation-1myplkmdhs.pdf

OFLOPS: an open framework for openflow switch evaluation

The largest IXPs carry on a daily basis traffic volumes in the petabyte range, similar to what some of the largest global ISPs reportedly handle. This little-known fact is due to a few hundreds of member ASes exchanging traffic with one another over the IXP's infrastructure. This paper reports on a first-of-its-kind and in-depth analysis of one of the largest IXPs worldwide based on nine months' worth of sFlow records collected at that IXP in 2011.A main finding of our study is that the number of actual peering links at this single IXP exceeds the number of total AS links of the peer-peer type in the entire Internet known as of 2010! To explain such a surprisingly rich peering fabric, we examine in detail this IXP's ecosystem and highlight the diversity of networks that are members at this IXP and connect there with other member ASes for reasons that are similarly diverse, but can be partially inferred from their business types and observed traffic patterns. In the process, we investigate this IXP's traffic matrix and illustrate what its temporal and structural properties can tell us about the member ASes that generated the traffic in the first place. While our results suggest that these large IXPs can be viewed as a microcosm of the Internet ecosystem itself, they also argue for a re-assessment of the mental picture that our community has about this ecosystem.

http://conferences.sigcomm.org/sigcomm/2012/paper/sigcomm/p163.pdf

Anatomy of a large european IXP

Internet traffic has Zipf-like properties at multiple aggregation levels. These properties suggest the possibility of offloading most of the traffic from a complex controller (e.g., a software router) to a simple forwarder (e.g., a commodity switch), by letting the forwarder handle a very limited set of flows; the heavy hitters. As the volume of traffic from a set of flows is highly dynamic, maintaining a reliable set of heavy hitters over time is challenging. This is especially true when we face a volume limit in the non-offloaded traffic in combination with a constraint in the size of the heavy hitter set or its rate of change. We propose a set selection strategy that takes advantage of the properties of heavy hitters at different time scales. Based on real Internet traffic traces, we show that our strategy is able to offload most of the traffic while limiting the rate of change of the heavy hitter set, suggesting the feasibility of alternative router designs.

/pdf/leveraging-zipf-s-law-for-traffic-offloading-2722cgs41k.pdf

Leveraging Zipf's law for traffic offloading

With wireless technologies becoming prevalent at the last hop, today's network operators need to manage WiFi access networks in unison with their wired counterparts. However, the non-uniformity of feature sets in existing solutions and the lack of programmability makes this a challenging task. This paper proposes Odin, an SDN-based solution to bridge this gap. With Odin, we make the following contributions: (i) Light Virtual Access Points (LVAPs), a novel programming abstraction for addressing the IEEE 802.11 protocol stack complexity, (ii) a design and implementation for a software-defined WiFi network architecture based on LVAPs, and (iii) a prototype implementation on top of commodity access point hardware without modifications to the IEEE 802.11 client, making it practical for today's deployments. To highlight the effectiveness of the approach we demonstrate six WiFi network services on top of Odin including load-balancing, mobility management, jammer detection, automatic channel-selection, energy management, and guest policy enforcement. To further foster the development of our framework, the Odin prototype is made publicly available.

/pdf/programmatic-orchestration-of-wifi-networks-59zyb8f275.pdf

Programmatic orchestration of WiFi networks

Applying the concept of SDN to WiFi networks is challenging, since wireless networks feature many peculiarities and knobs that often do not exist in wired networks: obviously, WiFi communicates over a shared medium, with all its implications, e.g., higher packet loss and hidden or exposed terminals. Moreover, wireless links can be operated in a number of different regimes, e.g., transmission rate and power settings can be adjusted, RTS/CTS mechanisms can be used. Indeed, due to the non-stationary characteristic of the wireless channel, permanently adjusting settings such as transmission rate and power is crucial for the performance of WiFi networks and brings significant benefits in the service quality, e.g., through reducing the packet loss probability. Today’s rate and power control is mainly done on the WiFi device itself. But it is rarely optimized to the application-layer demands and their diverse traffic requirements, e.g., their individual sensitivity to packet loss or jitter. Therefore, if SDN for wireless can provide mechanisms to control the WiFi-specific transmission settings on a per-slice, per-client, and per-flow level, traffic and application-aware optimizations are feasible. This however requires that controllers frequently collect link characteristics and, accordingly, adjust transmission settings in a timely manner. As a reference, the standard rate control mechanism in the Linux kernel adjusts the transmission rate on a wireless link based on transmission success probability statistics every 100 ms. Leaving rate control (and power control accordingly) to a centralized controller comes with a risk of overloading the control plane, or of adding too much latency, while there is limited benefit in maintaining these statistics globally. For instance, the coherence time (also a function of the client mobility) can easily exceed the expected time of the successful transmission of multiple data frames [2], rendering optimized control difficult. In this paper, we suggest a 2-tiered approach for the design of a wireless SDN control plane. Our design, called AeroFlux, handles frequent, localized events close to where they originate, i.e., close to the data plane, by relying on NearSighted Controllers (NSC) [3, 4, 7]. Global events, which require a broader picture of the network’s state, are handled by the Global Controller (GC). More specifically, GC takes care of network functions that require global visibility, such as mobility management and load balancing, whereas NSCs control per-client or per-flow transmission settings such as rate and power based on transmission status feedback information exported by the Access Points (AP), which include the rates for best throughput and best transmission probability. Put differently, we enable the global controller to offload latency-critical or high-load tasks from the tier-1 control plane to the NSCs. This reduces the load on the GC and lowers the latency of critical control plane operations. As a result, with AeroFlux, we realize a scalable wireless SDN architecture which can support large enterprise and carrier WiFi deployments with low-latency programmatic control of fine-grained WiFi-specific transmission settings. The AeroFlux design introduces a set of new trade-offs and optimization opportunities which allow for advancements in the use of the shared wireless medium, and, as a result, in the user’s quality of experience. For instance, our prototype’s perflow control allows application-aware service differentiation by prioritizing multimedia streams (§2). Another key feature of AeroFlux is that it does not require modifications to today’s hardware and works on top of commodity WiFi equipment. 1 The AeroFlux Architecture AeroFlux uses a 2-tiered control plane: the Global Control plane GC and the Near-Sighted Control plane NSC. Figure 1 depicts the high level interactions of the architecture’s building blocks. The GC is logically centralized, e.g., a set of redundant controllers deployed in data centers, whereas the NSCs are located closer to where they are needed, e.g., close to the wireless APs. On the APs runs a Radio Agent (RA), which hosts the Light Virtual Access Points (LVAPs) [6] that abstract the specifics of the 802.11 protocol, such as association and authentication state. Furthermore, LVAPs store per-client OpenFlow and WiFi Datapath Transmission (WDTX) rules. In the following, we describe the different elements in more detail. Global Controller (GC): The global controller handles events which are not time-critical [7] or events belonging to inherently global tasks [4]. Examples include: authentication, wide-area mobility management, global policy verification (including loop-free forwarding sets), client load balancing, and applications for intrusion detection or network monitoring. In addition, the global controller is best suited to man-

/pdf/aeroflux-a-near-sighted-controller-architecture-for-software-2pjhenbvlv.pdf

Nadi Sarrar

Papers

OFLOPS: an open framework for openflow switch evaluation

Anatomy of a large european IXP

Leveraging Zipf's law for traffic offloading

Programmatic orchestration of WiFi networks

AeroFlux: A Near-Sighted Controller Architecture for Software-Defined Wireless Networks