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Inhalt des Dokuments

Talks, student talks, and other events of 2017

Wednesday, 13. December 2017

Managing Backpressure in Data Flow Models with scaling and re-partitioning
Speaker:
David Herzog

Type:
Masterstudent final talk
Time:
13 December 2017
11:00–12:00
Place:
MAR 4.033
Abstract:
It has become apparent that big streams of data (e.g. credit card transaction data) can only be processed in a timely manner with the use of multiple distributed machines. However, providing results in a timely manner in distributed streaming systems is difficult, because machines can vary in performance and the volume of ingested data often changes over time. In the commonly used data flow model items flow through a structure resembling a directed graph and are processed by the machines they pass. Items can accumulate in front of machines, which process items at a relatively low rate. This backpressure effects throughput and the processing time negatively.
We have created a backpressure model and identified backpressure patterns. Based on our model, we developed an algorithm, which identifies backpressure and its cause in a system and automatically chooses a mitigation technique based on the backpressure pattern.
Using the stream processing framework Apache Flink, we show that an implementation of our algorithm can effectively detect and mitigate backpressure. Further, we present instances where backpressure in Flink behaves unexpectedly real-world setting, since they can be counter-intuitive.

Thursday, 09. November 2017

Cloud 3.0
Speaker:
Dr. James Kempf (Ericsson Research)
Type:
Guest Talk
Time:
9 November 2017
13:00–14:00
Place:
MAR 4.033
Abstract:
In the last year, the international cloud research community has begun to define what the next generation of cloud management systems will be, generically designated as Cloud 3.0. At Ericsson Research, we believe that the next generation of cloud management software must cater to the needs of the application developer. The primary use case is development environments for cloud native applications, so that developers don't just deploy into the cloud, they also develop there. Support for cloud native development environments should erase the difference between the developer's laptop and the cloud. Infrastructure programming and networking must disappear to remove the requirement for developers to deal with complexity. On the data center management side, the cloud management system should be fully distributed to avoid single points of failure and to make cloud management scale down as well as up. Analytics and policy control should be tightly interwoven with resource management, and simpler for the developer to use. In this talk, I will discuss the architectural principles, system components, and key differentiators of the Cloud 3.0 platform we are building at Ericsson Research.
Bio:
Dr. James Kempf graduated from University of Arizona with a Ph.D. in Systems Engineering in 1984 and immediately went to work in Silicon Valley. Prior to his current position, Dr. Kempf spent 3 years at HP, 13 years at Sun Microsystems, primarily in research, and 8 years at Docomo Labs USA as a Research Fellow. Dr. Kempf is the holder of 18 patents, and the author of many technical papers and 3 books, the latest of which, "Wireless Internet Security:Architecture and Protocols" was published by Cambridge University Press in 2008.

Tuesday, 24. October 2017

On Compact Decomposable Linear Programming Formulations for the Virtual Network Embedding Problem
Speaker:
Elias Döhne
Type:
Masterstudent introductory talk
Time:
24 October 2017
14:15–15:00
Place:
MAR 4.023
Abstract:
The Virtual Network Embedding Problem (VNEP) considers the efficient allocation of resources distributed in a substrate network to one or more request networks. A new approximation algorithm for the VNEP with general substrate and request network topologies has recently been developed based on a novel linear programming (LP) formulation.
The LP formulation for a single request is based on an acyclic orientation of the request graph. The size and therefore the solving time of this LP formulation depends on the newly defined "width" of the chosen orientation. Hence, to compute LP solutions quickly, choosing an orientation of minimum width is of crucial importance. As was shown recently, finding the orientation of minimum width is a NP-hard problem.
In this thesis, we investigate three methods to obtain orientations of small width.
1. We study heuristics for finding orientations of small width according to the original definition of width.
2. We introduce the notion of multiple roots for the orientation and study the impact as well as algorithms for deciding where to root orientations.
3. We introduce the notion of hierarchical edge bags which can significantly reduce the size of the formulation and study the computational hardness of finding the best hierarchy.
We plan a theoretical investigation of these approaches, along with an implementation and practical evaluation of corresponding algorithms.

Wednesday, 06. September 2017

Measurement and Characterization of Address Blocks in IPv4 and IPv6
Speaker:
Shihab Karim
Type:
Masterstudent introductory talk
Time:
6 September 2017
14:00–15:00
Place:
MAR 4.033
Abstract:
Although IPv6 is the designated successor of IPv4, the conditions during its deployment are very much different. While the usage of IPv4 began with the Internet at an early stage of developement, IPv6 is being introduced to a mature and diverse Internet. Despite the IPv4 address exhaustion, the global IPv4 routing table is still growing. There are some explanations among which are multi-homing, load balancing, or prefix delegations. While the IPv6 routing table is growing as well, it contains less prefixes.



In order to better understand the evolution of the routing tables this work analyses the usage of address blocks, from the allocation to the announcement via BGP, and characterize and compare both routing eco systems, IPv4 and IPv6.

Monday, 14. August 2017

Bringing multi-tenancy to WiFi HotSpot networks following a joint SDN and NFV approach
Speaker:
Raphael Lisicki

Type:
Masterstudent final talk
Time:
14 August 2017
11:00–12:00
Place:
MAR 4.033
Abstract:
The increasing demand for flexibility in WiFi network deployments along with more stringent requirements on performance and security stand in stark contrast to today’s ossified and expensive WiFi architecture. In particular, today’s WiFi consists of a large number of control and data plane network functions that are either bundled into a single proprietary WiFi controller or they are distributed across the networks and run on the WiFi Access Points. In this thesis, we present the notion of a wireless switch and decomposition of some of the WiFi MAC functionality which enables the deployment of flexible WiFi architectures. Specifically, we present a way to decouple the client’s association, authentication, and cryptography from the WiFi device so that these function can be placed where (and when) they are most useful. This makes it possible to use untrusted access points in a trusted way without client-side modifications.

Friday, 11. August 2017

Improving and Interpreting Machine Learning Algorithms with Applications
Speaker:
Marina Marie-Claire Vidovic, M.Sc.
Type:
Wissenschaftliche Aussprache zur Erlangung akademischen Grades „Doktor der Naturwissenschaften (Dr.rer.nat.)“
Time:
11 August 2017
13:00–15:00
Place:
MAR 4.033
Der Promotionsausschuss setzt sich wie folgt zusammen:

Frau Prof. Feldmann, Ph.D.

Gutachter:

Prof. Dr. Müller

Prof. Dr. Farina (Imperial College London, UK)

Prof. Dr. Blankertz

Die Dissertation und die Gutachten können von Berechtigten nach § 8 Abs. 1 der Promotionsordnung in der Fakultätsverwaltung eingesehen werden. Die wissenschaftliche Aussprache ist universitätsöffentlich.

Tuesday, 08. August 2017

Transport Notes from Prague - IETF99 Report
Speaker:
Philipp Tiesel
Type:
Project group meeting (Projektgruppentreffen, PGT)
Time:
08 August 2017
15:00 - 16:00
Place:
MAR 4.023

Thursday, 03. August 2017

Finding Very Damaging Needles in Very Large Haystacks
Speaker:
Vern Paxson (UC Berkeley) see bio below.
Type:
Invited Talk
Time:
03 August 2017
16:00-18:00
Place:
MA 042
Abstract:

Many of the most costly security compromises that enterprises suffer manifest as tiny trickles of behavior hidden within an ocean of other site activity. This talk exams the problem of developing robust detectors for particular forms of such activity. The themes include research pitfalls, the crucial need to leverage domain knowledge in an apt fashion, and why machine learning is very difficult to effectively apply for such detection.
Bio:

Vern Paxson is a Professor of Electrical Engineering and Computer Sciences at UC Berkeley. He also leads the Networking and Security Group at the International Computer Science Institute in Berkeley, and for decades held an appointment as a Staff Scientist at the Lawrence Berkeley National Laboratory. His research focuses heavily on measurement-based analysis of network activity and Internet attacks. He works extensively on high performance network monitoring, detection algorithms, cybercrime, and countering censorship and abusive surveillance. In 2006 he was inducted as a Fellow of the Association for Computing Machinery (ACM). In 2011 he received ACM's SIGCOMM Award, which recognizes lifetime contribution to the field of communication networks, "for his seminal contributions to the fields of Internet measurement and Internet security, and for distinguished leadership and service to the Internet community." His measurement work has also been recognized by ACM's Grace Murray Hopper Award and by the 2015 IEEE Internet Award. He co-founded Corelight, a company that provides commercial-grade products for the "Bro" network monitoring system that he created and has advanced through his research for many years. He currently serves as Corelight's Chief Scientist.

Wednesday, 02. August 2017

Empirical Analysis of the Effects and the Mitigation of IPv4 Address Exhaustion
Speaker:
Philipp Richter, M.Sc.
Type:
Wissenschaftliche Aussprache zur Erlangung akademischen Grades „Doktor der Ingenieurwissenschaften“
Time:
02 August 2017
10:00–12:00
Place:
MAR 4.064
Der Promotionsausschuss setzt sich wie folgt zusammen:

Prof. Dr.-Ing. Möller

Gutachter:

Frau Prof. Feldmann, Ph.D.

Prof. Paxson, Ph.D. (University of California, USA)

Prof. Dr. Uhlig (Queen Mary University of London, UK)

Die Dissertation und die Gutachten können von Berechtigten nach § 8 Abs. 1 der Promotionsordnung in der Fakultätsverwaltung eingesehen werden. Die wissenschaftliche Aussprache ist universitätsöffentlich.

Tuesday, 25. July 2017

Competitive Online Virtual Cluster Embeddings
Speaker:
Feras Fattohi
Type:
Masterstudent introductory talk
Time:
25 July 2017
15:00–16:00
Place:
MAR 4.033
Abstract:
Cloud providers offer an abundant amount of computational and network resources to tenants. Recently, researchers have focused on guaranteeing network performance (Quality-of-Service) inside the data center to improve the predictability of services. In particular, the virtual cluster abstraction has arisen as a simple model for services in the cloud. While related work mostly considers online algorithms for embedding virtual clusters inside data centers, no competetive online algorithms are known thus far. Competetiveness here refers to a performance guarantee on the achieved overall revenue by the cloud provider compared to the optimal (offline) solution. Accordingly, the objective of the thesis is to develop and evaluate competitive online virtual cluster embedding algorithms. In particular, from a theoretic side obtaining competetive algorithms that minimize resource violations are seeked while from a practical side, the impact of more advanced admission control schemes will be studied in computional evaluations.

Tuesday, 25. July 2017

Extending Big Data Analytics to the Wide-Area
Speaker:
David Herzog
Type:
Masterstudent project talk
Time:
25 July 2017
14:00–15:00
Place:
MAR 4.033
Abstract:
David Herzog will present the result of his Master project on accomodating Flink in the wide-area. He focused on detecting and understanding load imbalances between Flink operators.

Tuesday, 20. June 2017

Improving Voice over GNUnet
Speaker:
Christian Ulrich (TU Berlin bachelor student)
Type:
Bachelorstudent final talk
Time:
20 June 2017
14:00–15:00
Place:
MAR 4.033
Abstract:
In contrast to ubiquitous cloud-based solutions the telephony application GNUnet conversation provides fully-decentralized, secure voice communication and thus impedes mass surveillance. The aim of this thesis is to investigate why GNUnet conversation currently provides poor Quality of Experience under typical wide area network conditions and to propose optimization measures. After automating network shaping and establishing arbitrary topologies of GNUnet peers multiple GNUnet components were prepared for delay measurements. Network, cryptography and audio codec delays were measured and the transmitted speech was recorded. An analysis of the measurement results and a subjective assessment of the speech recordings revealed that extreme outliers occur in most scenarios and impair QoE. Moreover it was shown that GNUnet conversation introduces a large delay that confines the environment in which good QoE is possible. In the measurement environment at least 23 ms always ocurred of which large parts are were caused by cryptography. It was shown that optimization in the cryptography part and other components are possible. Finally the conditions for currently reaching good QoE were determined and ideas for further investigations were presented.

Friday, 16. June 2017

An Empirical Evaluation of Misconfiguration in Internet Services
Speaker:
Tobias Fiebig, M.Sc.
Type:
Wissenschaftliche Aussprache zur Erlangung akademischen Grades „Doktor der Ingenieurwissenschaften“
Time:
16 June 2017
14:00–16:00
Place:
MAR 4.033
Der Promotionsausschuss setzt sich wie folgt zusammen:

Prof. Dr.-Ing. Möller

Gutachter:

Frau Prof. Feldmann, Ph.D.

Prof. Dr. Seifert

Prof. Dr. Uhlig (Queen Mary, University of London)

Die Dissertation und die Gutachten können von Berechtigten nach § 8 Abs. 1 der Promotionsordnung in der Fakultätsverwaltung eingesehen werden. Die wissenschaftliche Aussprache ist universitätsöffentlich.

Friday, 09. June 2017

Understanding and Mitigating Packet Corruption in Data Center Networks
Speaker:
Klaus-Tycho Foerster (Aalborg University)
Type:
Guest Talk
Time:
9 June 2017
16:30–17:00
Place:
MAR 4.013
Abstract:
We take a comprehensive look at packet corruption, a significant yet overlooked source of packet loss that degrades application performance in data center networks. By studying 350K links across 15 production data centers, we find that the extent of corruption losses is similar to congestion losses.

Based on these observations, we developed CorrOpt, a new system to mitigate corruption. To minimize corruption losses, it intelligently selects which corrupting links can be safely disabled, while ensuring that each top-of-rack switch has a minimum number of paths to reach other switches.

Trace-based simulations and data analysis from this deployment show that, compared to the current state of art, CorrOpt can reduce corruption losses by three to six orders of magnitude.

Joint work with Danyang Zhuo (University of Washington); Monia Ghobadi and Ratul Mahajan (Microsoft Research); Arvind Krishnamurthy and Thomas Anderson (University of Washington)

Friday, 09. June 2017

Concurrent self-adjusting distributed tree networks
Speaker:
Bruna Peres
Type:
Guest Talk
Time:
9 June 2017
16:00–16:30
Place:
MAR 4.013
Abstract:
SplayNets are a distributed generalization of the classic splay tree data structures. Given a set of communication requests and a network comprised of n nodes, such that any pair of nodes is capable of establishing a direct connection, the goal is to dynamically find and adjust a (locally routable) tree topology which optimizes the routing cost for the given communication pattern and minimizes the topological reconfiguration costs. We present the first concurrent implementation of such self-adjusting SplayNets. Analytical results show that our proposed algorithm prevents loops and deadlocks from occurring between concurrent rotations. We compute the total amortized average cost of a splay request in number of rounds and number of time-slots.

Tuesday, 06. June 2017

Security Misconfiguration in Distributed Systems
Speaker:
Tobias Fiebig, M.Sc.
Type:
Talk
Time:
06 June 2017
10:00–10:40
Place:
MAR 6.011
Abstract:
Incidents like the one where an attack on the thermostats of a Finnish housing complex shut down the central heating during winter are the motivation of this talk. While such attacks become more frequent, we find that they are not commonly enabled by highly-sophisticated exploits. Instead, they are made possible by simple errors, like accidentally exposing Industry 4.0 systems on the Internet, sometimes even without authentication.

We find that these errors are usually generally known, and could have been easily mitigated. However, with the increasing adoption of IPv6, classical mitigation strategies reach their limits. Hence, we present new approaches that make classical mitigation strategies applicable for IPv6. Yet, preventing misconfiguration and simple errors before they occur is the more root-cause directed approach to the problem.

Therefore, we conclude the talk with the first results of our ongoing research that uncovers why operators make these simple errors, and how they could be prevented. Furthermore, we explore future research directions transferring our results from the field of system deployment to system design and implementation.

Tuesday, 30. May 2017

Scalable Automatic Topology Generation in SDN
Speaker:
Mengchen Shi
Type:
Masterstudent final talk
Time:
30 May 2017
15:00–16:00
Place:
MAR 4.033
Abstract:
Software-Defined Networks (SDNs) have been an area of interest among researchers from academia and industry. SDNs, however, also introduce new challenges, for example researchers work under strict time constraints and need to conduct frequent experiments to verify their ideas on scalable simulation of real-life topologies. The challenge is twofold: first, the researchers need to manually generate the topologies and second, manually configure the devices in the generated topologies to enable routing protocols. We demonstrate two novel tools, namely, Topology Generator and Enhanced Automatic Configuration Route-Flow (EACRF), which automatically generate the custom scalable topologies at the SDN data plane and configure routing protocols like BGP and OSPF, at the SDN control plane, in a seamless fashion in quick time. EACRF is an enhancement of RouteFlow which can be used in conjunction with Topology Generator or independently.

Friday, 19. May 2017

Strengthening System Security on the ARMv7 Processor Architecture with Hypervisor-based Security Mechanisms
Speaker:
Julian Vetter, M.Sc.
Type:
Wissenschaftliche Aussprache zur Erlangung akademischen Grades „Doktor der Ingenieurwissenschaften“
Time:
19 May 2017
10:30–12:00
Place:
TEL Auditorium 3
Der Promotionsausschuss setzt sich wie folgt zusammen:

Frau Prof. Feldmann, Ph.D.

Gutachter:

Prof. Dr. Seifert

Prof. Dr. Margraf (FU Berlin)

Prof. Dr. Gueron (University of Haifa, Israel)

Die Dissertation und die Gutachten können von Berechtigten nach § 8 Abs. 1 der Promotionsordnung in der Fakultätsverwaltung eingesehen werden. Die wissenschaftliche Aussprache ist universitätsöffentlich.

Monday, 09. May 2016

Adaptive Multipath TCP Path Management Using SDN in Data Center Networkss
Speaker:
Imed Bezahaf
Type:
Masterstudent final talk
Time:
9 May 2017
14:00–15:00
Place:
MAR 4.033
Abstract:
Intra-data center transfers are becoming more crucial due to the steady growing number of large scale Internet applications, [1], hence providing a high throughput for these applications is a priority. Consequently, Multi-Path TCP (MPTCP) can be an effective approach towards this goal. Indeed, MPTCP provides the ability to split a TCP stream into multiple flows (subflows) by enabling the simultaneous use of different network interfaces. This provides better throughput and helps to achieve maximization of the network utilization. However, in practice, performance limitations arise with the current MPTCP implementation. Given that MPTCP is a transport layer protocol, it lacks in having control over the paths assigned to subflows. As a matter of fact, the path selection for MPTCP traffic heavily relies on the routing decisions. Although, the default routing generally takes all the traffic between a source and a destination through a best metric path (for instance: shortest path). This leads subflows to collide with each other, resulting into a bandwidth contention therefore decreasing the global performance.

This thesis tackles this issue by exploring a new path management paradigm for MPTCP subflows using a Software Defined Networking (SDN) approach. Instead of having a traditional routing behavior, our SDN controller proposes a traffic forwarding concept based on an “adaptive bandwidth aware routing”. Using topology information and monitoring, path selection decisions are made to provide a better throughput. A set of evaluations was conducted using the network emulator Mininet. The measurements from our experiments indicated favorable results and show better performances than current routing mechanisms.

Tuesday, 26. April 2016

Multi-Homed on a single link Exploiting IPv6 flexibility to enable MultiAccess
Speaker:
Bernd May
Type:
Masterstudent final talk
Time:
11 April 2017
15:00–16:00
Place:
MAR 4.033
Abstract:
Smart mobile devices with WWAN internet access have become ubiquitous. These de- vices can share this access and act as gateways in existing computer networks, i.e. via tethering. If a computer already has a connection to the internet via an existing ac- cess gateway, it effectively becomes multi-homed, enabling the use of both gateways at the same time. Unfortunately, barring the use of Multipath TCP, common applications rarely avail themselves of this opportunity. In addition, tethering is usually combined with a single computer device only, even though the additional access gateway could potentially share its internet connection with multiple devices in the same network, e.g., via WIFI. Due to lack of network auto-configuration support, most computer devices can not handle additional access gateways automatically, preventing widespread use of this technology.

Therefore this thesis evaluates the standard network auto-configuration protocols DHCPv6 and Stateless Address Autoconfiguration for the possibility to provide support for multiple access gateways in the same network. In addition it provides a proof of concept enhancement to the DHCPCD client software, enabling multi-access host configuration via policy routing. The thesis also contains a multiple recursive DNS resolver configuration as a sample solution for common applications benefiting from multiple access gateways.

Wednesday, 22. March 2017

Data Aggregation in Apache Flink
Speaker:
Karl-Philipp Wulfert (TU Berlin bachelor student)
Type:
Bachelorstudent final talk
Time:
22 March 2017
09:30–10:30
Place:
MAR 4.033
Abstract:
This thesis evaluates different approaches to implement a Top-K calculation in Apache Flink with distributed data sets. The goal is to stay close to the dataflow paradigm of the framework and to use its provided functions and patterns to build implementations that are especially low in bandwidth consumption and other possible overheads. Because that proved to be too restrictive the goal was to enhance the framework or at least push the boundaries a little further to explore different and more possibilities to achieve efficient implementations. The different approaches are then evaluated: On the one hand how invasive the changes are that were made to the original framework and on the other hand how efficient they are. Finally the results of the evaluation is concluded and work to develop the framework further is proposed to enable better solutions.

Tuesday, 14. March 2017

Approximating Virtual Network Embeddings using Randomized Rounding
Speaker:
Matthias Rost
Type:
Project group meeting (Projektgruppentreffen, PGT)
Time:
14 March 2017
15:00 - 16:00
Place:
MAR 4.033

Tuesday, 07. March 2017

Bridging The Gap: Towards Rigorous Data Plane Verification
Speaker:
Apoorv Shukla
Type:
Project group meeting (Projektgruppentreffen, PGT)
Time:
07 March 2017
15:00 - 16:00
Place:
MAR 4.033
Abstract:
The operation of software-defined networks relies on a logically centralized controller, which is assumed to have a consistent view of the data plane. Providing such a consistent data plane view to the controller, however, is challenging: the data plane is subject to continuous changes for various reasons, and due to the decoupling of the control plane from the data plane, the former is not always notified about the events affecting the data plane configuration. This can result in reduced performance or even violations of security policies. This paper identifies and describes a number of scenarios leading to an incorrect view of the data plane at the controller. Motivated by these inconsistencies, we present a systematic approach, VeriTag, for finding inconsistencies in the data plane. VeriTag leverages a combined control and data plane methodology, systematically comparing the control plane expected with the data plane actual state. We show that our approach can detect important inconsistencies, such as misconfigurations, hidden flow rules, and software or hardware bugs, which are not covered by prior work. Using a prototype implementation, we demonstrate that our approach also comes with low overheads.

Tuesday, 28. February 2017

PGT by Balakrishnan Chandrasekaran
Speaker:
Balakrishnan Chandrasekaran
Type:
Project group meeting (Projektgruppentreffen, PGT)
Time:
28 February 2017
15:00 - 16:00
Place:
MAR 4.033

Tuesday, 07. February 2017

Masterstudent introductory talk by Sebastian Lohff
Speaker:
Sebastian Lohff
Type:
Masterstudent introductory talk
Time:
07 February 2017
15:00–16:30
Place:
MAR 4.033
Abstract:
 The Internet is one of the biggest communication networks in the world.  Inter-domain routing via BGP plays a big part in the success of the Internet.  But it is a hard topic to grasp and successfully implement without getting first-hand knowledge in operating a BGP-based network. This thesis presents a self-made testbed using off-the-shelf components to create an Internet-like infrastructure that aims to represent as many features of the real-world Internet as possible. The thesis describes how this testbed was created, what its goals are and what infrastructure and software were written to simulate different aspects of the Internet.  Services like DNS are also taken in consideration, resulting in a more holistic approach to fullfil the goal of recreating an Internet ''ecosystem''. Furthermore, to compare the testbed to its real couterpart, a set of attributes outlining the Internet are discussed and the testbed is evaluated within this context. Additionally the thesis provides a comparison to other inter-domain routing testbeds.

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