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Evaluating and Reducing Multipath Transport Latency
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science (from 2013).
2019 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

Access to the Internet is a very significant part of everyday life with increasing online services such as news delivery, banking, gaming, audio and high quality movies. Applications require different transport guarantees with some requiring higher bandwidth and others low latency. Upgrading access link capacity does not guarantee faster access to the Internet as it offers higher bandwidth but may not offer low latency. With increasing number of mobile devices supporting more than one access technologies (e.g., WLAN, 3G, 4G,..), there is a need to analyse the impact of using multiple such technologies at the same time. Legacy transport protocols such as TCP or SCTP are only able to connect to one access network at a time to create an end-to-end connection. When more than one access technology is used, there may be a large difference in the data rate offered by each technology. This asymmetry might impact latency sensitive applications by creating out of order delivery. In this thesis, we focus on the latency aspect of multipath transport protocol performance. We consider CMT-SCTP and Multipath TCP as available multipath protocols that were designed for exploiting multiple paths for better throughput and reliability. We consider various real world traffic scenarios such as Video, Gaming and Web traffic to measure end-to-end latency. We perform simulations, emulations and experiments using heterogeneous network settings involving access networks with different bandwidth, delay and loss characteristics. MPTCP performs better in terms of latency than CMT-SCTP and TCP in certain scenarios where available paths are symmetric. However, MPTCP does not perform well in asymmetric scenarios with latency sensitive traffic. This analysis provides insights in to various areas of improvement in MPTCP such as scheduling and loss recovery to achieve low latency. We further focus on packet loss recovery in MPTCP for specific cases of tail losses to reduce latency. Tail losses are the losses that occur at the end of a packet stream. Recovering such losses is of higher significance to latency sensitive applications. We propose a modification to the use of TLP, a mechanism in TCP for tail loss recovery. We evaluate the performance of proposed TLP modification, first using emulations and with real world network experiments. Our results show significant improvements in latency for specific loss scenarios in emulations and up to 50% improvement in experiments.

Abstract [en]

With an increasing number of mobile devices supporting more than one access technologies (e.g., WLAN, 3G, 4G), there is a need to analyse the impact of using multiple such technologies at the same time. The inherent asymmetry among these technologies might affect latency sensitive applications by creating out of order delivery. In this thesis, we consider CMT-SCTP and Multipath TCP as available multipath protocols designed to exploit multiple paths for better throughput and reliability.  We perform simulations, emulations and experiments using various real-world traffic scenarios such as Video, Gaming and Web traffic to measure end-to-end latency. MPTCP performs better in terms of latency than CMT-SCTP and TCP in certain scenarios where available paths are symmetric. This analysis provides insights into various areas of improvement in MPTCP such as scheduling and loss recovery to achieve low latency. We further focus on packet loss recovery in MPTCP for specific cases of tail losses (losses that occur at the end of a packet stream) to reduce latency. This thesis presents a modification to the use of Tail Loss Probe (TLP) in MPTCP that provides improvements in latency for specific loss scenarios in emulations and upto 50% improvement in experiments.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2019. , p. 103
Series
Karlstad University Studies, ISSN 1403-8099 ; 2019:5
National Category
Computer Sciences
Research subject
Computer Science
Identifiers
URN: urn:nbn:se:kau:diva-71223ISBN: 978-91-7867-001-7 (print)ISBN: 978-91-7867-006-2 (electronic)OAI: oai:DiVA.org:kau-71223DiVA, id: diva2:1290554
Presentation
2019-03-21, 1B306, 10:30 (English)
Opponent
Supervisors
Available from: 2019-03-06 Created: 2019-02-20 Last updated: 2019-03-22Bibliographically approved
List of papers
1. Is Multi-Path Transport Suitable for Latency Sensitive Traffic?
Open this publication in new window or tab >>Is Multi-Path Transport Suitable for Latency Sensitive Traffic?
Show others...
2016 (English)In: Computer Networks, ISSN 1389-1286, E-ISSN 1872-7069, Vol. 105, p. 1-21Article in journal (Refereed) Published
Abstract [en]

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. 

Place, publisher, year, edition, pages
Elsevier, 2016
Keywords
Internet; Latency; Multi-path communication; Transport protocols; MPTCP; CMT-SCTP
National Category
Computer and Information Sciences
Research subject
Computer Science
Identifiers
urn:nbn:se:kau:diva-42624 (URN)10.1016/j.comnet.2016.05.008 (DOI)000380869300001 ()
Available from: 2016-06-03 Created: 2016-06-03 Last updated: 2019-07-12Bibliographically approved
2. Probe or Wait: Handling tail losses using Multipath TCP
Open this publication in new window or tab >>Probe or Wait: Handling tail losses using Multipath TCP
2017 (English)In: 2017 IFIP Networking Conference (IFIP Networking) and Workshops, IEEE, 2017Conference paper, Published paper (Refereed)
Abstract [en]

Packet losses are known to affect the performance of latency sensitive Internet applications such as media streaming and gaming. Transport protocols recover from packet loss in order to provide reliable end-to-end communication and improve user experience. The efficiency of loss recovery mechanisms influences the completion time of flows, and thus also the application performance as perceived by the end user. In this paper we focus on state-of-the-art loss recovery mechanisms for TCP and Multipath TCP. We use controlled tail loss scenarios to evaluate the performance of loss recovery mechanisms and, based on the observations, we propose an enhanced tail loss recovery mechanism for Multipath TCP, to improve the loss recovery time. Our experiment results, using the Linux Multipath TCP implementation, show consistent end-to-end latency performance improvement in considered scenarios.

Place, publisher, year, edition, pages
IEEE, 2017
Keywords
MultipathTCP
National Category
Computer Systems Telecommunications Computer Engineering Communication Systems
Research subject
Computer Science
Identifiers
urn:nbn:se:kau:diva-66625 (URN)10.23919/IFIPNetworking.2017.8264885 (DOI)000425452000062 ()978-3-901882-94-4 (ISBN)
Conference
2017 IFIP Networking Conference (IFIP Networking) and Workshops, 12-16 June 2017, Stockholm, Sweden
Available from: 2018-03-08 Created: 2018-03-08 Last updated: 2019-02-21Bibliographically approved
3. Handling Packet Losses in Cloud-Based Application Traffic
Open this publication in new window or tab >>Handling Packet Losses in Cloud-Based Application Traffic
2019 (English)In: Proceedings of the 9th International Conference on Cloud Computing and Services Science - Volume 1: CLOSER, SciTePress, 2019, p. 111-119Conference paper, Published paper (Refereed)
Abstract [en]

Internet traffic is comprised of data flows from various applications with unique traffic characteristics. For many cloud applications, end-to-end latency is a primary factor affecting the perceived user experience. As packet losses cause delays in the communication they impact user experience, making efficient handling of packet losses an important function of transport layer protocols. Multipath TCP (MPTCP) is a modification to TCP that enables simultaneous use of several paths for a TCP flow. MPTCP is known to improve throughput. However, the performance of MPTCP is not optimal when handling certain loss scenarios. Efficient packet loss recovery is thus important to achieve desirable flow completion times for interactive cloud-based applications. In this paper we evaluate the performance of MPTCP in handling tail losses using traffic traces from various cloud-based applications. Tail losses, losses that occur at the end of a flow or traffic burst, are particularly challenging from a latency perspective as they are difficult to detect and recover in a timely manner. Tail losses in TCP are handled by using a tail loss probe (TLP) mechanism which was adapted to MPTCP from TCP. We investigate the performance of TLP in MPTCP, comparing the standard implementation to a recently proposed, less conservative approach. Our experimental results show that a less conservative implementation of TLP performs significantly better than the standard implementation in handling tail losses, reducing the average burst completion time of cloud based applications when tail loss occurs by up to 50% in certain cases.

Place, publisher, year, edition, pages
SciTePress, 2019
Keywords
Multipath TCP, Cloud Applications, Latency, Loss Recovery, Performance Evaluation, Measurements.
National Category
Computer Sciences
Research subject
Computer Science
Identifiers
urn:nbn:se:kau:diva-70749 (URN)10.5220/0007723801110119 (DOI)2-s2.0-85067484825 (Scopus ID)978-989-758-365-0 (ISBN)
Conference
9th International Conference on Cloud Computing and Services Science, CLOSER 2019 2-4 May, Heraklion, Greece
Available from: 2019-02-20 Created: 2019-02-20 Last updated: 2019-07-10Bibliographically approved

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Yedugundla, Kiran

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