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

P4 is a high-level language for programming protocol-independent packet processors. P4 works in conjunction with SDN control protocols like OpenFlow. In its current form, OpenFlow explicitly specifies protocol headers on which it operates. This set has grown from 12 to 41 fields in a few years, increasing the complexity of the specification while still not providing the flexibility to add new headers. In this paper we propose P4 as a strawman proposal for how OpenFlow should evolve in the future. We have three goals: (1) Reconfigurability in the field: Programmers should be able to change the way switches process packets once they are deployed. (2) Protocol independence: Switches should not be tied to any specific network protocols. (3) Target independence: Programmers should be able to describe packet-processing functionality independently of the specifics of the underlying hardware. As an example, we describe how to use P4 to configure a switch to add a new hierarchical label.

/pdf/p4-programming-protocol-independent-packet-processors-jlla1kwsyr.pdf

P4: programming protocol-independent packet processors

The idea of programmable networks has recently re-gained considerable momentum due to the emergence of the Software-Defined Networking (SDN) paradigm. SDN, often referred to as a ''radical new idea in networking'', promises to dramatically simplify network management and enable innovation through network programmability. This paper surveys the state-of-the-art in programmable networks with an emphasis on SDN. We provide a historic perspective of programmable networks from early ideas to recent developments. Then we present the SDN architecture and the OpenFlow standard in particular, discuss current alternatives for implementation and testing of SDN-based protocols and services, examine current and future SDN applications, and explore promising research directions based on the SDN paradigm.

/pdf/a-survey-of-software-defined-networking-past-present-and-6tt309ed7r.pdf

A Survey of Software-Defined Networking: Past, Present, and Future of Programmable Networks

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.

Network virtualization is recognized as an enabling technology for the future Internet. It aims to overcome the resistance of the current Internet to architectural change. Application of this technology relies on algorithms that can instantiate virtualized networks on a substrate infrastructure, optimizing the layout for service-relevant metrics. This class of algorithms is commonly known as "Virtual Network Embedding (VNE)" algorithms. This paper presents a survey of current research in the VNE area. Based upon a novel classification scheme for VNE algorithms a taxonomy of current approaches to the VNE problem is provided and opportunities for further research are discussed.

Virtual Network Embedding: A Survey

A controller for a software defined network may include a switch modeling interface that maintains switch models of switches in a network. The switch modeling interface may receive a desired network configuration from application modules that respond to network events. The switch modeling interface may compare the desired network configuration with the current network configuration represented by the switch models. The switch modeling interface may generate control messages to the switches for only identified differences between the desired network configuration and the current network configuration as identified by the switch models. The differences may be identified based on digest values retrieved from the switches. The switch modeling interface may determine whether the control messages were successfully received and processed by a switch and may indicate success or failure to the application module that provided the desired network configuration.

Systems and methods for controlling network switches using a switch modeling interface at a controller

In spite of the standardization of the OpenFlow API, it is very difficult to write an SDN controller application that is portable (i.e., guarantees correct packet processing over a wide range of switches) and achieves good performance (i.e., fully leverages switch capabilities). This is because the switch landscape is fundamentally diverse in performance, feature set and supported APIs. We propose to address this challenge via a lightweight portability layer that acts as a rendezvous point between the requirements of controller application and the vendor knowledge of switch implementations. Above, applications specify rules in virtual flow tables annotated with semantic intents and expectations. Below, vendor specific drivers map them to optimized switch-specific rule sets. NOSIX represents a first step towards achieving both portability and good performance across a diverse set of switches.

/pdf/nosix-a-lightweight-portability-layer-for-the-sdn-os-4owa8buvxc.pdf

NOSIX: a lightweight portability layer for the SDN OS

In this paper we leverage the structure of the SDN software stack to automate the process of troubleshooting networks. We present two techniques for programmatically localizing the root cause of network problems: crosslayer correspondence checking infers what problems exist in the network, and where in the control software the problem first developed; and simulation-based causal inference infers when the triggering event(s) occurred. We evaluated our tools on three popular SDN platforms— Frenetic, Floodlight and POX—and found or reproduced three bugs: isolation breaches and faulty failover logic between replicated controllers.

/pdf/what-where-and-when-software-fault-localization-for-sdn-3odb2w7728.pdf

What, Where, and When: Software Fault Localization for SDN

A method and system of analyzing a network to identify a network defect allows user selection of traffic subset to be recorded. After recording the selected traffic subset of the network traffic during network operation, the recorded traffic is then replayed at least in part to the network to replicate, and thus assist in identifying, the network defect.

Virtualization and replay-based system for network debugging

Software bugs are inevitable in software-defined networking (SDN) control planes, and troubleshooting is a tedious, time-consuming task. In this paper we discuss how one might improve SDN network troubleshooting by presenting a technique, retrospective causal inference, for automatically identifying a minimal sequence of inputs responsible for triggering a given bug in the control software. Retrospective causal inference works by iteratively pruning inputs from the history of the execution, and coping with divergent histories by reasoning about the functional equivalence of events. We apply retrospective causal inference to three open source SDN control platforms—Floodlight, POX, and NOX—and illustrate how our technique found minimal causal sequences for the bugs we encountered.

/pdf/how-did-we-get-into-this-mess-isolating-fault-inducing-2fovb8ac8y.pdf

Andreas Wundsam

Papers

Systems and methods for controlling network switches using a switch modeling interface at a controller

NOSIX: a lightweight portability layer for the SDN OS

What, Where, and When: Software Fault Localization for SDN

Virtualization and replay-based system for network debugging

How Did We Get Into This Mess? Isolating Fault- Inducing Inputs to SDN Control Software