RITE: Reducing Internet Transport Latency

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Publications at RITE: Reducing Internet Transport Latency
Journal Article
Online Identification of Groups of Flows Sharing a Network Bottleneck
IEEE/ACM Transactions on Networking 28 (2020): 2229-2242.Status: Published
Online Identification of Groups of Flows Sharing a Network Bottleneck
Abstract—Most Internet hosts today support multiple access technologies and network interfaces. Multipath transport protocols, like MPTCP, are being deployed (e.g., in smartphones), allowing transparent simultaneous use of multiple links. Besides providing increased resilience to link failures, multipath trans- ports may better exploit available (aggregate) capacity across all interfaces. The safest way to ensure fairness is to assume that any subflows of a multipath end-to-end connection may share bottleneck links, but knowledge of non-shared bottlenecks could allow multipath senders to exploit more capacity without being unfair to other flows. The problem of reliably detecting the existence of (non)-shared bottlenecks is not trivial and is compounded by the fact that bottlenecks may change due to traffic dynamics. In this paper we focus on practical methods to reliably group flows that share, possibly dynamic, bottlenecks online and in a passive manner (i.e., without injecting measurement traffic). We introduce a novel dynamic clustering algorithm that we apply to update our previous shared bottleneck flow grouping (SBFG) method standardized by the IETF, based on delay statistics. We also adapt an offline SBFG method based on wavelet filters to enable it for online operation. These SBFG methods are evaluated by a simple testbed, rigorous simulation and real-world Internet experiments in a testbed comprised of multihomed hosts. Our results suggest that there is no clear winner, and selection of the “best” SBFG method will have to consider tradeoffs regarding accuracy, lag, and application requirements.
Afilliation | Communication Systems |
Project(s) | RITE: Reducing Internet Transport Latency, Department of Mobile Systems and Analytics, The Center for Resilient Networks and Applications |
Publication Type | Journal Article |
Year of Publication | 2020 |
Journal | IEEE/ACM Transactions on Networking |
Volume | 28 |
Number | 5 |
Pagination | 2229--2242 |
Publisher | IEEE/ACM |
ISSN | Print ISSN: 1063-6692, Electronic ISSN: 1558-2566 |
Keywords | dynamic clustering, Internet congestion control, multipath congestion control., shared bottleneck detection |
Notes | Published in the Early Access area on IEEE Xplore. The content is final as presented with the exception of pagination and |
DOI | 10.1109/TNET.2020.3007346 |
Miscellaneous
Shared Bottleneck Detection for Coupled Congestion Control for RTP Media
In RFC 8382. Internet Requests for Comments ed. RFC Editor, 2018.Status: Published
Shared Bottleneck Detection for Coupled Congestion Control for RTP Media
This document describes a mechanism to detect whether end-to-end data flows share a common bottleneck. This mechanism relies on summary statistics that are calculated based on continuous measurements and used as input to a grouping algorithm that runs wherever the knowledge is needed
Afilliation | Communication Systems |
Project(s) | RITE: Reducing Internet Transport Latency |
Publication Type | Miscellaneous |
Year of Publication | 2018 |
Publisher | RFC Editor |
Notes | Internet Engineering Task Force (IETF) Request for Comments: 8382 Category: Experimental ISSN: 2070-1721 |
URL | https://www.rfc-editor.org/info/rfc8382 |
DOI | 10.17487/RFC8382 |
TR-Number | 8382 |
Journal Article
Operating ranges, tunability and performance of CoDel and PIE
Computer Communications 103 (2017): 74-82.Status: Published
Operating ranges, tunability and performance of CoDel and PIE
Bufferbloat is excessive delay due to the accumulation of packets in a router’s oversized queues. CoDel and PIE are two recent Active Queue Management (AQM) algorithms that have been proposed to address bufferbloat by reducing the queuing delay while trying to maintain a high bottleneck utilization. This paper fills a gap by outlining what are the operating ranges, that is the network characteristics (in terms of round-trip times and bottleneck capacity), for which these algorithms achieve their design goals. This new approach to the problem lets us identify deployment scenarios where both AQM schemes result in poor performance when used with default parameters. Because PIE and CoDel have been proposed with RED’s deployment issues in mind, it was essential to evaluate to what extent we can tune them to achieve various trade-offs and let them control the queuing delay outside their default operating range. We find that, by appropriate tuning (1) the amount of buffering can easily be controlled with PIE, (2) the Round Trip Time (RTT) sensitivity of CoDel can be reduced. Also, we observe there is more correlation between the congestion level, the achieved queuing delay and the targeted delay with CoDel than with PIE. This paper therefore concludes there is no single overall best AQM scheme, as each scheme proposes a specific trade-off.
Afilliation | Communication Systems |
Project(s) | RITE: Reducing Internet Transport Latency |
Publication Type | Journal Article |
Year of Publication | 2017 |
Journal | Computer Communications |
Volume | 103 |
Pagination | 74-82 |
Date Published | 05/2017 |
Publisher | Elsevier |
Keywords | AQM, Bufferbloat, CoDel, congestion control, PIE |
DOI | 10.1016/j.comcom.2016.07.013 |
Proceedings, refereed
Alternative Backoff: Achieving Low Latency and High Throughput with ECN and AQM
In IFIP Networking. IFIP, 2017.Status: Published
Alternative Backoff: Achieving Low Latency and High Throughput with ECN and AQM
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.
Afilliation | Communication Systems |
Project(s) | RITE: Reducing Internet Transport Latency |
Publication Type | Proceedings, refereed |
Year of Publication | 2017 |
Conference Name | IFIP Networking |
Publisher | IFIP |
Keywords | AQM, congestion control, ECN, low latency, tcp |
Notes | Best Paper Award |
URL | http://dl.ifip.org/db/conf/networking/networking2017/1570335770.pdf |
Talks, invited
Multi-Path Transport with OMNeT++ and the INET Framework
In Albacete, Castilla-La Mancha, Spain. Albacete, Castilla-La Mancha, Spain, 2017.Status: Published
Multi-Path Transport with OMNeT++ and the INET Framework
In order to evaluate the performance of multi-path transport protocols, a straightforward initial step is to perform simulations. OMNeT++, together with the INET Framework, provide a powerful Open Source platform for running network simulations. This talk provides an overview of simulating multi-path transport with OMNeT++ and the INET Framework. Particular focus is on the Concurrent Multipath Transfer extension for the Stream Control Transmission Protocol (SCTP). Furthermore, useful additions like the NetPerfMeter application model, the extended network auto-configurator as well as the Simulation Processing Tool-Chain (SimProcTC) are explained.
Afilliation | Communication Systems |
Project(s) | NorNet, RITE: Reducing Internet Transport Latency |
Publication Type | Talks, invited |
Year of Publication | 2017 |
Location of Talk | Albacete, Castilla-La Mancha, Spain |
Place Published | Albacete, Castilla-La Mancha, Spain |
Keywords | CMT, CMT-SCTP, Concurrent Multipath Transfer, INET Framework, Multi-Path Transport, NetPerfMeter, OMNeT++, SCTP, SimProcTC, Stream Control Transmission Protocol |
Technical reports
TRILL: ECN (Explicit Congestion Notification) Support
Internet Engineering Task Force, 2017.Status: Accepted
TRILL: ECN (Explicit Congestion Notification) Support
Explicit congestion notification (ECN) allows a forwarding element to notify downstream devices, including the destination, of the onset of congestion without having to drop packets. This document extends this capability to TRILL switches, including integration with IP ECN.
Afilliation | Communication Systems |
Project(s) | RITE: Reducing Internet Transport Latency, TimeIn: Traffic behaviour of interactive time-dependent thin streams on the modern Internet |
Publication Type | Technical reports |
Year of Publication | 2017 |
Number | draft-ietf-trill-ecn-support-02 |
Date Published | 03/2017 |
Publisher | Internet Engineering Task Force |
Keywords | Architecture, congestion, Control, Data Communication, Encapsulation, Explicit Notification, Incremental Deployment, Internet, Layering, networks, Protocol Engineering, QoS, Tunnels |
Notes | (Work in Progress) |
URL | http://tools.ietf.org/html/draft-ietf-trill-ecn-support |
Guidelines for Adding Congestion Notification to Protocols that Encapsulate IP
IETF, 2017.Status: Accepted
Guidelines for Adding Congestion Notification to Protocols that Encapsulate IP
Afilliation | Communication Systems |
Project(s) | The Center for Resilient Networks and Applications, RITE: Reducing Internet Transport Latency |
Publication Type | Technical reports |
Year of Publication | 2017 |
Number | draft-ietf-tsvwg-ecn-encap-guidelines-08 |
Publisher | IETF |
Keywords | Architecture, congestion, Control, Data Communication, Encapsulation, Explicit Notification, Internet, Layering, Management, Monitoring, networks, Protocol Engineering, QoS, Tunnels |
Notes | (Work in Progress) |
URL | http://tools.ietf.org/html/draft-ietf-tsvwg-ecn-encap-guidelines |
Journal Article
Is Multi-Path Transport Suitable for Latency Sensitive Traffic?
Computer Networks (COMNET) 105 (2016): 1-21.Status: Published
Is Multi-Path Transport Suitable for Latency Sensitive Traffic?
This paper assesses whether multi-path communication can help latency-sensitive applications to satisfy the requirements of their users. We consider Concurrent Multi-path Transfer for SCTP (CMT-SCTP) and Multi-path TCP (MPTCP) and evaluate their proficiency in transporting video, gaming, and web traffic over combinations of WLAN and 3G interfaces. To ensure the validity of our evaluation, several experimental approaches were used including simulation, emulation and live experiments. When paths are symmetric in terms of capacity, delay and loss rate, we find that the experienced latency is significantly reduced, compared to using a single path. Using multiple asymmetric paths does not affect latency -- applications do not experience any increase or decrease, but might benefit from other advantages of multi-path communication. In the light of our conclusions, multi-path transport is suitable for latency-sensitive traffic and mature enough to be widely deployed.
Afilliation | , Communication Systems, Communication Systems |
Project(s) | NorNet, RITE: Reducing Internet Transport Latency, The Center for Resilient Networks and Applications |
Publication Type | Journal Article |
Year of Publication | 2016 |
Journal | Computer Networks (COMNET) |
Volume | 105 |
Pagination | 1-21 |
Date Published | 08/2016 |
Publisher | Elsevier |
Keywords | CMT-SCTP, Internet, latency, MPTCP, Multi-Path Communication, transport protocols |
DOI | 10.1016/j.comnet.2016.05.008 |
Proceedings, refereed
Managing real-time media flows through a flow state exchange
In NOMS 2016 IEEE/IFIP Network Operations and Management Symposium, 2016.Status: Published
Managing real-time media flows through a flow state exchange
When multiple congestion controlled flows traverse the same network path, their resulting rate is usually an outcome of their competition at the bottleneck. The WebRTC / RTCWeb suite of standards for inter-browser communication is required to allow prioritization. This is addressed by our previously presented mechanism for coupled congestion control, called the Flow State Exchange (FSE). Here, we present our first simulation results using two mechanisms that have been proposed for IETF standardization: Google Congestion Control (GCC) and Network-Assisted Dynamic Adaptation (NADA). These two mechanisms exhibit aspects that allow us to use a simpler “passive” algorithm in our FSE. Passive coupling allows a less time-constrained request-response style of signaling between congestion control mechanisms and the FSE, which enables the FSE to run as a stand-alone management tool.
Afilliation | Communication Systems |
Project(s) | RITE: Reducing Internet Transport Latency |
Publication Type | Proceedings, refereed |
Year of Publication | 2016 |
Conference Name | NOMS 2016 IEEE/IFIP Network Operations and Management Symposium |
Pagination | 112--120 |
Date Published | 04/2016 |
DOI | 10.1109/NOMS.2016.7502803 |
PI2 : A Linearized AQM for both Classic and Scalable TCP
In Proc. ACM CoNEXT 2016. New York, NY, USA: ACM, 2016.Status: Published
PI2 : A Linearized AQM for both Classic and Scalable TCP
This paper concerns the use of Active Queue Management (AQM) to reduce queuing delay. It offers insight into why it has proved hard for a Proportional Integral (PI) controller to remain both responsive and stable while controlling `Classic' TCP flows, such as TCP Reno and Cubic. Due to their non-linearity, the controller's adjustments have to be smaller when the target drop probability is lower. The PI Enhanced (PIE) algorithm attempts to solve this problem by scaling down the adjustments of the controller using a look-up table. Instead, we control an internal variable that is by definition linearly proportional to the load, then post-process it into the required Classic drop probability---in fact we show that the output simply needs to be squared. This allows tighter control, giving responsiveness and stability better or no worse than PIE achieves, but without all its corrective heuristics.
With suitable packet classification, it becomes simple to extend this PI2 AQM to support coexistence between Classic and Scalable congestion controls in the public Internet. A Scalable congestion control ensures sufficient feedback at any flow rate, an example being Data Centre TCP (DCTCP). A Scalable control is linear, so we can use the internal variable directly without any squaring, by omitting the post-processing stage.
We implemented PI2 as a Linux qdisc to extensively test our claims using Classic and Scalable TCPs.
Afilliation | Communication Systems |
Project(s) | RITE: Reducing Internet Transport Latency, TimeIn: Traffic behaviour of interactive time-dependent thin streams on the modern Internet |
Publication Type | Proceedings, refereed |
Year of Publication | 2016 |
Conference Name | Proc. ACM CoNEXT 2016 |
Pagination | 105-119 |
Date Published | 12/2016 |
Publisher | ACM |
Place Published | New York, NY, USA |
ISBN Number | 978-1-4503-4297-1 |
Keywords | Algorithms, Analysis, AQM, Congestion Avoidance, congestion control, Data Communication, Design, Evaluation, Internet, latency, networks, Performance, QoS, Scaling, tcp |
URL | http://dl.acm.org/citation.cfm?doid=2999572.2999578 |
DOI | 10.1145/2999572.2999578 |