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

Inbound traffic engineering (ITE)---the process of announcing routes to, e.g., maximize revenue or minimize congestion---is an essential task for Autonomous Systems (ASes). AS Path Prepending (ASPP) is an easy to use and well-known ITE technique that routing manuals show as one of the first alternatives to influence other ASes' routing decisions. We observe that origin ASes currently prepend more than 25% of all IPv4 prefixes.ASPP consists of inflating the BGP AS path. Since the length of the AS path is the second tie-breaker in the BGP best path selection, ASPP can steer traffic to other routes. Despite being simple and easy to use, the appreciation of ASPP among operators and researchers is diverse. Some have questioned its need, effectiveness, and predictability, as well as voiced security concerns. Motivated by these mixed views, we revisit ASPP. Our longitudinal study shows that ASes widely deploy ASPP, and its utilization has slightly increased despite public statements against it. We surprisingly spot roughly 6k ASes originating at least one prefix with prepends that achieve no ITE goal. With active measurements, we show that ASPP effectiveness as an ITE tool depends on the AS location and the number of available upstreams; that ASPP security implications are practical; identify that more than 18% of the prepended prefixes contain unnecessary prepends that achieve no apparent goal other than amplifying existing routing security risks. We validate our findings in interviews with 20 network operators.

/pdf/as-path-prepending-there-is-no-rose-without-a-thorn-4pnl2k8bcr.pdf

AS-Path Prepending: there is no rose without a thorn

Due to the increasing significance of fast component technologies and the increasing complexity of printed circuit boards, electromagnetic phencmena, e.g. reflections and crosstalk, gain more and more importance and may even disturb the function of a printed circuit board. In the future, it will be indispensable to consider phenomena of electromagnclic compatibility (EMC) already during layout synthesis. In this paper robust methods are presented which, for the first time, make it possible to incorporate complex EMCconstraints and EMCcost criteria into printed circuit board routing. The results achieved so far are reported.

HERO: hierarchical EMC-constrained routing

Regulatory T cells (Tregs) are major players in immune homeostasis, and defects in their number and/or function are associated with a broad range of immunological disorders including autoimmunity, graft-versus-host disease (GvHD), transplant rejection, chronic infections or malignant diseases.1, 2 One way of how Tregs actively damp an immune response might be direct induction of apoptosis in activated antigen-presenting cells as well as in conventional effector T cells (Teffs) by secretion of lytic granzyme- and perforin-containing granula. Despite the substantial progress made in our understanding of Treg biology, the cytotoxic potential of Tregs is still under debate. As Tregs are under intense investigation as cellular therapeutics for treatment of GvHD and graft rejection, and might also interfere with novel antitumor strategies,3 this question is not a purely academic one but also implies major consequences for the prospective development of clinical treatment strategies involving Tregs. To shed some light on this controversial issue, we decided to analyze this question using peripheral human Tregs, as these cells are one major source for potential therapeutic applications.1, 2 As Tregs are a very rare population in human peripheral blood, it seems currently technically too challenging to isolate sufficient Treg numbers with defined antigen-specificity in a way as it can be done for—for example, virus- or tumor-specific Teffs. Therefore, in this study recombinant bispecific antibodies (bsAb) were applied for antigen-specific redirection of polyclonal human T cells as surrogate for T-cell receptor (TCR)-mediated stimulation. BsAb comprise binding sites for two different target antigens (for example, CD3 and a cell surface antigen) and can directly cross-link T cells and antigen-expressing cells. This results in a major histocompatibility complex (MHC)- and TCR-independent activation and triggering of effector mechanisms of the cross-linked immune cell.4 T-cell-engaging bsAb have been proven to be highly effective in inducing the lytic capacity of both CD4+ and CD8+ Teffs in vitro, in vivo and even in clinical trials and closely resemble signal cascades induced upon binding of a TCR to its target peptide/MHC complex.4, 5, 6

/pdf/cytotoxic-response-of-human-regulatory-t-cells-upon-t-cell-35v4d45grq.pdf

Cytotoxic response of human regulatory T cells upon T-cell receptor-mediated activation: a matter of purity.

This article summarises the presentations and discussions during a workshop on end-to-end protocols for the future Internet in June 2008. The aim of the workshop was to establish a dialogue at the interface between two otherwise fairly distinct communities working on future Internet protocols: those developing internetworking functions and those developing end-to-end transport protocols. The discussion established near-consensus on some of the open issues, such as the preferred placement of traffic engineering functionality, whereas other questions remained controversial. New research agenda items were also identified.

/pdf/dagstuhl-perspectives-workshop-on-end-to-end-protocols-for-10qfpmmple.pdf

Dagstuhl perspectives workshop on end-to-end protocols for the future internet

Compared to testbeds, the efficiency and accuracy of wireless networking simulations are constantly questioned by the network community. It is widely accepted today that the current network simulators are not able to fully represent the real wireless characteristics, especially at the physical (PHY) layer. This affects the trustability of simulation-based performance evaluations. On the other hand, testbed experiments require taking a tedious and time-consuming implementation path. This path could be significantly reduced by using realistic network simulators as a first step to test novel algorithms or protocols. Therefore, we took on the challenge of representing the link characteristics of the indoor testbed of the Berlin Open Wireless Lab (BOWL) project in the ns-3 simulator. Our extensive measurements study of the link characteristics, namely received signal strength (RSS), frame detection ratio (FDR) and frame error ratio (FER), produced several guidelines for modeling our testbed with satisfying accuracy in the simulator. More importantly, the proposed empirical models take into account several crucial properties related to the radio hardware and the environment, which are shown to have a significant impact on the simulation accuracy. We validate our model against testbed results and show that, unlike the existing models in ns-3, our model shows high agreement with the measurement results for any pair of nodes in the testbed.

/pdf/a-site-specific-indoor-link-model-for-realistic-wireless-s656x80x2l.pdf

Anja Feldmann

Papers

AS-Path Prepending: there is no rose without a thorn

HERO: hierarchical EMC-constrained routing

Cytotoxic response of human regulatory T cells upon T-cell receptor-mediated activation: a matter of purity.

Dagstuhl perspectives workshop on end-to-end protocols for the future internet

A site-specific indoor link model for realistic wireless network simulations