Michael Welzl

• Welzl, Michael; Ott, Jörg; Perkins, Colin; Islam, Safiqul & Kutscher, Dirk (2023). How not to IETF: Lessons Learned From Failed Standardization Attempts, 2023 IEEE International Conference on Pervasive Computing and Communications Workshops and other Affiliated Events (PerCom Workshops). IEEE (Institute of Electrical and Electronics Engineers). ISSN 978-1-6654-5381-3. doi: 10.1109/PerComWorkshops56833.2023.10150250. Full text in Research Archive
• Teymoori, Peyman; Welzl, Michael & Hayes, David Andrew (2023). LGCC: A Novel High-Throughput and Low Delay Paradigm Shift in Multi-Hop Congestion Control. IEEE/ACM Transactions on Networking. ISSN 1063-6692. 32(1), p. 761–776. doi: 10.1109/TNET.2023.3301291. Full text in Research Archive Show summary

  Technological advancements have provided wireless links with very high data rate capacity for 5G/6G mobile networks and WiFi 6, which will be widely deployed by 2025. However, the capacity can have substantial fluctuations, violating the assumption at the transport layer that the capacity is (almost) steady. In this paper, we present a general and efficient, yet deployable solution to this problem through a novel design empowered with a rich theory, allowing a significantly improved experience in using new technologies, especially mobile cellular services. We employ the well-known theory of food-chain models in biology, where a bottleneck link can be modeled as prey, while flows are predators. We extend this model to a chain of predators and preys to form a multi-hop congestion controller, called LGCC. Through simulation evaluation with real-life 5G traces we show the effectiveness of LGCC, compared with the state-of-the-art ABC (Accel-Brake Control). Our results show an order of magnitude bottleneck queuing delay decrease, with only a small decrease in throughput because LGCC tries to never exceed link capacities. LGCC’s design can additionally open a new paradigm in stable multi-hop congestion control and flow aggregation.

• Ciko, Kristjon; Welzl, Michael & Teymoori, Peyman (2023). Going Dark: A Software "Light Switch" for Internet Servers. IEEE Workshop on Local and Metropolitan Area Networks. ISSN 1944-0367. doi: 10.1109/LANMAN58293.2023.10189419. Full text in Research Archive Show summary

  To fight global warming, carbon emissions must urgently be reduced. In this paper, we look at opportunities to do so by diminishing the operational energy usage of an important always-on element of the Internet: server systems. Our measurements from a server host indicate that there is probably not much to be gained by making a significant software change - but, depending on the system, a simple, easily overlooked configuration update may make a difference at no performance cost. This difference is small per server (in the order of an LED light bulb). Given the multitude of permanently operational servers in the world, it may however be significant at scale.

• Welzl, Michael (2022). Not a Trade-Off: On the Wi-Fi Energy Efficiency of Effective Internet Congestion Control, 2022 17th Wireless On-Demand Network Systems and Services Conference (WONS). IEEE (Institute of Electrical and Electronics Engineers). ISSN 978-3-903176-46-1. doi: https:/doi.org/10.23919/WONS54113.2022.9764413.
• Islam, Safiqul; Hiorth, Kristian Andreas; Griwodz, Carsten & Welzl, Michael (2022). Is it really necessary to go beyond a fairness metric for next-generation congestion control? ANRW '22: Proceedings of the Workshop on Applied Networking Research. Association for Computing Machinery (ACM). ISSN 978-1-4503-9444-4. p. 1–7. doi: 10.1145/3547115.3547192. Show summary

  A recent article suggests that the potential for deployment of congestion control mechanisms in the future Internet should be evaluated using a new concept called “harm” instead of measuring “fairness”. While there are good arguments in favor of this new approach, its practical benefits have not yet been experimentally evaluated, and calculating harm requires producing more experimental data. We apply the harm concept to data produced in real-life experiments with competing pairs of various TCP variants: Cubic vs. Reno, BBR vs. Cubic, and Reno vs. Vegas. These experiments cover various levels of “aggression” as well as different feedback types that the controls are based upon. We present a new linear representation of relative harm between scenarios, which can help us to assess the differences in harm between a variety of situations. Among other results, we can see that BBR is on average 1.6 times more harmful to Cubic in high- BDP situations (when Cubic is most aggressive) than Cubic is to Reno.

• Yuan, Gina; Zhang, David; Sotoudeh, Matthew; Welzl, Michael & Winstein, Keith (2022). Sidecar: In-Network Performance Enhancements in the Age of Paranoid Transport Protocols, HotNets '22: Proceedings of the 21st ACM Workshop on Hot Topics in Networks. Association for Computing Machinery (ACM). ISSN 978-1-4503-9899-2. p. 221–227. doi: https:/doi.org/10.1145/3563766.3564113.
• Ciko, Kristjon; Teymoori, Peyman & Welzl, Michael (2022). LGC-ShQ: Datacenter Congestion Control with Queueless Load-Based ECN Marking. Computer communication review. ISSN 0146-4833. 52(4), p. 2–11. doi: 10.1145/3577929.3577931. Show summary

  We present LGC-ShQ, a new ECN-based congestion control mechanism for datacenters. LGC-ShQ relies on ECN feedback from a Shadow Queue, and it uses ECN not only to decrease the rate, but it also increases the rate in relation to this signal. Real-life tests in a Linux testbed show that LGC-ShQ keeps the real queue at low levels while achieving good link utilization and fairness.

• Welzl, Michael; Teymoori, Peyman; Islam, Md Safiqul; Hutchison, David & Gjessing, Stein (2022). Future Internet Congestion Control: The Diminishing Feedback Problem. IEEE Communications Magazine. ISSN 0163-6804. 60(9), p. 87–92. doi: 10.1109/MCOM.006.2200008. Show summary

  It is increasingly difficult for Internet congestion control mechanisms to obtain the feedback that they need. This lack of feedback can have severe performance implications, and it is bound to become worse. In the long run, the problem may only be fixable by fundamentally changing the way congestion control is done in the Internet. We substantiate this claim by looking at the evolution of the Internet's infrastructure over the past 30 years, and by examining the most common behavior of Internet traffic. Considering the goals that congestion control mechanisms are intended to address, and taking into account contextual developments in the Internet ecosystem, we arrive at conclusions and recommendations about possible future congestion control design directions. In particular, we argue that congestion control mechanisms should move away from their strict “end-to-end” adherence. This change would benefit from avoiding a “one size fits all circumstances” approach, and moving toward a more selective set of mechanisms that will result in a better performing Internet. We also discuss how this future vision differs from today's use of performance enhancing proxies.

• Islam, Md Safiqul; Welzl, Michael & Fladby, Tobias (2022). Real-Life Implementation and Evaluation of Coupled Congestion Control for WebRTC Media and Data Flows. IEEE Access. ISSN 2169-3536. 10, p. 95046–95066. doi: 10.1109/ACCESS.2022.3206041. Show summary

  WebRTC enables users to simultaneously transfer media (over the Real-Time Transport Protocol (RTP)) and data (over the Stream Control Transmission Protocol (SCTP)) between web browsers, multiplexed onto a single UDP port pair. This design choice of using two different transport protocols, each with their own congestion control mechanism, can lead to competition between the flows, resulting in undesirable spikes in queuing delay and packet loss. In this paper, we investigate solutions to the harmful effects WebRTC flows cause on each other by having the different congestion controllers of the flows collaborate. Using implementations in the Chromium browser, we show that our mechanism can combine a set of heterogeneous congestion control mechanisms, fairly allocate the available bandwidth between the flows, and reduce overall delay and losses.

• Welzl, Michael; Islam, Safiqul; Gundersen, Michael & Fischer, Andreas (2021). Transport Services: A Modern API for an Adaptive Internet Transport Layer. IEEE Communications Magazine. ISSN 0163-6804. 59(4), p. 16–2242. doi: 10.1109/MCOM.001.2000870. Full text in Research Archive
• Teymoori, Peyman; Hayes, David Andrew; Welzl, Michael & Gjessing, Stein (2021). Estimating an Additive Path Cost With Explicit Congestion Notification. IEEE Transactions on Control of Network Systems. ISSN 2325-5870. 8(2), p. 859–871. doi: 10.1109/TCNS.2021.3053179. Full text in Research Archive
• Ciko, Kristjon; Welzl, Michael & Teymoori, Peyman (2021). PEP-DNA: A Performance Enhancing Proxy for Deploying Network Architectures. In Gunes, Mehmet & Lee, Patrick P.C. (Ed.), 2021 IEEE 29th International Conference on Network Protocols (ICNP 2021). IEEE (Institute of Electrical and Electronics Engineers). ISSN 978-1-6654-4131-5. doi: 10.1109/ICNP52444.2021.9651953.
• Barik, Runa; Welzl, Michael; Fairhurst, Gorry; Elmokashfi, Ahmed; Dreibholz, Thomas & Gjessing, Stein (2020). On the Usability of Transport Protocols other than TCP: A Home Gateway and Internet Path Traversal Study. Computer Networks. ISSN 1389-1286. 173. doi: 10.1016/j.comnet.2020.107211. Full text in Research Archive
• Hayes, David Andrew; Welzl, Michael; Ferlin, Simone; Ros, David & Islam, Safiqul (2020). Online Identification of Groups of Flows Sharing a Network Bottleneck. IEEE/ACM Transactions on Networking. ISSN 1063-6692. 28(5), p. 2229–2242. doi: 10.1109/TNET.2020.3007346. Full text in Research Archive
• Welzl, Michael; Teymoori, Peyman; Gjessing, Stein & Islam, Safiqul (2020). Follow the Model: How Recursive Networking Can Solve the Internet's Congestion Control Problems, 2020 International Conference on Computing, Networking and Communications (ICNC) . IEEE conference proceedings. ISSN 978-1-7281-4905-9. p. 518–524. doi: 10.1109/ICNC47757.2020.9049648. Full text in Research Archive
• Barik, Runa; Welzl, Michael; Teymoori, Peyman; Islam, Safiqul & Gjessing, Stein (2020). Performance Evaluation of In-network Packet Retransmissions using Markov Chains, 2020 International Conference on Computing, Networking and Communications (ICNC) . IEEE conference proceedings. ISSN 978-1-7281-4905-9. Full text in Research Archive
• Ciko, Kristjon; Welzl, Michael & Marek, Marcel (2020). TAPS and RINA: Do they fit together? In Chatras, Bruno & Lopez, Diego (Ed.), 2020 23rd Conference on Innovation in Clouds, Internet and Networks and Workshops (ICIN). IEEE (Institute of Electrical and Electronics Engineers). ISSN 978-1-7281-5127-4. p. 35–40. doi: 10.1109/ICIN48450.2020.9059406.
• Marek, Marcel; Teymoori, Peyman; Gjessing, Stein & Welzl, Michael (2019). High-Rate Data Transfer with Congestion-Aware Multipath Routing. In Unknown, Person (Eds.), IEEE GLOBECOM 2019 Workshops. IEEE (Institute of Electrical and Electronics Engineers). ISSN 978-1-7281-0961-9. doi: 10.1109/GCWkshps45667.2019.9024564.
• Islam, Safiqul; Welzl, Michael & Gjessing, Stein (2019). How to Control a TCP: Minimally-Invasive Congestion Management for Datacenters. In Ansari, Nirwan & Wang, Honggang (Ed.), Proceedings of the 2019 International Conference on Computing, Networking and Communications (ICNC): Green Computing, Networking, and Communications. IEEE Sarnoff Symposium. ISSN 978-1-5386-9223-3. p. 121–125. doi: 10.1109/ICCNC.2019.8685516. Full text in Research Archive
• Welzl, Michael; Islam, Safiqul; Barik, Runa; Gjessing, Stein & Elmokashfi, Ahmed Mustafa Abdalla (2019). Investigating the Delay Impact of the DiffServ Code Point (DSCP). In Ansari, Nirwan & Wang, Honggang (Ed.), Proceedings of the 2019 International Conference on Computing, Networking and Communications (ICNC): Green Computing, Networking, and Communications. IEEE Sarnoff Symposium. ISSN 978-1-5386-9223-3. p. 612–616. doi: 10.1109/ICCNC.2019.8685538. Full text in Research Archive
• Ciko, Kristjon & Welzl, Michael (2019). First Contact: Can Switching to RINA save the Internet? In Galis, Alex; Guillemin, Fabrice; Noldus, Rogier; Secci, Stefano; Filip, Idzikowski & Sayit, Müge Fesci (Ed.), 22nd Conference on Innovation in Clouds, Internet and Networks and Workshops, ICIN 2019. IEEE (Institute of Electrical and Electronics Engineers). ISSN 978-1-5386-8336-1. p. 37–42. doi: 10.1109/ICIN.2019.8685912.
• Hiorth, Kristian Andreas & Welzl, Michael (2019). Design Considerations for RINA Congestion Control over WiFi Links. In Galis, Alex; Guillemin, Fabrice; Noldus, Rogier; Secci, Stefano; Idzikowski, Filip & Sayit, Müge Fesci (Ed.), 2019 22nd Conference on Innovation in Clouds, Internet and Networks and Workshops (ICIN). IEEE (Institute of Electrical and Electronics Engineers). ISSN 978-1-5386-8336-1. p. 54–59. doi: 10.1109/ICIN.2019.8685874.
• Barik, Runa; Welzl, Michael; Elmokashfi, Ahmed; Dreibholz, Thomas; Islam, Safiqul & Gjessing, Stein (2019). On the Utility of Unregulated IP DiffServ Code Point (DSCP) Usage by End Systems. Performance evaluation (Print). ISSN 0166-5316. 135. doi: 10.1016/j.peva.2019.102036. Full text in Research Archive
• Bianchi, Giuseppe; Welzl, Michael; Tulumello, Angelo; Gringoli, Francesco; Belocchi, Giacomo & Faltelli, Marco [Show all 7 contributors for this article] (2019). XTRA: Towards portable transport layer functions. IEEE Transactions on Network and Service Management. ISSN 1932-4537. 16(4), p. 1507–1521. doi: 10.1109/TNSM.2019.2948467. Full text in Research Archive
• Ijaz, Humaira; Jameel, Bushra & Welzl, Michael (2019). A survey and comparison on overlay‐underlay mapping techniques in peer‐to‐peer overlay networks. International Journal of Communication Systems. ISSN 1074-5351. 32(3), p. 1–26. doi: 10.1002/dac.3872. Full text in Research Archive
• Pontarelli, Salvatore; Bianchi, Giuseppe & Welzl, Michael (2019). A Programmable Hardware Calendar for High Resolution Pacing, IEEE International Conference on High Performance Switching and Routing (HPSR) 2018. IEEE Sarnoff Symposium. ISSN 978-1-5386-5541-2. p. 1–6. doi: 10.1109/HPSR.2018.8850731. Full text in Research Archive
• Barik, Runa; Welzl, Michael; Elmokashfi, Ahmed Mustafa Abdalla; Dreibholz, Thomas & Gjessing, Stein (2018). Can WebRTC QoS Work? A DSCP Measurement Study. In Reichl, Peter; Hossfeld, Tobias; Guiseppe, Bianchi; Zinner, Tobias & Altman, Eitan (Ed.), ITC 30 - Teletraffic in a Smart World. IEEE Press. ISSN 978-0-9883045-5-0. p. 167–175. doi: https:/doi.org/10.1109/ITC30.2018.00034.
• Bianchi, Giuseppe; Welzl, Michael; Tulumello, Angelo; Belocchi, Belocci; Faltelli, Marco & Pontarelli, Salvatore (2018). A fully portable TCP implementation using XFSMs, Proceedings of ACM SIGCOMM 2018 Conference on Posters and Demos. Association for Computing Machinery (ACM). ISSN 978-1-4503-5915-3. p. 99–101. doi: 10.1145/3234200.3234237.
• Islam, Safiqul; Welzl, Michael & Gjessing, Stein (2018). Lightweight and flexible single-path congestion control coupling, NOMS 2018 - 2018 IEEE/IFIP Network Operations and Management Symposium. IEEE Sarnoff Symposium. ISSN 978-1-5386-3416-5. p. 1–6. doi: 10.1109/NOMS.2018.8406137. Full text in Research Archive
• Islam, Safiqul; Welzl, Michael; Hiorth, Kristian Andreas; Hayes, David; Armitage, Grenville & Gjessing, Stein (2018). ctrlTCP: Reducing latency through coupled, heterogeneous multi-flow TCP congestion control, IEEE INFOCOM 2018 - IEEE Conference on Computer Communications Workshops (INFOCOM WKSHPS). IEEE Sarnoff Symposium. ISSN 978-1-5386-5979-3. p. 214–219. doi: 10.1109/INFCOMW.2018.8406887. Full text in Research Archive
• Marek, Marcel; Teymoori, Peyman; Welzl, Michael & Gjessing, Stein (2018). Computer-Aided Reproducibility. In IEEE, . (Eds.), Proceedings of International Conference on Computing, Networking and Communications (ICNC 2018). IEEE conference proceedings. ISSN 1111111111. p. 127–133. doi: 10.1109/ICCNC.2018.8390274. Full text in Research Archive
• Barik, Runa; Welzl, Michael; Elmokashfi, Ahmed Mustafa Abdalla; Gjessing, Stein & Islam, Safiqul (2017). fling: A Flexible Ping for Middlebox Measurements. In Davoli, Franco & Jain, Nikhil (Ed.), Teletraffic Congress (ITC 29), 2017 29th International. IEEE Sarnoff Symposium. ISSN 978-0-9883045-3-6. p. 134–142. doi: 10.23919/ITC.2017.8064349. Full text in Research Archive
• Barik, Runa; Divakaran, Dinil Mon & Welzl, Michael (2017). Characterizing the Effects of TCP's Initial Window. In Vuran, Mehmet Can & Xie, Linda Jiang (Ed.), 2017 IEEE Conference on Computer Communications Workshops (INFOCOM WKSHPS) . IEEE Sarnoff Symposium. ISSN 978-1-5386-2784-6. p. 886–891. doi: https:/doi.org/10.1109/INFCOMW.2017.8116493.
• Khademi, Naeem; Welzl, Michael; Armitage, Grenville; Ros, David; Zander, Sebastian & Fairhurst, Gorry (2017). Alternative Backoff: Achieving Low Latency and High Throughput with ECN and AQM, 16th International IFIP TC6 Networking Conference, Networking 2017. IFIP Open Digital Library. ISSN 978-3-901882-94-4. doi: 10.23919/ifipnetworking.2017.8264863. Show summary

  A number of recently proposed Active Queue Management (AQM) mechanisms instantiate shallow buffers with burst tolerance to minimise the time that packets spend enqueued at a bottleneck. However, shallow buffering causes noticeable TCP performance degradation as a path’s underlying round trip time (RTT) heads above typical intra-country levels. Using less-aggressive multiplicative backoffs in TCP can compensate for shallow bottleneck buffering. AQM mechanisms may either drop packets or mark them using Explicit Congestion Notification (ECN), depending on whether the sender marked packets as ECN-capable. While a drop may therefore stem from any type of queue, an ECN-mark indicates that an AQM mechanism has done its job, and therefore the queue is likely to be shallow. We propose ABE: "Alternative Backoff with ECN", which consists of enabling ECN and letting individual TCP senders back off less aggressively in reaction to ECN-marks from AQM-enabled bottlenecks. Using controlled testbed experiments with standard NewReno and CUBIC flows, we show significant performance gains in lightly-multiplexed scenarios, without losing the delay-reduction benefits of deploying AQM. ABE is a sender-side-only modification that can be deployed across networks incrementally (requiring no flag-day) and offers a compelling reason to deploy and enable ECN across the Internet.

• Khademi, Naeem; Ros, David; Welzl, Michael; Bozakov, Zdravko; Brunstrom, Anna & Fairhurst, Gorry [Show all 13 contributors for this article] (2017). NEAT: A Platform- and Protocol-Independent Internet Transport API. IEEE Communications Magazine. ISSN 0163-6804. 55(6), p. 46–54. doi: 10.1109/MCOM.2017.1601052. Full text in Research Archive
• Papastergiou, Giorgos; Fairhurst, Gorry; Ros, David; Brunstrom, Anna; Grinnemo, Karl-Johan & Hurtig, Per [Show all 11 contributors for this article] (2017). De-Ossifying the Internet Transport Layer: A Survey and Future Perspectives. IEEE Communications Surveys and Tutorials. ISSN 1553-877X. 19(1), p. 619–639. doi: 10.1109/COMST.2016.2626780. Full text in Research Archive Show summary

  It is widely recognized that the Internet transport layer has become ossified, where further evolution has become hard or even impossible. This is a direct consequence of the ubiquitous deployment of middleboxes that hamper the deployment of new transports, aggravated further by the limited flexibility of the application programming interface (API) typically presented to applications. To tackle this problem, a wide range of solutions have been proposed in the literature, each aiming to address a particular aspect. Yet, no single proposal has emerged that is able to enable evolution of the transport layer. In this paper, after an overview of the main issues and reasons for transport-layer ossification, we survey proposed solutions and discuss their potential and limitations. The survey is divided into five parts, each covering a set of point solutions for a different facet of the problem space: (1) designing middlebox-proof transports; (2) signaling for facilitating middlebox traversal; (3) enhancing the API between the applications and the transport layer; (4) discovering and exploiting end-to-end capabilities; and (5) enabling user-space protocol stacks. Based on this analysis, we then identify further development needs toward an overall solution. We argue that the development of a comprehensive transport layer framework, able to facilitate the integration and cooperation of specialized solutions in an application-independent and flexible way, is a necessary step toward making the Internet transport architecture truly evolvable. To this end, we identify the requirements for such a framework and provide insights for its development.

• Islam, Safiqul; Welzl, Michael; Gjessing, Stein & You, Jianjie (2016). OpenTCP: Combining congestion controls of parallel TCP connections. In Guojian Cheng, Xi'an (Eds.), 2016 IEEE Advanced Information Management, Communicates, Electronic and Automation Control Conference (IMCEC). IEEE (Institute of Electrical and Electronics Engineers). ISSN 978-1-4673-9613-4. p. 194–198. doi: 10.1109/IMCEC.2016.7867199.
• Barik, Runa; Welzl, Michael; Ferlin, Simone & Alay, Ozgu (2016). LISA: A linked slow-start algorithm for MPTCP. In Bregni, Stefano & Fonseca, Nelson (Ed.), IEEE International Conference on Communications (ICC 2016). IEEE Sarnoff Symposium. ISSN 978-1-4799-6664-6. doi: 10.1109/ICC.2016.7510786.
• Barik, Runa; Welzl, Michael & Elmokashfi, Ahmed (2016). How to say that you're special: Can we use bits in the IPv4 header? Proceedings of the 2016 Applied Networking Research Workshop. Association for Computing Machinery (ACM). ISSN 978-1-4503-4443-2. p. 68–70. doi: 10.1145/2959424.2959442. Full text in Research Archive
• Islam, Safiqul & Welzl, Michael (2016). Start Me Up: Determining and Sharing TCP's Initial Congestion Window, Proceedings of the 2016 Applied Networking Research Workshop. Association for Computing Machinery (ACM). ISSN 978-1-4503-4443-2. p. 52–54. doi: 10.1145/2959424.2959440. Full text in Research Archive Show summary

  When multiple TCP connections are used between the same host pair, they often share a common bottleneck – especially when they are encapsulated together, e.g. in VPN scenarios. Then, all connections after the first should not have to guess the right initial value for the congestion window, but rather get the appropriate value from other connections. This allows short flows to complete much faster – but it can also lead to large bursts that cause problems on their own. Prior work used timer-based pacing methods to alleviate this problem; we introduce a new algorithm that “paces” packets by instead correctly maintaining the ACK clock, and show its positive impact in combination with a previously presented congestion coupling algorithm.

• Islam, Safiqul; Welzl, Michael; Hayes, David Andrew & Gjessing, Stein (2016). Managing Real-Time Media Flows through a Flow State Exchange. In Badonnel, Semma (Eds.), Proceedings of NOMS 2016 - 2016 IEEE/IFIP Network Operations and Management Symposium. IEEE conference proceedings. ISSN 978-1-5090-0223-8. p. 112–120. doi: 10.1109/NOMS.2016.7502803.
• Teymoori, Peyman; Welzl, Michael; Gjessing, Stein; Grasa, Eduard; Riggio, Roberto & Rausch, Kewin [Show all 7 contributors for this article] (2016). Congestion control in the recursive InterNetworking Architecture (RINA). In Bregni, Stefano & Fonseca, Nelson (Ed.), IEEE International Conference on Communications (ICC 2016). IEEE Sarnoff Symposium. ISSN 978-1-4799-6664-6. doi: 10.1109/ICC.2016.7510818.
• Teymoori, Peyman; Hayes, David Andrew; Welzl, Michael & Gjessing, Stein (2016). Even Lower Latency, Even Better Fairness: Logistic Growth Congestion Control in Datacenter. In Kanhere, Salil & Mnaouer, Adel Ben (Ed.), Proceedings 2016 IEEE 41st Conference on Local Computer Networks (LCN) 2016. IEEE (Institute of Electrical and Electronics Engineers). ISSN 978-1-5090-2054-6. p. 10–18. doi: 10.1109/LCN.2016.12.
• Welzl, Michael; Gjessing, Stein & Jahre, Håkon Botnmark (2016). Fighting fire with fire: Eliminating standing queues with large UDP packet floods. In Yang, Liuqing (Eds.), Proceedings of International Conference on Computing, Networking and Communications (ICNC), 2016. IEEE conference proceedings. ISSN 978-1-4673-8579-4. p. 656–660. doi: 10.1109/ICCNC.2016.7440667.
• Ferlin, Simone; Alay, Ozgu; Dreibholz, Thomas; Hayes, David Andrew & Welzl, Michael (2016). Revisiting congestion control for multipath TCP with shared bottleneck detection. IEEE Infocom. Proceedings. ISSN 0743-166X. 2016-July. doi: 10.1109/INFOCOM.2016.7524599.
• Hayes, David A.; Teymoori, Peyman & Welzl, Michael (2016). Feedback in recursive congestion control. Lecture Notes in Computer Science (LNCS). ISSN 0302-9743. 9951 LNCS, p. 109–125. doi: 10.1007/978-3-319-46433-6_8.
• Briscoe, Bob; Brunstrom, Anna; Petlund, Andreas; Hayes, David Andrew; Ros, David & Tsang, Ing-Jyh [Show all 10 contributors for this article] (2016). Reducing internet latency: a survey of techniques and their merits. IEEE Communications Surveys and Tutorials. ISSN 1553-877X. 18(3), p. 2149–2196. doi: 10.1109/COMST.2014.2375213.
• Rajiullah, Mohammad; Hurtig, Per; Brunstrom, Anna; Petlund, Andreas & Welzl, Michael (2015). An evaluation of tail loss recovery mechanisms for TCP. Computer communication review. ISSN 0146-4833. 45(1), p. 5–11. doi: 10.1145/2717646.2717648.
• Islam, Safiqul; Welzl, Michael; Gjessing, Stein & Khademi, Naeem (2015). Coupled congestion control for RTP media. Computer communication review. ISSN 0146-4833. 44(4). doi: 10.1145/2630088.2630089.
• Hayes, David Andrew; Ferlin, Simone & Welzl, Michael (2014). Practical passive shared bottleneck detection using shape summary statistics. In Kanhere, Salil & Akkaya, Kernal (Ed.), 39th Annual IEEE Conference on Local Computer Networks (LCN 2014). IEEE (Institute of Electrical and Electronics Engineers). ISSN 978-1-4799-3780-6. p. 150–158. doi: 10.1109/LCN.2014.6925767.
• Elkhatib, Yehia; Tyson, Gareth & Welzl, Michael (2014). Can SPDY Really Make the Web Faster? 2014 IFIP Networking Conference. IEEE conference proceedings. ISSN 978-3-901882-58-6. p. 100–108. doi: 10.1109/IFIPNetworking.2014.6857089.
• Welzl, Michael; Gjessing, Stein & Khademi, Naeem (2014). Less-than-best-effort service for Community Wireless Networks: Challenges at three layers. In Hui, Pan & Karlson, Gunnar (Ed.), 11th Annual Conference on Wireless On-demand Network Systems and Services. IEEE conference proceedings. ISSN 978-1-4799-4937-3. p. 148–153. doi: 10.1109/WONS.2014.6814737.
• Islam, Safiqul; Welzl, Michael; Gjessing, Stein & Khademi, Naeem (2014). Coupled congestion control for RTP media. In Kühlewind, Mirja & Kutscher, Dirk (Ed.), Proceedings of the 2014 ACM SIGCOMM workshop on Capacity sharing workshop. Association for Computing Machinery (ACM). ISSN 978-1-4503-2991-0. p. 21–26. doi: 10.1145/2630088.2630089.
• Yousaf, Muhammad & Welzl, Michael (2014). Network-Aware HEFT Scheduling for Grid. Scientific World Journal. ISSN 1537-744X. 2014. doi: 10.1155/2014/317284.
• Yousaf, Muhammad Murtaza & Welzl, Michael (2013). On the Accurate Identification of Network Paths Having a Common Bottleneck. Scientific World Journal. ISSN 1537-744X. doi: 10.1155/2013/890578.
• Ijaz, Humaira; Saleem, Sadia & Welzl, Michael (2013). Fewest Common Hops (FCH): An Improved Peer Selection Approach for P2P Applications, Parallel, Distributed and Network-Based Processing (PDP), 2013 21st Euromicro International Conference on. IEEE (Institute of Electrical and Electronics Engineers). ISSN 978-0-7695-4939-2. p. 449–453. doi: 10.1109/PDP.2013.73. Full text in Research Archive
• Ros, D. & Welzl, Michael (2013). Assessing LEDBAT's Delay Impact. IEEE Communications Letters. ISSN 1089-7798. 17(5), p. 1044–1047. doi: 10.1109/LCOMM.2013.040213.130137.
• Ros, David & Welzl, Michael (2013). Less-than-Best-Effort Service: A Survey of End-to-End Approaches. IEEE Communications Surveys and Tutorials. ISSN 1553-877X. 15(2), p. 898–908. doi: 10.1109/SURV.2012.060912.00176.
• Welzl, Michael & Normann, Rolf Erik Gurandsrud (2012). A Client-side Split-ACK Tool for TCP Slow Start Investigation, 2012 International Conference on Computing, Networking and Communications (ICNC). IEEE Sarnoff Symposium. ISSN 978-1-4673-0009-4. p. 804–808. doi: 10.1109/iccnc.2012.6167535.
• Khademi, Naeem; Welzl, Michael & Gjessing, Stein (2012). Experimental evaluation of TCP performance in multi-rate 802.11 WLANs. In Banchs, Albert & Prabhakaran, Balakrishnan (Ed.), 2012 IEEE international symposium on a world of wireless, mobile, and multimedia networks, WoWMoM. IEEE conference proceedings. ISSN 978-1-4673-1238-7. p. 1–9. doi: 10.1109/wowmom.2012.6263696. Show summary

  The goal of Rate Adaptation (RA) mechanisms in 802.11 WLANs is to provide optimum system throughput under varying channel conditions (e.g. in presence of noise) by carrying out run-time prediction and selection of the most appropriate bit-rate. The cross-layer interaction of TCP, as the major transport protocol in the Internet, with different RA mechanisms and DCF is yet to be thoroughly investigated. Previously reported efforts A) have never included real-life measurements of uplink TCP traffic; B) lack a practical view because they do not consider the RA mechanisms commonly deployed in today's off-the-shelf 802.11 devices; C) miss the study of RA mechanisms in low-noise environments. This paper covers all the above shortages, by conducting real-life measurements in two different test-beds (NDlab and Emulab) alongside with simulations, to study the performance of TCP coupled with different commonly deployed RA mechanisms. Our measurements reveal that 1) most conventional RA mechanisms are unable to distinguish frame errors due to collisions from channel noise/interference, and will respond to them negatively to some extent; 2) different than downlink TCP, uplink TCP can be adversely affected by collision-triggered rate downshifts that some RA schemes exhibit even under perfect channel conditions or in low-noise environments; 3) the relatively recent Minstrel RA mechanism can counter this negative uplink behavior well, yielding almost equal performance as in the downlink case.

• Munir, Kashif; Lo Cigno, Renato; Primet Vicat-Blanc, Pascale & Welzl, Michael (2012). Planning Data Transfers in Grids: A Multi-Service Queueing Approach. Concurrency and Computation. ISSN 1532-0626. 24(4), p. 407–422. doi: 10.1002/cpe.1742.
• Schier, Michael & Welzl, Michael (2012). Optimizing Selective ARQ for H. 264 Live Streaming: A Novel Method for Predicting Loss-Impact in Real Time. IEEE transactions on multimedia. ISSN 1520-9210. 14(2), p. 415–430. doi: 10.1109/TMM.2011.2178235.
• Munir, Kashif; Welzl, Michael; Pasin, Marcelo & Primet Vicat-Blanc, Pascale (2012). Combining Explicit Admission Control and Congestion Control for Predictable Data Transfers in Grids. Future Generation Computer Systems. ISSN 0167-739X. 28(7), p. 1121–1132. doi: 10.1016/j.future.2011.06.012.
• Welzl, Michael; Abfalterer, Armin & Gjessing, Stein (2011). XCP vs. CUBIC with Quick-Start: Observations on Implicit vs. Explicit Feedback for Congestion Control. IEEE International Conference on Communications. ISSN 1550-3607. doi: 10.1109/icc.2011.5963377.
• Welzl, Michael; Niederbacher, Florian & Gjessing, Stein (2011). Beneficial Transparent Deployment of SCTP: the Missing Pieces. In N., N. (Eds.), 2011 IEEE Global Telecommunications Conference - GLOBECOM 2011. IEEE Sarnoff Symposium. ISSN 978-1-4244-9268-8.
• Schier, Michael & Welzl, Michael (2011). Video Streaming using Content-Aware Unequal Error Protection Fountain Codes. In N, N (Eds.), CCNC 2011: IEEE Consumer Communications and Networking Conference; 9-12 Jan. 2011, Las Vegas. IEEE conference proceedings. ISSN 978-1-4244-8790-5. p. 525–526. doi: 10.1109/ccnc.2011.5766530.
• Schier, Michael & Welzl, Michael (2011). A content-aware rateless error protection scheme for live video streaming systems. In N., N. (Eds.), 2011 IEEE International Symposium on a World of Wireless, Mobile and Multimedia Networks (WoWMoM). IEEE Press. ISSN 978-1-4577-0352-2. doi: 10.1109/wowmom.2011.5986437.
• Hayes, David A.; Welzl, Michael; Armitage, Grenville & Rossi, Mattia (2011). Improving HTTP performance using 'Stateless' TCP. In N., N. (Eds.), Proceedings of the 21st international workshop on Network and operating systems support for digital audio and video. Association for Computing Machinery (ACM). ISSN 978-1-4503-0777-2. p. 57–62. doi: 10.1145/1989240.1989256.
• Khademi, Naeem; Welzl, Michael & Lo Cigno, Renato (2011). On the uplink performance of TCP in multi-rate 802.11 WLANs. In N., N. (Eds.), NETWORKING'11 Proceedings of the 10th international IFIP TC 6 conference on Networking. Springer. ISSN 978-3-642-20797-6. p. 368–378. doi: 10.1007/978-3-642-20798-3_28.
• Stewart, Lawrence; Hayes, David A.; Armitage, Grenville; Welzl, Michael & Petlund, Andreas (2011). Multimedia-unfriendly TCP congestion control and home gateway queue management. In N., N. (Eds.), MMSys '11 Proceedings of the second annual ACM conference on Multimedia systems. Association for Computing Machinery (ACM). ISSN 978-1-4503-0518-1. p. 35–44. doi: 10.1145/1943552.1943558.
• Nguyen, Anh Tuan; Eliassen, Frank & Welzl, Michael (2011). Quality-aware Membership Management for Layered Peer-to-Peer Streaming. In N, N (Eds.), CCNC 2011: IEEE Consumer Communications and Networking Conference; 9-12 Jan. 2011, Las Vegas. IEEE conference proceedings. ISSN 978-1-4244-8790-5. p. 720–724. doi: 10.1109/ccnc.2011.5766585.
• Nguyen, Anh Tuan; Li, Baochun; Welzl, Michael & Eliassen, Frank (2011). Stir: Spontaneous Social Peer-to-Peer Streaming. In Ni, Lionel & Zhang, WenJun (Ed.), 2011 IEEE Conference on Computer Communications Workshops (INFOCOM WKSHPS). IEEE Sarnoff Symposium. ISSN 978-1-4577-0248-8. p. 816–821. doi: 10.1109/infcomw.2011.5928925.
• Welzl, Michael; Jörer, Stefan & Gjessing, Stein (2011). Towards a Protocol-Independent Internet Transport API. In Uji, Noritaka (Eds.), 2011 IEEE International Conference on Communications Workshops (ICC). IEEE Sarnoff Symposium. ISSN 978-1-61284-955-3. doi: 10.1109/iccw.2011.5963568.
• Welzl, Michael; Abfalterer, Armin & Gjessing, Stein (2011). XCP vs. CUBIC with Quick-Start: Observations on Implicit vs. Explicit Feedback for Congestion Control. In Uji, Noritaka (Eds.), 2011 IEEE International Conference on Communications (ICC). IEEE Sarnoff Symposium. ISSN 978-1-61284-233-2. doi: 10.1109/icc.2011.5963377.
• Damjanovic, Dragana & Welzl, Michael (2011). An Extension of the TCP Steady-State Throughput Equation for Parallel Flows and its Application in MulTFRC. IEEE/ACM Transactions on Networking. ISSN 1063-6692. 19(6), p. 1676–1689. doi: 10.1109/TNET.2011.2142008.
• Welzl, Michael; Niederbacher, Florian & Gjessing, Stein (2011). Beneficial Transparent Deployment of SCTP: the Missing Pieces. GLOBECOM - conference record / IEEE Global Telecommunications Conference. ISSN 0895-1195.
• Schier, Michael & Welzl, Michael (2010). Content-Aware Selective Reliability for DCCP Video Streaming. In Falah, Abdul Aziz (Eds.), Multimedia Computing and Information Technology (MCIT), 2010 International Conference On. IEEE Sarnoff Symposium. ISSN 978-1-4244-7003-7. p. 53–56.

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• Welzl, Michael; Karlsson, Gunnar; Alay, Ozgu & Peng, Chunyi (2022). 2022 17th Wireless On-Demand Network Systems and Services Conference (WONS). IEEE (Institute of Electrical and Electronics Engineers). ISBN 978-3-903176-46-1. 150 p.

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• Welzl, Michael; Oepen, Stephan; Cezary Jaskula, Cezary; Griwodz, Carsten & Islam, Safiqul (2021). Collaboration in the IETF: an initial analysis of two decades in email discussions. Computer communication review. ISSN 0146-4833. 51(3), p. 29–32. doi: 10.1145/3477482.3477488. Show summary

  RFC 9000, published in May 2021, marks an important milestone for the Internet's standardization body, the Internet Engineering Task Force (IETF): finally, the specification of the QUIC protocol is available. QUIC is the result of a five-year effort - and it is also the second of two major protocols (the first being SPDY, which later became HTTP/2) that Google LLC first deployed, and then brought to the IETF for standardization. This begs the question: when big players follow such a "shoot first, discuss later" approach, is IETF collaboration still "real", or is the IETF now being (mis-)used to approve protocols for standardization when they are already practically established, without really actively involving anyone but the main proponents?

• Khademi, Naeem; Welzl, Michael; Armitage, Grenville & Gjessing, Stein (2016). Improving the Fairness of Alternative Backoff with ECN (ABE). Show summary

  Abstract: Explicit Congestion Notification (ECN) lets a bottleneck's Active Queue Management (AQM) mechanism inform an endpoint about congestion without having to drop a packet. A recently proposed sender-side modification called Alternative Backoff with ECN (ABE) enables reduced latency while maintaining good utilization with ECN. However, under certain circumstances ABE can produce a degree of unfair behavior between ABE-enabled TCP senders and conventional TCP senders. We propose specific guidance for configuring bottleneck AQMs to assist in fairness between ABE-enabled and conventional TCP flows. We evaluate our proposal using RED, then describe how it can be applied to other AQM mechanisms and incrementally introduced into the Internet.

• Islam, Safiqul; Welzl, Michael & Gjessing, Stein (2013). One Control to Rule Them All - Coupled Congestion Control for RTP Media.
• Ciko, Kristjon; Welzl, Michael & Teymoori, Peyman (2022). Improving Internet Performance with a "Clean-Slate" Network Architecture - The Case of RINA. Universitetet i Oslo. ISSN 1501-7710. Full text in Research Archive Show summary

  Today’s Internet is facing significant challenges as the number of the connected devices, applications, and the amount of traffic grow tremendously. The challenges are particularly related to the insufficient security and performance, complexity in providing mobility and multihoming, and the inability to easily accommodate new protocols and technologies. Over the last two decades, there has been considerable effort by the networking research community to evolve or redesign the Internet architecture. Unlike evolutionary approaches, “clean-slate” designs follow a more drastic path to overcome the fundamental architecture limitations of the current Internet. However, such solutions are facing large deployment barriers, mainly because the Internet does not provide architectural modularity. Among the “clean-slate” initiatives, RINA—the Recursive InterNetwork Architecture—is perhaps the most drastic one which attempts to offer a general solution with a complete networking theory. In addition, the recursive nature of RINA introduces potential benefits in many aspects of networking such as management, routing, security, and congestion control. This dissertation tackles the deployment challenges and investigates several strategies to deploy a new clean-slate architecture such as RINA in the current networks. These strategies are: (1) direct usage with a fall-back, (2) adapting the Application Programming Interface (API), and (3) a gateway to translate between protocols. Real-life experiments of the first congestion control approach that is suitable for a flexible recursive architecture show the performance improvement that can be attained with these strategies.

• Ciko, Kristjon; Welzl, Michael & Teymoori, Peyman (2021). PEP-DNA: a Performance Enhancing Proxy for Deploying Network Architectures. Universitetet i Oslo. ISSN 978-82-7368-600-8. Full text in Research Archive Show summary

  Deploying a new network architecture in the Internet requires changing some, but not necessarily all elements between communicating applications. One way to achieve gradual deployment is a proxy or gateway which “translates” between the new architecture and TCP/IP. We present such a proxy, called “Performance Enhancing Proxy for Deploying Network Architectures (PEP-DNA)”, which allows TCP/IP applications to benefit from advanced features of a new network architecture without having to be redeveloped. Our proxy is a kernel-based Linux implementation which can be installed wherever a translation needs to occur between a new architecture and TCP/IP domains. We discuss the proxy operation in detail and evaluate its efficiency and performance in a local testbed, demonstrating that it achieves high throughput with low additional latency and low CPU and memory overhead. In our experiments we use the Recursive InterNetwork Architecture (RINA) and Information- Centric Networking (ICN) as examples, but our proxy is modular and flexible, and hence enables realistic gradual deployment of any new “clean-slate” approaches.

• Teymoori, Peyman & Welzl, Michael (2020). LGCC: Food Chain Multi-Hop Congestion Control. University of Oslo. ISSN 978-82-7368-459-2. Full text in Research Archive
• Teymoori, Peyman; Hayes, David Andrew; Welzl, Michael & Gjessing, Stein (2019). Estimating an Additive Path Cost with Explicit Congestion Notification. Universitetet i Oslo. ISSN 978-82-7368-452-3. Full text in Research Archive
• Li, Qian & Welzl, Michael (2017). Vulture – Variable Aggressiveness Ultra Low Impact Transport Using Receiver-based Flow-control Mechanism. 7Letras. ISSN 978-82-7368-439-4. Full text in Research Archive
• Islam, Safiqul; Welzl, Michael; Gjessing, Stein & Khademi, Naeem (2014). Coupled Congestion Control for RTP Media. University of Oslo. ISSN 978-82-7368-405-9. Full text in Research Archive Show summary

  Congestion occurs at a bottleneck along an Internet path; multiple flows between the same sender and receiver pairs can benefit from using only a single congestion control instance when they share the same bottleneck. These benefits include the ability to control the rate allocation between flows and reduced overall delay (multiple congestion control instances cause more queuing delay than one since each has no knowledge of the congestion episodes experienced by the others). We present a mechanism for coupling congestion control for real-time media and show its benefits by coupling multiple congestion controlled flows that share the same bottleneck.

• Khademi, Naeem; Ros, David & Welzl, Michael (2013). The New AQM Kids on the Block: Much Ado About Nothing? Universitetet i Oslo. ISSN 82-7368-399-0. Full text in Research Archive Show summary

  Active Queue Management (AQM) design has again come into the spotlight of network operators, vendors and OS developers. This reflects the growing concern and sensitivity about the end-to-end latency perceived by today’s Internet users. Indeed, delays on the order of seconds have become common due to the deployment of excessively-sized FIFO/DropTail buffers at the edge of many networks. CoDel and PIE are two AQM mechanisms that have recently been presented and discussed at the IRTF and the IETF. However, to the best of our knowledge, they have not yet been thoroughly evaluated or compared against each other except by simulation. We set thus to perform an experimental evaluation using real-world implementations, in both wired and wireless testbeds. We have in addition compared them with a decade-old variant of RED called Adaptive RED, which shares with CoDel and PIE the goal of “knob-free” operation. Surprisingly, in many instances results were much more favorable towards Adaptive RED. We do not call into question the need for new AQMs, however, there are lessons yet to be learned from old designs.

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