Measuring the State of ECN Readiness in Servers, Clients, and Routers

Proceedings of the Eleventh ACM SIGCOMM/USENIX Internet Measurement Conference (IMC 2011), Berlin, DE, November 2011.Better exposing congestion can improve traffic management in the wide-area, at peering points, among residential broadband connections, and in the data center. TCP's network utilization and efficiency depends on congestion information, while recent research proposes economic and policy models based on congestion. Such motivations have driven widespread support of Explicit Congestion Notification (ECN) in modern operating systems. We reappraise the Internet's ECN readiness, updating and extending previous measurements. Across large and diverse server populations, we find a three-fold increase in ECN support over prior studies. Using new methods, we characterize ECN within mobile infrastructure and at the client-side, populations previously unmeasured. Via large-scale path measurements, we find the ECN feedback loop failing in the core of the network 40\% of the time, typically at AS boundaries. Finally, we discover new examples of infrastructure violating ECN Internet standards, and discuss remaining impediments to running ECN while suggesting mechanisms to aid adoption

Is Explicit Congestion Notification usable with UDP?

We present initial measurements to determine if ECN is usable with UDP traffic in the public Internet. This is interesting because ECN is part of current IETF proposals for congestion control of UDPbased interactive multimedia, and due to the increasing use of UDP as a substrate on which new transport protocols can be deployed. Using measurements from the author’s homes, their workplace, and cloud servers in each of the nine EC2 regions worldwide, we test reachability of 2500 servers from the public NTP server pool, using ECT(0) and not-ECT marked UDP packets. We show that an average of 98.97% of the NTP servers that are reachable using not-ECT marked packets are also reachable using ECT(0) marked UDP packets, and that ~98% of network hops pass ECT(0) marked packets without clearing the ECT bits. We compare reachability of the same hosts using ECN with TCP, finding that 82.0% of those reachable with TCP can successfully negotiate and use ECN. Our findings suggest that ECN is broadly usable with UDP traffic, and that support for use of ECN with TCP has increased

ECN with QUIC: Challenges in the Wild

TCP and QUIC can both leverage ECN to avoid congestion loss and its retransmission overhead. However, both protocols require support of their remote endpoints and it took two decades since the initial standardization of ECN for TCP to reach 80% ECN support and more in the wild. In contrast, the QUIC standard mandates ECN support, but there are notable ambiguities that make it unclear if and how ECN can actually be used with QUIC on the Internet. Hence, in this paper, we analyze ECN support with QUIC in the wild: We conduct repeated measurements on more than 180M domains to identify HTTP/3 websites and analyze the underlying QUIC connections w.r.t. ECN support. We only find 20% of QUIC hosts, providing 6% of HTTP/3 websites, to mirror client ECN codepoints. Yet, mirroring ECN is only half of what is required for ECN with QUIC, as QUIC validates mirrored ECN codepoints to detect network impairments: We observe that less than 2% of QUIC hosts, providing less than 0.3% of HTTP/3 websites, pass this validation. We identify possible root causes in content providers not supporting ECN via QUIC and network impairments hindering ECN. We thus also characterize ECN with QUIC distributedly to traverse other paths and discuss our results w.r.t. QUIC and ECN innovations beyond QUIC.Comment: Accepted at the ACM Internet Measurement Conference 2023 (IMC'23

MUST, SHOULD, DON'T CARE: TCP Conformance in the Wild

Standards govern the SHOULD and MUST requirements for protocol implementers for interoperability. In case of TCP that carries the bulk of the Internets' traffic, these requirements are defined in RFCs. While it is known that not all optional features are implemented and nonconformance exists, one would assume that TCP implementations at least conform to the minimum set of MUST requirements. In this paper, we use Internet-wide scans to show how Internet hosts and paths conform to these basic requirements. We uncover a non-negligible set of hosts and paths that do not adhere to even basic requirements. For example, we observe hosts that do not correctly handle checksums and cases of middlebox interference for TCP options. We identify hosts that drop packets when the urgent pointer is set or simply crash. Our publicly available results highlight that conformance to even fundamental protocol requirements should not be taken for granted but instead checked regularly

Informing protocol design through crowdsourcing measurements

Mención Internacional en el título de doctorMiddleboxes, such as proxies, firewalls and NATs play an important role in the modern Internet ecosystem. On one hand, they perform advanced functions, e.g. traffic shaping, security or enhancing application performance. On the other hand, they turn the Internet into a hostile ecosystem for innovation, as they limit the deviation from deployed protocols. It is therefore essential, when designing a new protocol, to first understand its interaction with the elements of the path. The emerging area of crowdsourcing solutions can help to shed light on this issue. Such approach allows us to reach large and different sets of users and also different types of devices and networks to perform Internet measurements. In this thesis, we show how to make informed protocol design choices by expanding the traditional crowdsourcing focus from the human element and using crowdsourcing large scale measurement platforms. We consider specific use cases, namely the case of pervasive encryption in the modern Internet, TCP Fast Open and ECN++. We consider such use cases to advance the global understanding on whether wide adoption of encryption is possible in today’s Internet or the adoption of encryption is necessary to guarantee the proper functioning of HTTP/2. We target ECN and particularly ECN++, given its succession of deployment problems. We then measured ECN deployment over mobile as well as fixed networks. In the process, we discovered some bad news for the base ECN protocol—more than half the mobile carriers we tested wipe the ECN field at the first upstream hop. This thesis also reports the good news that, wherever ECN gets through, we found no deployment problems for the ECN++ enhancement. The thesis includes the results of other more in-depth tests to check whether servers that claim to support ECN, actually respond correctly to explicit congestion feedback, including some surprising congestion behaviour unrelated to ECN. This thesis also explores the possible causes that ossify the modern Internet and make difficult the advancement of the innovation. Network Address Translators (NATs) are a commonplace in the Internet nowadays. It is fair to say that most of the residential and mobile users are connected to the Internet through one or more NATs. As any other technology, NAT presents upsides and downsides. Probably the most acknowledged downside of the NAT technology is that it introduces additional difficulties for some applications such as peer-to-peer applications, gaming and others to function properly. This is partially due to the nature of the NAT technology but also due to the diversity of behaviors of the different NAT implementations deployed in the Internet. Understanding the properties of the currently deployed NAT base provides useful input for application and protocol developers regarding what to expect when deploying new application in the Internet. We develop NATwatcher, a tool to test NAT boxes using a crowdsourcingbased measurement methodology. We also perform large scale active measurement campaigns to detect CGNs in fixed broadband networks using NAT Revelio, a tool we have developed and validated. Revelio enables us to actively determine from within residential networks the type of upstream network address translation, namely NAT at the home gateway (customer-grade NAT) or NAT in the ISP (Carrier Grade NAT). We deploy Revelio in the FCC Measuring Broadband America testbed operated by SamKnows and also in the RIPE Atlas testbed. A part of this thesis focuses on characterizing CGNs in Mobile Network Operators (MNOs). We develop a measuring tool, called CGNWatcher that executes a number of active tests to fully characterize CGN deployments in MNOs. The CGNWatcher tool systematically tests more than 30 behavioural requirements of NATs defined by the Internet Engineering Task Force (IETF) and also multiple CGN behavioural metrics. We deploy CGNWatcher in MONROE and performed large measurement campaigns to characterize the real CGN deployments of the MNOs serving the MONROE nodes. We perform a large measurement campaign using the tools described above, recruiting over 6,000 users, from 65 different countries and over 280 ISPs. We validate our results with the ISPs at the IP level and, reported to the ground truth we collected. To the best of our knowledge, this represents the largest active measurement study of (confirmed) NAT or CGN deployments at the IP level in fixed and mobile networks to date. As part of the thesis, we characterize roaming across Europe. The goal of the experiment was to try to understand if the MNO changes CGN while roaming, for this reason, we run a series of measurements that enable us to identify the roaming setup, infer the network configuration for the 16 MNOs that we measure and quantify the end-user performance for the roaming configurations which we detect. We build a unique roaming measurement platform deployed in six countries across Europe. Using this platform, we measure different aspects of international roaming in 3G and 4G networks, including mobile network configuration, performance characteristics, and content discrimination. We find that operators adopt common approaches to implementing roaming, resulting in additional latency penalties of 60 ms or more, depending on geographical distance. Considering content accessibility, roaming poses additional constraints that leads to only minimal deviations when accessing content in the original country. However, geographical restrictions in the visited country make the picture more complicated and less intuitive. Results included in this thesis would provide useful input for application, protocol designers, ISPs and researchers that aim to make their applications and protocols to work across the modern Internet.Programa de Doctorado en Ingeniería Telemática por la Universidad Carlos III de MadridPresidente: Gonzalo Camarillo González.- Secretario: María Carmen Guerrero López.- Vocal: Andrés García Saavedr

A middlebox-cooperative TCP for a non end-to-end Internet. In

ABSTRACT Understanding, measuring, and debugging IP networks, particularly across administrative domains, is challenging. One particularly daunting aspect of the challenge is the presence of transparent middleboxes-which are now common in today's Internet. In-path middleboxes that modify packet headers are typically transparent to a TCP, yet can impact end-to-end performance or cause blackholes. We develop TCP HICCUPS to reveal packet header manipulation to both endpoints of a TCP connection. HICCUPS permits endpoints to cooperate with currently opaque middleboxes without prior knowledge of their behavior. For example, with visibility into end-to-end behavior, a TCP can selectively enable or disable performance enhancing options. This cooperation enables protocol innovation by allowing new IP or TCP functionality (e.g., ECN, SACK, Multipath TCP, Tcpcrypt) to be deployed without fear of such functionality being misconstrued, modified, or blocked along a path. HICCUPS is incrementally deployable and introduces no new options. We implement and deploy TCP HICCUPS across thousands of disparate Internet paths, highlighting the breadth and scope of subtle and hard to detect middlebox behaviors encountered. We then show how path diagnostic capabilities provided by HICCUPS can benefit applications and the network

Migration to a New Internet Protocol in Operator Network

This thesis explains the differences between IPv4 and IPv6. Another important part of the thesis is to review the current readiness of IPv6 for worldwide production use. The status (in terms of readiness, adaptability, compatibility and co-existence) of IPv6 in TeliaSonera is discussed in more detail. The most important reason for migrating to IPv6 is the address exhaustion of IPv4. This may not be a big problem in the developed countries but in developing countries the growth of Internet is fast and lots of more addresses are needed. The need for addresses is not only from computers but from many devices connected to the Internet. Attempts to slow down the exhaustion of free addresses have been made but current solutions are not enough. IPv6 will solve the problem by using much longer addresses. It will also add security features and simplify headers to speed up routing. TeliaSonera has started to roll out IPv6 services. At the beginning the corporate customers will receive IPv6 connectivity and consumers will follow later. TeliaSonera International Carrier is already serving its customers with IPv6. It seems that IPv6 is ready, standards have been ready for years and support in devices and software is prevalent. To achieve and keep up the global connectivity, IPv6 is a must and should not be avoided

Internet QoS for DiffServ-Enabled Routers

Differentiated Service Model (DiffServ) is currently a popular research topic as a low-cost method to bring QoS to today's Internet backbone network. In this paper, the author introduces the techniques and methodologies that used to design and implement DiffServ-enabled (DS-enabled) routers. The adaptations of DS-enabled routers are designed to cater to the low Internet connectivity within Universiti Teknologi PETRONAS LAN. The author has implemented basic DiffServ setting using three CISC03725 routers. Based on these DiffServ-enabled routers, the author set up a small scale lab network to study DiffServ QoS features: priority dropping (discrimination among different service classes), QoS guarantees and measuring QoS using various formal metrics (delay and throughput). Furthermore, the author present problems encountered during study, and the proposed solutions

SURVEI MEKANISME CONGESTION KONTROL PADA TRANSMISSION CONTROL PROTOCOL DI SOFTWARE DEFINED NETWORK

Sebuah paradigma baru jaringan, Software Defined Network (SDN) dikembangkan membagi integrasi vertikal dalam perangkat jaringan, memisahkan logika kontrol dari infrastruktur jaringan sehingga memungkinkan untuk mengubah keadaan dan kondisi jaringan dari pengontrol yang dapat diprogram secara terpusat. sebagian besar komunikasi one-to-many pada SDN diimplementasikan melalui beberapa unicast seperti TCP, yang tidak efisien. Hal itu menghasilkan banyak trafik direplikasi, yang dapat berakibat menurunkan kinerja aplikasi karena beberapa permasalahan seperti congestion, redundancy dan collision. Permasalahan congestion terjadi ketika sebuah network mempunyai beban yang banyak dan mengakibatkan performansi menurun karena jumlah pengiriman melebihi kapasitas router yang ada. Salah satu solusi penanganan congesti dengan mereduksi ukuran TCP receive window. Tujuan utama dari pembuatan makalah ini adalah merangkum beberapa mekanisme kontrol kemacetan menggunakan TCP yang telah diakukan oleh para peneliti untuk menangani permasalahan kemacetan pada jaringan