Simone Ferlin

Oslo · Norway

I am a security consultant at IBM since April 2017. I completed my PhD in computer science in 2017 at the Simula Research Lab and Universitetet i Oslo under the supervison of Dr. Ozgu Alay and Prof. Michael Welzl.
My PhD dissertation focused on increasing robustness in multipath transport with MPTCP - here.

In the innovation and research angles on my role, my interests lie in network measurements, performance, security and congestion control. More concrete, I am interested in how the Internet evolves - how technologies are developed, adopted and influence different entities - and how security can be more usable and assessed.

You can find more details about me in my resume and under publications.

I prefer encrypted, signed emails:
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PC member for the ACM SIGCOMM Workshop on Traffic Measurements for Cybersecurity (WTMC) 2018.


Are you interested in BGP analysis and machine learning and looking for a new (paid) challenge? Drop me in an email!


TPC member for the IEEE LCN 2018.


TPC member for the TMA MNM 2018 workshop.


Collaboration with Randy Bush and Cristel Pelsser.


Collaboration with IBM Security Research. Team and blog at: Security Intelligence


TPC member for IEEE IFIP Networking 2018.


Our ToN paper in collaboration with Nokia Bell-Labs entitled "MPTCP meets FEC: Supporting Latency-Sensitive Applications over Heterogeneous Networks" was accepted to be published!


I am temporarily on leave from IBM, interning at IIJ Labs, under supervision of Romain Fontungne and Kenjiro Cho.



MPTCP meets FEC: Supporting Latency-Sensitive Applications over Heterogeneous Networks

IEEE/ACM Transactions on Networking, 2017
Over the past years, TCP has gone through numerous updates to provide performance enhancement under diverse network conditions. However, with respect to losses, little can be achieved with legacy TCP detection and recovery mechanisms. Both fast retransmission and retransmission timeout take at least one extra round trip time to perform, and this might significantly impact performance of latency-sensitive applications, especially in lossy or high delay networks. While forward error correction (FEC) is not a new initiative in this direction, the majority of the approaches consider FEC inside the application. In this paper, we design and implement a framework, where FEC is integrated within TCP. Our main goal with this design choice is to enable latency sensitive applications over TCP in high delay and lossy networks, but remaining application agnostic. We further incorporate this design into multipath TCP (MPTCP), where we focus particularly on heterogeneous settings, considering the fact that TCP recovery mechanisms further escalate head-of-line blocking in multipath. We evaluate the performance of the proposed framework and show that such a framework can bring significant benefits compared to legacy TCP and MPTCP for latency-sensitive real application traffic such as video and web.

TCP with dynamic FEC For High Delay and Lossy Networks

ACM CoNEXT Student Workshop, 2016
TCP has been regularly changed over the past years to address performance enhancement under diverse network conditions. However, its loss recovery mechanisms remain strictly Round Trip Time (RTT) dependent. This makes TCP not suitable especially for networks with high delay and lossy (e.g. satellite networks). This paper proposes to integrate dynamic Forward Error Correction (FEC) in TCP and illustrates the benefits of such framework under various link conditions for different applications.

BLEST: Blocking Estimation-based MPTCP Scheduler for Heterogeneous Networks

IEEE IFIP Networking, 2016
With the widespread availability of multi-homed devices, multipath transport protocols such as MPTCP are becoming increasingly relevant to support better use of multiple connectivity through capacity aggregation and seamless failover. However, capacity aggregation over heterogeneous paths, such as offered by cellular and Wi-Fi networks, is problematic due to the heterogeneity in the underlying network paths. It causes packet reordering leading to head-of-line (HoL) blocking at the receiver, increased end-to-end delays and lower application goodput. MPTCP tackles this issue by penalising the use of longer paths, and increasing buffer sizes. This, however, results in suboptimal resource usage. In this paper, we first evaluate and compare the performance of default MPTCP and alternative state-of-the-art schedulers, all implemented in the Linux kernel, for a range of traffic patterns and network environments. This allows us to identify the shortcomings of the various approaches. We then propose a send-window BLocking ESTimation scheduler, BLEST, to avoid HoL-blocking in heterogeneous networks, thereby increasing the potential for capacity aggregation by reducing the number of spurious retransmissions. The resulting scheduler allows an increase by 15% in application goodput with bulk traffic while reducing unnecessary retransmissions by 80% as compared to default MPTCP and other schedulers.

Revisiting Congestion Control for Multipath TCP with Shared Bottleneck Detection

IEEE Infocom, 2016
Multipath TCP (MPTCP) enables the simultaneous usage of multiple links for bandwidth aggregation, better resource utilization and improved reliability. Its coupled congestion control intends to reap the increased bandwidth of multiple links, while avoiding to be more aggressive than regular TCP flows on every used link.We argue that this leads to a very conservative behavior when paths do not share a bottleneck. Therefore, in this paper, we first quantify the penalty of the coupled congestion control for the links that do not share a bottleneck. Then, in order to overcome this penalty, we design and implement a practical shared bottleneck detection (SBD) algorithm for MPTCP, namely MPTCP-SBD. Through extensive emulations, we show that MPTCP-SBD outperforms all currently deployed MPTCP coupled congestion controls by accurately detecting bottlenecks resulting in throughput gains of up to 30% in the absence of shared bottlenecks while remaining fair to TCP in shared bottlenecks scenarios. We complement the emulation results with real-network experiments justifying it is safeness for deployment.

LISA: A Linked Slow-Start Algorithm for MPTCP

IEEE ICC, 2016
One of the main goals of multipath TCP (MPTCP) is to achieve higher throughput than regular TCP by utilizing multiple paths simultaneously. When these paths share a common bottleneck, MPTCP tries not to be more aggressive than a regular TCP flow. This is achieved by MPTCP's coupled congestion control mechanism that couples the increase factor of MPTCP's subflows in congestion avoidance. However, slow-start remains unchanged and behaves uncoupled for each subflow, affecting MPTCP and concurrent traffic at the bottleneck. We propose LISA, a simple algorithm for coupling MPTCP subflows in slow-start, and investigate the trade-off that this coupling entails. Our evaluations show that coupling in slow-start not only provides gains for MPTCP but also for a concurrent TCP at the bottleneck.

MPTCP Experiences in the NorNet Testbed

IETF MPTCP Working Group
This document collects some experiences of Multi-Path TCP (MPTCP) evaluations in the NorNet testbed.

An Early Look at Multipath TCP Deployment in the Wild

ACM HotPlanet, 2015
Multipath TCP was standardised in 2013 at IETF. It promises better use of network resources of multi-homed devices for capacity aggregation or seamless fail-over capabilities. The uptake has however been rather slow. Some operating systems support MPTCP out of the box, but little is known about their deployment on the server side. We built a scanning infrastructure to search for MPTCP-capable hosts on the Internet. In this study, we used the hosts on the Alexa Top 1M list to test the platform and gain insights into server support. We find that less than 0.1% of the hosts on the Alexa list currently support MPTCP.

Leveraging the IPv4/IPv6 Identity Duality by using Multi-Path Transport

IEEE Global Internet Symposium, 2015
With the 20th anniversary of IPv6 nearing quickly, a growing number of Internet service providers (ISPs) now offer their customers both IPv6 and IPv4 connectivity. This makes multi-homing with IPv4 and IPv6 increasingly common even with just a single ISP connection. Furthermore, the growing popularity of multi-path transport, especially Multi-Path TCP (MPTCP) that is the extension of the well-known Transmission Control Protocol (TCP), leads to the question of whether this identity duality can be utilized for improving application performance in addition to providing resilience. In this paper, we first investigate the ASlevel congruency of IPv4 and IPv6 paths in the Internet. We find that more than 60% of the current IPv4 and IPv6 AS-paths are non-congruent at the AS-level, which motivates us to explore how MPTCP can utilize the IPv4/IPv6 identity duality to improve data transfer performance.

Experimental Evaluation of Multipath TCP Schedulers

ACM Capacity Sharing Workshop, 2014
Today many end hosts are equipped with multiple interfaces. These interfaces can be utilized simultaneously by multipath protocols to pool resources of the links in an efficient way while also providing resilience to eventual link failures. However how to schedule the data segments over multiple links is a challenging problem, and highly influences the performance of multipath protocols. In this paper, we focus on different schedulers for Multipath TCP. We first design and implement a generic modular scheduler framework that enables testing of different schedulers for Multipath TCP. We then use this framework to do an in-depth analysis of different schedulers by running emulated and real-world experiments on a testbed.

Shared Bottleneck Detection for Coupled Congestion Control for RTP Media

IETF RTP Media Congestion Avoidance Techniques
This document describes a mechanism to detect whether end-to-end data flows share a common bottleneck. It relies on summary statistics that are calculated by a data receiver based on continuous measurements and regularly fed to a grouping algorithm that runs wherever the knowledge is needed.

Multi-Path Transport Over Heterogeneous Wireless Networks: Does It Really Pay Off?

IEEE Globecom, 2014
Multi-path transfer protocols such as Concurrent Multi-Path Transfer for SCTP and Multi-Path TCP (MPTCP), are becoming increasingly popular, due to widespread deployment of smartphones with multi-homing support. Although the idea of using multiple interfaces simultaneously to improve application throughput is tempting, does transmission over multiple interfaces always provide benefits especially in realistic setup? In this paper, we first show that multi-path transfer might actually have a negative impact in real-world scenarios with mobile broadband and wireless LAN networks. We then introduce our Dynamic Relative Path Scoring (DRePaS) algorithm that continuously evaluates the contribution of paths to the overall performance and dynamically influences the scheduling decisions to make best use of the paths for the overall system performance.

Practical Passive Shared Bottleneck Detection Using Shape Summary Statistics

IEEE LCN, 2014
Practical shared bottleneck detection has proved to be a difficult problem. We present a novel passive approach using efficient estimates of time and frequency domain summary statistics. The approach is not CPU nor network intensive, and has numerous potential applications in the Internet. Simulations and tests over the Internet and 3G cellular network show its efficacy in grouping flows correctly.

Tackling the Challenge of Bufferbloat in Multi-Path Transport Over Heterogeneous Wireless Networks

IEEE IWQoS, 2014
Today, most of the smart phones are equipped with two network interfaces: Mobile Broadband (MBB) and Wireless Local Area Network (WLAN). Multi-path transport protocols provide increased throughput or reliability, by utilizing these interfaces simultaneously. However, multi-path transmission over networks with very different QoS characteristics is a challenging problem. In this paper, we studied Multi-Path TCP (MPTCP) in heterogeneous networks, specifically MBB networks and WLAN. We first investigate the effect of bufferbloat in MBB on MPTCP performance. We then propose a bufferbloat mitigation algorithm: Multi-Path Transport Bufferbloat Mitigation (MPTBM).

Preempting State Promotions to Improve Application Performance in Mobile Broadband Networks

ACM MobiArch, 2013
Mobile broadband is one of the most common ways of connecting to the Internet. A mobile broadband network is stateful, and a device is allocated different radio resources depending on the state. State promotions take between one and two seconds, and the promotions, or just being in the “wrong” state, can have a severe effect on user experience. Existing work has mostly focused on optimising state changes in order to reduce resource usage in the network, as well as battery consumption on devices. In this paper, we look at how explicitly requesting state promotions can be used to improve application performance.


I was lucky to have met wonderful collaborators that taught me so much about humility and greatness of mind and heart.

Talk Bio

Simone Ferlin is a telecom engineer and has a PhD from the Simula Research Lab and University of Oslo, Norway.
Her interests are primarily in computer networks - wired and wireless. She contributes to transport protocols and congestion control, multipath transport, network performance and security assessment and data analysis. Her past research also includes signal processing for wireless communication systems. Her dissertation focuses on improving robustness in multipath transport. Although the multipath promises are great, increasing both throughput and resilience, it comes with challenges when the underlying network paths are heterogeneous -- challenges which Simone's dissertation addressed working with Multipath TCP (MPTCP).
Simone received her Dipl.-Ing. in Information Technology from Friedrich-Alexander Universitaet Erlangen-Nuernberg, Germany in 2010 and her PhD in Computer Science from the University of Oslo in 2017. She worked in in the NorNet project, which is a real-world large-scale multi-homing testbed for experimental research. She is also very interested in biodiversity conservation and ways to integrate technology into environmental monitoring.


Keywords to my current work & research:

  • IT security - application and transport layer security, automation and continuous monitoring.
  • Multi-path transmission and multipath transport protocols.
  • Network and transport protocol performance measurements.
  • Network programming - Linux, FreeBSD, kernel and user space.
  • Mobile broadband networks - 2 to 4G.
  • Cross-layer design and optimisation.
  • Congestion control.

Current and Past Projects:


  • I enjoy singing (choir) and (try to) play music instruments: Piano, acoustic guitar, and ukulele.
  • I bike. I proudly ride a Gazelle and I am very interested in recumbent bikes. I own an HP Spirit.
  • I am a certified scuba diver. Once upon a time I did triathlon. I hold a blue belt in karate wado-ryu.
  • I read about History of science, and about science and political development in Latin America.
  • I am engaged in biodiversity conservation and environmental politics and I volunteer for Social Coder.