Convergence of Probability Measures. By P. Billingsley. Chichester, Sussex, Wiley, 1968. xii, 253 p. 9 1/4“. 117s.

Convergence of Probability Measures

Social Network Analysis

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

Infectious Diseases Society of America.

The structure and dynamics of multilayer networks

The Internet realizes William Gibsons vision of Cyberspace: “A consensual hallucination experienced daily by billions of legitimate operators, in every nation As such it has changed the way that humans interact and provides the crucial foundation for a multitude of businesses. It has redefined expectations about how interactions between humans, computers and humans, and between computers function. Without question, almost all major industrial sectors take advantage of the Internet.

The Internet Architecture - Is a Redesign Needed?

Software-defined networks (SDNs) are built on the promise of consistency between control and data plane. Data plane consists of software or hardware and is subject to failures e.g., hardware or software bugs. Sometimes, these failures are outside the knowledge of the control plane consisting of network operating system or the SDN controller. The current state-of-the art tools either check the network statically from the control plane or use tagging or active probe generation to check the data plane behaviour. There is a spectrum of control plane mechanisms [1], [2], [3], [4] which check for some or all of the network-wide invariants like reachability, forwarding loops, waypoint enforcement and slice isolation. While most of the control plane mechanisms cannot model ECMP or NAT, all of them, however, are unaware of the actual behaviour on the data plane and thus, assume that control plane has a consistent view. There is a panoply of data plane mechanisms involving tagging [5], [6] or active probe generation [7], [8] which either check the path or the installed flow rules to monitor the data plane. Moreover, ping and traceroute continue to be the only tools available for network debugging to the network administrators in practice. Bugs in flow table match-action logic or switch hardware can manifest in various ways which are hard to detect and thus, to localize by any of the existing approaches. Moreover, tagging comes with its own limitations. There cannot be available and sufficient space for placing tags for a big scale scenario. Some of the existing mechanisms end up placing a lot of flow rules on the scarce TCAM to take action on tagged packets [5], [9]. The tagging mechanisms which end up tagging a packet on each switch may not detect faults where the output port is same but packet matched a different rule. Considering all of the above limitations, there is a need for a meticulous data plane monitoring tool. In software debugging, we design test cases which check the “code coverage” for finding possible faults, similarly, the monitoring tool should check all of the flow rules and links for possible faults and localize them.

Towards meticulous data plane monitoring

ICMP active probing is the center of many network measurements. Rate limiting to ICMP traffic, if undetected, could distort measurements and create false conclusions. To settle this concern, we look systematically for ICMP rate limiting in the Internet. We create FADER, a new algorithm that can identify rate limiting from user-side traces with minimal new measurement traffic. We validate the accuracy of FADER with many different network configurations in testbed experiments and show that it almost always detects rate limiting. With this confidence, we apply our algorithm to a random sample of the whole Internet, showing that rate limiting exists but that for slow probing rates, rate-limiting is very rare. For our random sample of 40,493 /24 blocks (about 2% of the responsive space), we confirm 6 blocks (0.02%!) see rate limiting at 0.39 packets/s per block. We look at higher rates in public datasets and suggest that fall-off in responses as rates approach 1 packet/s per /24 block is consistent with rate limiting. We also show that even very slow probing (0.0001 packet/s) can encounter rate limiting of NACKs that are concentrated at a single router near the prober.

/pdf/passive-and-active-measurement-1l3ott1zhh.pdf

Anja Feldmann

Papers

The Internet Architecture - Is a Redesign Needed?

Towards meticulous data plane monitoring

Passive and Active Measurement

Nanosensors in clinical development of CAR-T cell immunotherapy.

Development of Novel Anti-CD10 Target Modules for Redirection of Universal CAR T Cells Against CD10-Positive Malignancies