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

With the recent IPv4 address exhaustion, many networks can no longer rely on requesting additional IPv4 addresses space. They resort to new ways to obtain addresses: buying and leasing. In this paper, we first shed light on the recent economic trends of the IPv4 buying market by augmenting transfer statistics with public and private pricing information from four large IPv4 brokers. We infer the size of the IPv4 leasing market through two different data sources: routing information observed from BGP collectors and RDAP databases operated by the Regional Internet Registries. We find that neither of those sources alone is capable of estimating the full market size. We relate our findings to discussions with 13 IPv4 brokers and summarize how networks handle their demand for obtaining IPv4 addresses in 2020.

https://dl.acm.org/doi/pdf/10.1145/3386367.3431301

When wells run dry: the 2020 IPv4 address market

Online Social Networks (OSN) are among the most popular applications in today's Internet. Decentralized online social networks (DOSNs), a special class of OSNs, promise better privacy and autonomy than traditional centralized OSNs. However, ensuring availability of content when the content owner is not online remains a major challenge. In this paper, we rely on the structure of the social graphs underlying DOSN for replication. In particular, we propose that friends, who are anyhow interested in the content, are used to replicate the users content. We study the availability of such natural replication schemes via both theoretical analysis as well as simulations based on data from OSN users. We find that the availability of the content increases drastically when compared to the online time of the user, e. g., by a factor of more than 2 for 90% of the users. Thus, with these simple schemes we provide a baseline for any more complicated content replication scheme.

/pdf/revisiting-content-availability-in-distributed-online-social-4o72atvl8d.pdf

Revisiting Content Availability in Distributed Online Social Networks

Speech quality in Next Generation Mobile Networks (NGMN) is critical. Accordingly, we analyze in this paper, how the quality estimation provided by wideband PESQ, a signal-based speech quality prediction model, differs from the user perception. We find that the model underestimates the auditory quality in certain NGMN conditions: 1) wideband-narrowband speech codec switching, 2) speech signal fading during codec switching, and 3) talk-spurt internal time-shifting due to jitter buffer instability. By pointing out the impact of these degradations on the speech signal, this paper contributes to potential improvements and adaptation of the wideband PESQ model for NGMNs.

Understanding Signal-Based Speech Quality Prediction in Future Mobile Communications

Motifs are a fundamental building block and distinguishing feature of networks. While characteristic motif distribution have been found in many networks, very little is known today about the evolution of network motifs. This paper studies the most important motifs in social networks, triangles, and how directed triangle motifs change over time. Our chosen subject is one of the largest Online Social Networks, Google+. Google+ has two distinguishing features that make it particularly interesting: (1) it is a directed network, which yields a rich set of triangle motifs, and (2) it is a young and fast evolving network, whose role in the OSN space is still not fully understood. For the purpose of this study, we crawled the network over a time period of six weeks, collecting several snapshots. We find that some triangle types display significant dynamics, e.g., for some specific initial types, up to 20% of the instances evolve to other types. Due to the fast growth of the OSN in the observed time period, many new triangles emerge. We also observe that many triangles evolve into less-connected motifs (with less edges), suggesting that growth also comes with pruning. We complement the topological study by also considering publicly available user profile data (mostly geographic locations). The corresponding results shed some light on the semantics of the triangle motifs. Indeed, we find that users in more symmetric triangle motifs live closer together, indicating more personal relationships. In contrast, asymmetric links in motifs often point to faraway users with a high in-degree (celebrities).

/pdf/evolution-of-directed-triangle-motifs-in-the-google-osn-4vmrq2vphy.pdf

Evolution of Directed Triangle Motifs in the Google+ OSN

A method of engineering traffic within a network includes configuring and controlling routing within the network and steering traffic through the network, wherein the steering of the traffic through the network is optimized based on routing control and configuration by evaluating interior gateway protocol weights, label switch paths within multiprotocol label switching and/or border gateway protocol properties. The method further includes obtaining an ingress point at which content enters the network and obtaining an egress point at which content exits the network. The steering of the traffic through the network is optimized based on routing control and configuration by evaluating the ingress point and the egress point.

Anja Feldmann

Papers

When wells run dry: the 2020 IPv4 address market

Revisiting Content Availability in Distributed Online Social Networks

Understanding Signal-Based Speech Quality Prediction in Future Mobile Communications

Evolution of Directed Triangle Motifs in the Google+ OSN

Network traffic engineering