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

A case for end system multicast

We present the design, implementation, and evaluation of B4, a private WAN connecting Google's data centers across the planet. B4 has a number of unique characteristics: i) massive bandwidth requirements deployed to a modest number of sites, ii) elastic traffic demand that seeks to maximize average bandwidth, and iii) full control over the edge servers and network, which enables rate limiting and demand measurement at the edge.These characteristics led to a Software Defined Networking architecture using OpenFlow to control relatively simple switches built from merchant silicon. B4's centralized traffic engineering service drives links to near 100% utilization, while splitting application flows among multiple paths to balance capacity against application priority/demands. We describe experience with three years of B4 production deployment, lessons learned, and areas for future work.

/pdf/b4-experience-with-a-globally-deployed-software-defined-wan-2ejcv4i1og.pdf

B4: experience with a globally-deployed software defined wan

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.

Today's data networks are surprisingly fragile and difficult to manage. We argue that the root of these problems lies in the complexity of the control and management planes--the software and protocols coordinating network elements--and particularly the way the decision logic and the distributed-systems issues are inexorably intertwined. We advocate a complete refactoring of the functionality and propose three key principles--network-level objectives, network-wide views, and direct control--that we believe should underlie a new architecture. Following these principles, we identify an extreme design point that we call "4D," after the architecture's four planes: decision, dissemination, discovery, and data. The 4D architecture completely separates an AS's decision logic from pro-tocols that govern the interaction among network elements. The AS-level objectives are specified in the decision plane, and en-forced through direct configuration of the state that drives how the data plane forwards packets. In the 4D architecture, the routers and switches simply forward packets at the behest of the decision plane, and collect measurement data to aid the decision plane in controlling the network. Although 4D would involve substantial changes to today's control and management planes, the format of data packets does not need to change; this eases the deployment path for the 4D architecture, while still enabling substantial innovation in network control and management. We hope that exploring an extreme design point will help focus the attention of the research and industrial communities on this crucially important and intellectually challenging area.

/pdf/a-clean-slate-4d-approach-to-network-control-and-management-2ks1hufhx0.pdf

A clean slate 4D approach to network control and management

The IP multicast delivery mechanism provides a popular basis for delivery of continuous media to many participants in a conferencing application. However, the best-effort nature of multicast delivery results in poor playback quality in the presence of network congestion and packet loss. Contrary to widespread belief that the real-time nature of continuous media applications precludes the possibility of recovery of lost packets using retransmissions, we have found that these applications offer an interesting tradeoff between the desired playback quality and the desired degree of interactivity. In particular, we propose a new model of multicast delivery called resilient multicast in which each receiver in a multicast group can decide its own tradeoff between reliability and real-time requirements. To be effective, error recovery mechanisms in such a model need to be both fast (due to the real-time constraint) and have a low overhead (due to high volume of continuous media data). We have designed a resilient multicast protocol called STORM (STructure-Oriented Resilient Multicast) in which senders and receivers collaborate to recover from lost packets using two key ideas. First, group participants self-organize themselves into a distribution structure and use the structure to recover lost packets from adjacent nodes. Second, the distribution structure is dynamic and a lightweight algorithm is used to adapt the structure to changing network traffic conditions and group membership. We have implemented STORM in both VAT and a packet level simulator. Experimental results using both the MBONE and a simulation model demonstrate the effectiveness of our approach.

/pdf/resilient-multicast-support-for-continuous-media-51dbp3coat.pdf

Resilient multicast support for continuous-media applications

As a growing number of Web sites introduce mirrors to increase throughput, the challenge for clients is determining which mirror will offer the best performance when a document is to be retrieved. We present findings from measuring 9 clients scattered throughout the United States retrieving over 490,000 documents from 47 production Web servers which mirror three different Web sites. We have several interesting findings that may aid in the design of protocols for choosing among mirror servers. Though server performance varies widely, we have observed that a server's performance relative to other servers is more stable and is independent of time scale. In addition, a change in an individual server's transfer time is not a strong indicator that its performance relative to other servers has changed. Finally, we have found that clients wishing to achieve near-optimal performance may only need to consider a small number of servers rather than all mirrors of a particular site.

/pdf/performance-characteristics-of-mirror-servers-on-the-osesa4jr2b.pdf

Performance characteristics of mirror servers on the Internet

We argue for the refactoring of the IP control plane to provide direct expressibility and support for network-wide goals relating to all fundamental functionality: reachability, performance, reliability and security. This refactoring is motivated by trends in operational practice and in networking technology. We put forward a design that decomposes functionality into information dissemination and decision planes. The decision plane is formed by lifting out of the routers all decision making logic currently found there and merging it with the current management plane where network-level objectives are specified. What is left on each router is a wafer-thin control plane focused on information dissemination and response to explicit instructions for configuring packet forwarding mechanisms. We discuss the consequences, advantages and challenges associated with this design.

/pdf/network-wide-decision-making-toward-a-wafer-thin-control-epuaxbi5yt.pdf

Network-Wide Decision Making: Toward A Wafer-Thin Control Plane

The current Web caching infrastructure, though it has a number of performance benefits for clients and network providers, does not meet publishers' requirements. We argue that to satisfy these requirements, caches should be enhanced in both the data and control planes. In the data plane, caches will dynamically generate content for clients by running code provided by publishers. In the control plane, caches will return logs of client accesses to publishers. In this paper, we introduce Gemini, a system which has both of these capabilities, and discuss two of its key components: security and incremental deployment. Since Gemini caches are deeply involved in content preparation and logging, ensuring that they perform correctly is vital. Traditional end-to-end security mechanisms are not sufficient to protect clients and publishers, so we introduce a new security model which consists of two pieces: an authorization mechanism and a verification mechanism. The former allows a publisher to authorize a set of caches to run its code and serve its content, while the latter allows clients and publishers to probabilistically verify that authorized caches are operating correctly. Because it is unrealistic to assume that Gemini caches will be deployed everywhere simultaneously, we have designed the system to be incrementally deployable and to coexist with legacy clients, caches, and servers. Finally, we describe our implementation of Gemini and present preliminary performance results.

/pdf/a-secure-publisher-centric-web-caching-infrastructure-1ofj3bfxnv.pdf

Andy Myers

Papers

A clean slate 4D approach to network control and management

Resilient multicast support for continuous-media applications

Performance characteristics of mirror servers on the Internet

Network-Wide Decision Making: Toward A Wafer-Thin Control Plane

A secure, publisher-centric Web caching infrastructure