Florian Wohlfart, M.Sc.

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Research

Internet Measurement

Carrier Grade NAT detection: We performed a large-scale measurement study of the deployment and behavior of Carrier Grade NAT (CGN) in ISP networks. As one measurement methodology we integrated a traceroute-like approach for stateful middlebox detection into the Netalyzr network troubleshooting tool. We found a large variability in the dimensioning, configuration, and placement of CGNs and observe that CGN deployments have a larger impact on connectivity compared to CPE NAT devices.

Browser-based network measurement: With the implementation of WebRTC all major web browsers now come with powerful networking functionality built-in. We want to find out if we can utilize web browsers for crowd-sourced measurement of network connectivity, performance, and middleboxes on different layers and also evaluate how reliable these measurements are. Currently, we are beta-testing a browser-based demo of the Netalyzr network troubleshooting tool.

TLS proxy detection: Previous measurement studies of TLS interception found a non-negligible percentage of TLS interception. We implemented a measurement tool that performs a range of different TLS handshakes to detect and analyze TLS proxies. Our approach goes beyond the state-of-the-are in that it varies the TLS handshake (e.g. SNI value) aiming to trigger selective TLS proxies.

Content Distribution

Akamai operates a global, highly distributed, and well-connected serving infrastructure. In our paper (to appear) we analyze the AS-level connectivity fabric of Akamai's platform paying special attention to deployments in guest networks that host Akamai machines. In addition, we examine performance data from Akamai's server-side logs and find a that peering decisions matter for performance.

Performance of Software-based Packet Processing

Performance measurements of networking devices only represent a current snapshot of a specific configuration. We built tools to improve and automate network performance testing such that we can easily repeat measurements and explore large parameter spaces. This includes documentation of our hardware setup and software configuration, such that other researchers can reproduce our measurements.

Teaching

Publications

2018-01-01 Florian Wohlfart, Nikolaos Chatzis, Caglar Dabanoglu, Georg Carle, Walter Willinger, “Leveraging Interconnections for Performance: The Serving Infrastructure of a Large CDN,” in SIGCOMM, 2018, pp. 206–220. [Pdf] [Bib]
2018-01-01 Sebastian Gallenmüller, Dominik Scholz, Florian Wohlfart, Quirin Scheitle, Paul Emmerich, Georg Carle, “High-Performance Packet Processing and Measurements (Invited Paper),” in 10th International Conference on Communication Systems & Networks (COMSNETS 2018), Bangalore, India, Jan. 2018. [Pdf] [Bib]
2017-11-01 Patricia Callejo, Connor Kelton, Narseo Vallina-Rodriguez, Rubén Cuevas, Oliver Gasser, Christian Kreibich, Florian Wohlfart, Ángel Cuevas, “Opportunities and Challenges of Ad-based Measurements from the Edge of the Network,” in Proc. of the 16th ACM Workshop on Hot Topics in Networks, Nov. 2017. [Pdf] [Bib]
2017-07-01 Paul Emmerich, Daniel Raumer, Sebastian Gallenmüller, Florian Wohlfart, Georg Carle, “Throughput and Latency of Virtual Switching with Open vSwitch: A Quantitative Analysis,” Journal of Network and Systems Management, Jul. 2017. [DOI] [Bib]
2017-05-01 Wolfgang Hahn, Borislava Gajic, Florian Wohlfart, Daniel Raumer, Paul Emmerich, Sebastian Gallenmüller, Georg Carle, “Feasibility of Compound Chained Network Functions for Flexible Packet Processing,” in International Workshop on 5G Enabling Technologies for the Internet of Things (GET-IoT) at the 23rd European Wireless (EW2017), Dresden, Germany, May 2017. [Pdf] [Bib]
2016-11-01 Philipp Richter, Florian Wohlfart, Narseo Vallina-Rodriguez, Mark Allman, Randy Bush, Anja Feldmann, Christian Kreibich, Nicholas Weaver, Vern Paxson, “A Multi-perspective Analysis of Carrier-Grade NAT Deployment,” in Proceedings of the 2016 ACM on Internet Measurement Conference, New York, NY, USA, Nov. 2016, pp. 215–229. [Url] [Pdf] [DOI] [Bib]
2016-10-01 Daniel Raumer, Sebastian Gallenmüller, Paul Emmerich, Lukas Märdian, Florian Wohlfart, Georg Carle, “Efficient Serving of VPN Endpoints on COTS Server Hardware,” in 2016 IEEE 5th tnternational Conference on Cloud Networking (CloudNet’16), Pisa, Italy, Oct. 2016. [Pdf] [Bib]
2016-07-01 Daniel Raumer, Sebastian Gallenmüller, Florian Wohlfart, Paul Emmerich, Patrick Werneck, Georg Carle, “Revisiting Benchmarking Methodology for Interconnect Devices,” in The Applied Networking Research Workshop 2016 (ANRW ’16), Berlin, Germany, Jul. 2016. [Pdf] [Bib]
2015-10-01 Paul Emmerich, Sebastian Gallenmüller, Daniel Raumer, Florian Wohlfart, Georg Carle, “MoonGen: A Scriptable High-Speed Packet Generator,” in Internet Measurement Conference (IMC) 2015, IRTF Applied Networking Research Prize 2017, Tokyo, Japan, Oct. 2015. [Pdf] [Bib]
2015-09-01 Daniel Raumer, Florian Wohlfart, Dominik Scholz, Georg Carle, “Performance Exploration of Software-based Packet Processing Systems,” in Proceedings of Leistungs-, Zuverlässigkeits- und Verlässlichkeitsbewertung von Kommunikationsnetzen und Verteilten Systemen, 6. GI/ITG-Workshop MMBnet 2015, Hamburg, Germany, Sep. 2015. [Pdf] [Bib]
2015-09-01 Torsten Runge, Daniel Raumer, Florian Wohlfart, Bernd E. Wolfinger, Georg Carle, “How Do Multiple Network Cards Influence the Software Router Performance?,” in Proceedings of Leistungs-, Zuverlässigkeits- und Verlässlichkeitsbewertung von Kommunikationsnetzen und Verteilten Systemen, 6. GI/ITG-Workshop MMBnet 2015, Hamburg, Germany, Sep. 2015. [Pdf] [Bib]
2015-07-01 Paul Emmerich, Daniel Raumer, Alexander Beifuß, Lukas Erlacher, Florian Wohlfart, Torsten M. Runge, Sebastian Gallenmüller, Georg Carle, “Optimizing Latency and CPU Load in Packet Processing Systems,” in International Symposium on Performance Evaluation of Computer and Telecommunication Systems (SPECTS 2015), Chicago, IL, USA, Jul. 2015. [Pdf] [Bib]
2015-06-01 Viktor Goldberg, Florian Wohlfart, Daniel Raumer, “Datacenter Network Virtualization in Multi-Tenant Environments,” in 8. DFN-Forum Kommunikationstechnologien, Jun. 2015. [Pdf] [Bib]
2015-05-01 Sebastian Gallenmüller, Paul Emmerich, Florian Wohlfart, Daniel Raumer, Georg Carle, “Comparison of Frameworks for High-Performance Packet IO,” in ACM/IEEE Symposium on Architectures for Networking and Communications Systems (ANCS 2015), Oakland, CA, USA, May 2015. [Pdf] [Bib]
2015-04-01 Torsten M. Runge, Daniel Raumer, Florian Wohlfart, Bernd E. Wolfinger, Georg Carle, “Towards Low Latency Software Routers,” Journal of Networks (JNW), Vol 10, No 4, Apr. 2015. [Pdf] [Bib]
2015-04-01 Paul Emmerich, Daniel Raumer, Florian Wohlfart, Georg Carle, “Assessing Soft- and Hardware Bottlenecks in PC-based Packet Forwarding Systems,” in Fourteenth International Conference on Networks (ICN 2015), Best Paper Award, Barcelona, Spain, Apr. 2015. [Pdf] [Bib]
2015-03-01 Alexander Beifuß, Daniel Raumer, Paul Emmerich, Torsten M. Runge, Florian Wohlfart, Bernd E. Wolfinger, Georg Carle, “A Study of Networking Software Induced Latency,” in 2nd International Conference on Networked Systems 2015 (NetSys’15), Cottbus, Germany, Mar. 2015. [Pdf] [Bib]
2015-01-01 Syed Naveed Rizvi, Daniel Raumer, Florian Wohlfart, Georg Carle, “Towards Carrier Grade SDNs,” Journal of Computer Networks, 2015. [Pdf] [Bib]
2014-12-01 Paul Emmerich, Daniel Raumer, Florian Wohlfart, Georg Carle, “A Study of Network Stack Latency for Game Servers,” in 13th Annual Workshop on Network and Systems Support for Games (NetGames’14), Nagoya, Japan, Dec. 2014. [Pdf] [Bib]
2014-10-01 Paul Emmerich, Daniel Raumer, Florian Wohlfart, Georg Carle, “Performance Characteristics of Virtual Switching,” in 2014 IEEE 3rd International Conference on Cloud Networking (CloudNet’14), Luxembourg, Oct. 2014. [Pdf] [Bib]
2014-07-01 Torsten Meyer, Daniel Raumer, Florian Wohlfart, Bernd E. Wolfinger, Georg Carle, “Low latency Packet Processing in Software Routers,” in International Symposium on Performance Evaluation of Computer and Telecommunication Systems (SPECTS 2014), Best Paper Award, Monterey, CA, USA, Jul. 2014. [Pdf] [Bib]
2014-03-01 Torsten Meyer, Florian Wohlfart, Daniel Raumer, Bernd E. Wolfinger, Georg Carle, “Validated Model-Based Prediction of Multi-Core Software Router Performance,” Praxis der Informationsverarbeitung und Kommunikation (PIK), vol. 37.2, pp. 93–107, Mar. 2014. [Pdf] [Bib]
2013-12-01 Andreas Müller, Florian Wohlfart, Georg Carle, “Analysis and Topology-based Traversal of Cascaded Large Scale NATs,” in HotMiddlebox: ACM CoNEXT Workshop on Hot Topics in Middleboxes and Network Function Virtualization, Santa Barbara, CA, USA, Dec. 2013. [Pdf] [Bib]
2013-09-01 Torsten Meyer, Florian Wohlfart, Daniel Raumer, Bernd E. Wolfinger, Georg Carle, “Measurement and Simulation of High-Performance Packet Processing in Software Routers,” in Proceedings of Leistungs-, Zuverlässigkeits- und Verlässlichkeitsbewertung von Kommunikationsnetzen und Verteilten Systemen, 5. GI/ITG-Workshop MMBnet 2013, Hamburg, Germany, Sep. 2013. [Pdf] [Bib]