Showing papers by "Anja Feldmann published in 2015"

C3: cutting tail latency in cloud data stores via adaptive replica selection

Abstract: Achieving predictable performance is critical for many distributed applications, yet difficult to achieve due to many factors that skew the tail of the latency distribution even in well-provisioned systems. In this paper, we present the fundamental challenges involved in designing a replica selection scheme that is robust in the face of performance fluctuations across servers. We illustrate these challenges through performance evaluations of the Cassandra distributed database on Amazon EC2. We then present the design and implementation of an adaptive replica selection mechanism, C3, that is robust to performance variability in the environment. We demonstrate C3's effectiveness in reducing the latency tail and improving throughput through extensive evaluations on Amazon EC2 and through simulations. Our results show that C3 significantly improves the latencies along the mean, median, and tail (up to 3 times improvement at the 99.9th percentile) and provides higher system throughput.

Annoyed Users: Ads and Ad-Block Usage in the Wild

Abstract: Content and services which are offered for free on the Internet are primarily monetized through online advertisement. This business model relies on the implicit agreement between content providers and users where viewing ads is the price for the "free" content. This status quo is not acceptable to all users, however, as manifested by the rise of ad-blocking plugins which are available for all popular Web browsers. Indeed, ad-blockers have the potential to substantially disrupt the widely established business model of "free" content, currently one of the core elements on which the Web is built.In this work, we shed light on how users interact with ads. We show how to leverage the functionality of AdBlock Plus, one of the most popular ad-blockers to identify ad traffic from passive network measurements. We complement previous work, which focuses on active measurements, by characterizing ad-traffic in the wild, i.e., as seen in a residential broadband network of a major European ISP. Finally, we assess the prevalence of ad-blockers in this particular network and discuss possible implications for content providers and ISPs.

OpenSDWN: Programmatic Control overHome and Enterprise WiFi

Abstract: The quickly growing demand for wireless networks and the numerous application-specific requirements stand in stark contrast to today’s inflexible management and operation of WiFi networks. In this paper, we present and evaluate OPENSDWN, a novel WiFi architecture based on an SDN/NFV approach. OPENSDWN exploits datapath programmability to enable service differentiation and fine-grained transmission control, facilitating the prioritization of critical applications. OPENSDWN implements per-client virtual access points and per-client virtual middleboxes, to render network functions more flexible and support mobility and seamless migration. OPENSDWN can also be used to out-source the control over the home network to a participatory interface or to an Internet Service Provider.

OpenSDWN: programmatic control over home and enterprise WiFi

Abstract: The quickly growing demand for wireless networks and the numerous application-specific requirements stand in stark contrast to today's inflexible management and operation of WiFi networks. In this paper, we present and evaluate OpenSDWN, a novel WiFi architecture based on an SDN/NFV approach. OpenSDWN exploits datapath programmability to enable service differentiation and fine-grained transmission control, facilitating the prioritization of critical applications. OpenSDWN implements per-client virtual access points and per-client virtual middleboxes, to render network functions more flexible and support mobility and seamless migration. OpenSDWN can also be used to out-source the control over the home network to a participatory interface or to an Internet Service Provider.

Distilling the Internet's Application Mix from Packet-Sampled Traffic

Abstract: As the Internet continues to grow both in size and in terms of the volume of traffic it carries, more and more networks in the different parts of the world are relying on an increasing number of distinct ways to exchange traffic with one another. As a result, simple questions such as “What is the application mix in today’s Internet?” may produce non-informative simple answers unless they are refined by specifying the vantage point where the traffic is observed, the networks that are involved, or even the type of interconnection used.

Bispecific antibody releasing-mesenchymal stromal cell machinery for retargeting T cells towards acute myeloid leukemia blasts

Abstract: Bispecific antibodies (bsAbs) engaging T cells are emerging as a promising immunotherapeutic tool for the treatment of hematologic malignancies. Because their low molecular mass, bsAbs have short half-lives. To achieve clinical responses, they have to be infused into patients continously, for a long period of time. As a valid alternative we examined the use of mesenchymal stromal cells (MSCs) as autonomous cellular machines for the constant production of a recently described, fully humanized anti-CD33-anti-CD3 bsAb, which is capable of redirecting human T cells against CD33-expressing leukemic cells. The immortalized human MSC line SCP-1 was genetically modified into expressing bsAb at sufficient amounts to redirect T cells efficiently against CD33 presenting target cells, both in vitro and in an immunodeficient mouse model. Moreover, T cells of patients suffering from acute myeloid leukemia (AML) in blast crisis eliminated autologous leukemic cells in the presence of the bsAb secreting MSCs over time. The immune response against AML cells could be enhanced further by providing T cells an additional co-stimulus via the CD137-CD137 ligand axis through CD137L expression on MSCs. This study demonstrates that MSCs have the potential to be used as cellular production machines for bsAb-based tumor immunotherapy in the future.

Quo vadis Open-IX?

Abstract: The recently launched initiative by the Open-IX Association (OIX) to establish the European-style Internet eXchange Point (IXP)model in the US suggests an intriguing strategy to tackle a problem that some Internet stakeholders in the US consider to be detrimental to their business; i.e., a lack of diversity in available peering opportunities. We examine in this paper the cast of Internet stakeholders that are bound to play a critical role in determining the fate of this Open-IX effort. These include the large content and cloud providers, CDNs, Tier-1 ISPs, the well-established and some of the newer commercial datacenter and colocation companies, and the largest IXPs in Europe. In particular, we comment on these different parties' current attitudes with respect to public and private peering and discuss some of the economic arguments that will ultimately determine whether or not the currently pursued strategy by OIX will succeed in achieving the main OIX-articulated goal -- a more level playing field for private and public peering in the US such that the actual demand and supply for the different peering opportunities will be reflected in the cost structure.

Programming the Home and Enterprise WiFi with OpenSDWN

Abstract: The quickly growing demand for wireless networks and the numerous application-specific requirements stand in stark contrast to today's inflexible management and operation of WiFi networks In this paper, we present and evaluate OpenSDWN, a novel WiFi architecture based on an SDN/NFV approach OpenSDWN exploits datapath programmability to enable service differentiation and fine-grained transmission control, facilitating the prioritization of critical applications OpenSDWN implements per-client virtual access points and per-client virtual middleboxes, to render network functions more flexible and support mobility and seamless migration OpenSDWN can also be used to out-source the control over the home network to a participatory interface or to an Internet Service Provider

Evolution of Directed Triangle Motifs in the Google+ OSN

Abstract: 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).

Tregs activated by bispecific antibodies: Killers or suppressors?

Abstract: In recent years, bispecific antibodies (bsAb) have emerged as promising tools for a target-specific redirection of T cells in order to eliminate malignant cells. However, CD3-engaging constructs might also activate T regulatory cells (Tregs) present in the tumor microenvironment. Whether this has detrimental or beneficial effects for tumor therapy is still controversially discussed.

Quo vadis Open-IX? Trying to boost public peering in the US

Abstract: The recently launched initiative by the Open-IX Association (OIX) toestablishtheEuropean-styleInternet eXchange Point (IXP)model in the US suggests an intriguing strategy to tackle a problem that some Internet stakeholders in the US consider to be detrimental to their business; i.e., a lack of diversity in available peering opportunities. We examine in this paper the cast of Internet stakeholders that are bound to play a critical role in determining the fate of this Open-IX effort. These include the large content and cloud providers, CDNs, Tier-1 ISPs, the well-established and some of the newer commercial datacenter and colocation companies, and the largest IXPs in Europe. In particular, we comment on these different parties’ current attitudes with respect to public and private peering and discuss some of the economic arguments that will ultimately determine whether or not the currently pursued strategy by OIX will succeed in achieving the main OIX-articulated goal ‐ a more level playing field for private and public peering in the US such that the actual demand and supply for the different peering opportunities will be reflected in the cost structure.