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Latency Reduction for Soft Real-Time Traffic using SCTP Multihoming
Karlstad University, Faculty of Health, Science and Technology (starting 2013), Department of Mathematics and Computer Science. Karlstad University. (DISCO)ORCID iD: 0000-0002-6723-881X
2016 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

More and more so-called soft real-time traffic is being sent over IP-based networks. The bursty, data-limited traffic pattern as well as the latency requirements from this traffic present challenges to the traditional communication techniques, designed for bulk traffic without considering latency.

To meet the requirements from soft real-time traffic, in particular from telephony signaling, the Stream Control Transmission Protocol (SCTP) was designed. Its support for connectivity to multiple networks, i.e., multihoming, provides robustness and opens up for concurrent multipath transfer (CMT) over multiple paths. Since SCTP is a general transport protocol, it also enables for handover of media sessions between heterogeneous networks. Migrating an ongoing session to a new network, as well as CMT with minimal latency, requires tuning of several protocol parameters and mechanisms.

This thesis addresses latency reduction for soft real-time traffic using SCTP multihoming from three perspectives. The first focus is on latency for signaling traffic in case of path failure, where a path switch, a failover, occurs. We regard quick failure detection as well as rapid startup on the failover target path. The results indicate that by careful parameter tuning, the failover time may be significantly reduced. The second focus in the thesis is on latency for signaling traffic using CMT. To this end, we address sender-side scheduling. We evaluate some existing schedulers, and design a dynamic stream-aware scheduler. The results indicate that the dynamic stream-aware scheduler may provide significantly improved latency in unbalanced networks. Finally, we target multihomed SCTP to provide for handover of a media session between heterogeneous wireless networks in a mobile scenario. We implement a handover scheme and our investigation shows that SCTP could provide for seamless handover of a media session at walking speed.

Abstract [en]

So-called soft real-time traffic may be sent over IP-based networks. The bursty, data-limited traffic pattern and the latency requirements from this traffic present a challenge to traditional communication techniques. The Stream Control Transmission Protocol (SCTP), with support for multihoming, was designed to better meet the requirements from soft-real time traffic. Multihoming provides for robustness and for concurrent multipath transfer (CMT) as well as for handover of sessions between heterogeneous networks. Still, to meet the timeliness requirements, tuning of protocol parameters and mechanisms is crucial.

This thesis addresses latency reduction for soft real-time traffic using SCTP multihoming. The first focus is on signaling traffic in case of path failure, where a path switch, a failover, occurs. We show that careful parameter tuning may reduce the failover time significantly. The second focus is on signaling traffic using CMT. We address sender-side scheduling and show that dynamic stream-aware scheduling may reduce latency when data is transmitted over asymmetric network  paths. The third focus is multihomed SCTP for handover between heterogeneous networks, where we show that SCTP could provide for seamless handover of a media session at walking speed.

Place, publisher, year, edition, pages
Karlstad: Karlstad University Press, 2016. , p. 34
Series
Karlstad University Studies, ISSN 1403-8099 ; 2016:14
Keyword [en]
transport protocol, SCTP, multihoming, latency, performance evaluation, failover, concurrent multipath transfer, scheduling, mobility, handover
National Category
Computer Sciences
Research subject
Computer Science
Identifiers
URN: urn:nbn:se:kau:diva-40713ISBN: 978-91-7063-693-6 (print)OAI: oai:DiVA.org:kau-40713DiVA, id: diva2:906958
Public defence
2016-06-17, 21A342, Karlstad, 09:30 (English)
Opponent
Supervisors
Note

Paper 3 (Efficient Scheduling to Reduce Latency...) ingick i avhandlingen som manuskript med samma namn.

Available from: 2016-05-18 Created: 2016-02-25 Last updated: 2018-01-10Bibliographically approved
List of papers
1. On the Relation Between SACK Delay and SCTP Failover Performance for Different Traffic Distributions
Open this publication in new window or tab >>On the Relation Between SACK Delay and SCTP Failover Performance for Different Traffic Distributions
2008 (English)In: Proceedings on the Fifth International Conference on Broadband Communications, Networks and Systems, IEEE , 2008, p. 577-584Conference paper, Published paper (Refereed)
Abstract [en]

The stream control transmission protocol (SCTP) is an important component in the ongoing evolution towards IP in the fixed and mobile telephone networks. It is the transport protocol being used in the ongoing deployment of IETFpsilas signaling transport (SIGTRAN) architecture for tunneling of traditional telephony signaling traffic over IP. Further SCTP represents an alternative for future SIP signaling traffic. Key to the success of SCTP is its ability to recover from network failures, in particular failed network paths. SCTP includes multihoming and a failover mechanism which should swiftly shift from a failed or unavailable network path to a backup path. However, several studies have shown that SCTPpsilas failover performance is dependent on factors both related to protocol parameters and network conditions. This paper complements these studies by providing a comprehensive evaluation of the impact of SACK delay under various traffic distributions. The results show a clear relation between the traffic distribution and the impact of the SACK delay on SCTP failover performance. Severe negative effects are observed for low intensity traffic composed of individual signaling messages. On the other hand, our results show limited impact of SACK delay for high intensity and bursty traffic. Furthermore, the results show a limited increase in network traffic by reducing the SACK delay at low traffic intensities and even less impact on network traffic at high traffic intensities. Based on these results we recommend a decrease of the SCTP SACK timer to a small value in signaling scenarios

Place, publisher, year, edition, pages
IEEE, 2008
Keyword
Communication system traffic control, Computer science, Delay, Mobile computing, TCPIP, Telecommunication traffic, Telephony, Time division multiplexing, Transport protocols, Tunneling
National Category
Computer Systems
Research subject
Computer Science
Identifiers
urn:nbn:se:kau:diva-5690 (URN)10.1109/BROADNETS.2008.4769145 (DOI)978-1-4244-2391-0 (ISBN)
Conference
BROADNETS 2008 Fifth International Conference on Broadband Communications, Networks and Systems, 8-11 Sept. 2008, London
Available from: 2010-06-01 Created: 2010-06-01 Last updated: 2017-12-06Bibliographically approved
2. Tuning SCTP Failover for Carrier Grade Telephony Signaling
Open this publication in new window or tab >>Tuning SCTP Failover for Carrier Grade Telephony Signaling
2010 (English)In: Computer Networks, ISSN 1389-1286, E-ISSN 1872-7069, Vol. 54, no 1, p. 133-149Article in journal (Refereed) Published
Abstract [en]

The Stream Control Transmission Protocol (SCTP) has not only been selected as the signaling transport protocol of choice in IETF SIGTRAN, the architecture that bridges circuit-switched and IP-based mobile core networks, but also plays a pivotal role in SAE/LTE, the next-generation UMTS/HSPA networks. To meet the redundancy requirements of telecom signaling traffic, SCTP includes a failover mechanism that enables rerouting of traffic from an unreachable network path to a backup path. However, the recommendations provided by IETF on how to configure the SCTP failover mechanism to meet telecom signaling requirements are kept quite general and leave much of the tuning to the telecom equipment vendor and/or operator. Several works by us and others have been carried out to study the effect of different SCTP parameters on the failover performance. The main contribution of this paper is that it gives a coherent treatment of how to configure the SCTP failover mechanism for carrier-grade telephony signaling, and provides practically usable configuration recommendations. The paper also discusses an alternate or complementary way of optimizing the SCTP failover mechanism by relaxing the exponential backoff that foregoes a retransmission timeout in SCTP. Some results showing significantly reduced failover times by use of this mechanism, with only marginal deteriorating effects on a signaling network, are discussed and analyzed in the paper.

Place, publisher, year, edition, pages
Elsevier, 2010
Keyword
SCTP, Reliable transport protocol, Robustness, Failover performance
National Category
Computer Systems
Research subject
Computer Science
Identifiers
urn:nbn:se:kau:diva-5692 (URN)10.1016/j.comnet.2009.08.016 (DOI)
Available from: 2010-06-01 Created: 2010-06-01 Last updated: 2017-12-12Bibliographically approved
3. Efficient Scheduling to Reduce Latency for Signaling Traffic using CMT-SCTP
Open this publication in new window or tab >>Efficient Scheduling to Reduce Latency for Signaling Traffic using CMT-SCTP
2016 (English)In: 27th Annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), September 4-7, Valencia, Spain, IEEE Communications Society, 2016Conference paper, Published paper (Refereed)
Abstract [en]

To mitigate delay spikes during transmission of bursty signaling traffic, concurrent multipath transmission (CMT) over several paths in parallel could be an option. Still, unordered delivery is a well known problem when concurrently transmitting data over asymmetric network paths, leading to extra delay due to Head-of-Line Blocking (HoLB). The Stream Control Transmission Protocol (SCTP), designed as a carrier for signaling traffic over IP, is currently being extended with support for CMT (CMT-SCTP). To reduce the impact of HoLB, SCTP has support for transmission of separate data flows, called SCTP streams. In this paper, we address sender scheduling to optimize latency for signaling traffic using CMT-SCTP. We present dynamic stream-aware (DS) scheduling, which utilizes the SCTP stream concept, and continuously considers the current network status as well as the data load to make scheduling decisions. We implement a DS scheduler and compare it against some existing schedulers. Our investigation suggests that DS scheduling could significantly reduce latency compared to dynamic path scheduling that does not consider streams. Moreover, we show that naive round-robin scheduling may provide low latency over symmetric network paths, but may transmit data on non-beneficial asymmetric network paths leading to increased latency. Finally, our results show that a static stream based approach, found beneficial for bulk traffic, is not appropriate for bursty signaling traffic. 

Place, publisher, year, edition, pages
IEEE Communications Society, 2016
Keyword
CMT-SCTP, real-time traffic, latency; scheduling, signaling, QoS
National Category
Telecommunications
Research subject
Computer Science
Identifiers
urn:nbn:se:kau:diva-42634 (URN)000391598800361 ()
Conference
27th Annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC) September 4-7, Valencia, Spain
Projects
HITS
Funder
Knowledge Foundation
Available from: 2016-06-07 Created: 2016-06-07 Last updated: 2017-12-06Bibliographically approved
4. Theoretical Analysis of an Ideal Startup Scheme in Multihomed SCTP
Open this publication in new window or tab >>Theoretical Analysis of an Ideal Startup Scheme in Multihomed SCTP
2010 (English)In: Networked Services and Applications - Engineering, Control and Management: 16th EUNICE/IFIP WG 6.6 Workshop, EUNICE 2010, Trondheim, Norway, June 28-30, 2010 / [ed] Finn Arve Aagesen, Svein Johan Knapskog, Springer , 2010, p. 155-166Conference paper, Published paper (Refereed)
Abstract [en]

SCTP congestion control includes the slow-start mechanism to probe the network for available bandwidth. In case of a path switch in a multihomed association, this mechanism may cause a sudden drop in throughput and increased message delays. By estimating the available bandwidth on the alternate path it is possible to utilize a more efficient startup scheme. In this paper, we analytically compare and quantify the degrading impact of slow start in relation to an ideal startup scheme. We consider three different scenarios where a path switch could occur. Further, we identify relevant traffic for these scenarios. Our results point out that the most prominent performance gain is seen for applications generating high traffic loads, like video conferencing. For this traffic, we have seen reductions in transfer time of more than 75% by an ideal startup scheme. Moreover, the results show an increasing impact of an improved startup mechanism with increasing RTTs

Place, publisher, year, edition, pages
Springer, 2010
Series
Lecture Notes in Computer Science, ISSN 0302-9743 ; 6164
National Category
Computer Systems
Research subject
Computer Science
Identifiers
urn:nbn:se:kau:diva-5693 (URN)10.1007/978-3-642-13971-0 (DOI)978-3-642-13970-3 (ISBN)
Conference
Engineering, Control and Management Conference - 16th EUNICE/IFIP WG 6.6 Workshop, EUNICE 2010, Trondheim, Norway, June 28-30, 2010
Note
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xAvailable from: 2010-06-01 Created: 2010-06-01 Last updated: 2017-12-06Bibliographically approved
5. Impact of Slow Start on SCTP Handover Performance
Open this publication in new window or tab >>Impact of Slow Start on SCTP Handover Performance
Show others...
2011 (English)In: Proceedings of 20th International Conference on Computer Communications and Networks: ICCCN2011, IEEE conference proceedings, 2011Conference paper, Published paper (Refereed)
Abstract [en]

The rapidly growing interest in untethered Internet connections, especially in terms of WLAN and 3G/4G mobile connections, calls for intelligent session management: a mobile device should be able to provide a reasonable end-user experience despite location changes, disconnection periods and, not least, handovers. As part of an effort to develop a SCTP-based session management framework that meets these criteria, we are studying ways of improving the SCTP handover delay for real-time traffic; especially the startup delay on the connection between a mobile device and the target access point. To obtain an appreciation of the theoretically feasible gains of optimizing the startup delay on the handover-target path, we have developed a model that predicts the transfer times of SCTP messages during slow start. This paper experimentally validates our model and demonstrates that it could be used to predict the message transfer times in a variable bitrate flow by approximating the variable flow with a constant dito. It also employs our model to obtain an appreciation of the startup delay penalties incured by slow start during handovers in typical mobile, real-time traffic scenarios.

Place, publisher, year, edition, pages
IEEE conference proceedings, 2011
Series
IEEE International Conference on Computer Communications and Networks
Keyword
Bit rate, Delay, IP networks, Internet, Mobile communication, Mobile handsets, Real time systems
National Category
Computer Sciences
Research subject
Computer Science
Identifiers
urn:nbn:se:kau:diva-10787 (URN)10.1109/ICCCN.2011.6005825 (DOI)000299260700072 ()978-1-4577-0637-0 (ISBN)
Conference
Flexibility in Broadband Wireless Access Network (FlexBWAN) Workshop, August 1-4, 2011, Maui, HI
Available from: 2012-02-08 Created: 2012-02-08 Last updated: 2018-01-12Bibliographically approved
6. On the Use of an Increased Initial Congestion Window to Improve mSCTP Handover Performance
Open this publication in new window or tab >>On the Use of an Increased Initial Congestion Window to Improve mSCTP Handover Performance
2012 (English)In: WAINA 2012: 26th International Conference on Advanced Information Networking and Applications Workshops / [ed] Leonard Barolli, Tomoya Enokido, Fatos Xhafa, Makoto Takizawa, IEEE Press, 2012, p. 1101-1106Conference paper, Published paper (Refereed)
Abstract [en]

With the wireless landscape being ratherheterogeneous, handover between different networktechnologies, so-called vertical handover, becomes keyto a continued success for wireless Internet access.Recently, an extension to the Stream Control Trans-mission Protocol (SCTP) – the Dynamic Address Re-configuration (DAR) extension – was standardized bythe IETF. This extension enables the use of SCTPfor vertical handover. Still, the way vertical handoverworks in SCTP with DAR makes it less suitable for real-time traffic. Particularly, it takes a significant amountof time for the traffic to ramp up to full speed on thehandover target path. In this paper, we study the ex-tent to which an increased initial congestion window onthe handover target path decreases the transfer delayspikes in real-time video traffic experienced during avertical handover. The impact on both standard andhigh-definition video traffic is considered. The resultsof our study suggest that an increased initial congestionwindow does indeed significantly decrease the spikes inthe video traffic. However, the results also indicate thatit does not resolve the problem altogether.

Place, publisher, year, edition, pages
IEEE Press, 2012
Keyword
SCTP; Dynamic Address Reconfiguration; Video; Mobility; Multihoming; Congestion Control; Handover
National Category
Computer Systems
Research subject
Computer Science
Identifiers
urn:nbn:se:kau:diva-13350 (URN)10.1109/WAINA.2012.111 (DOI)978-0-7695-4652-0 (ISBN)
Conference
WAINA 2012 - 26th IEEE International Conference on Advanced Information Networking and Applications Workshops, Fukuoka, Japan, March 26-29
Projects
SCTP Smartswitch
Note

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Available from: 2012-05-22 Created: 2012-05-22 Last updated: 2017-12-06Bibliographically approved
7. Implications of using a Large Initial Congestion Window to Improve mSCTP Handover Delay
Open this publication in new window or tab >>Implications of using a Large Initial Congestion Window to Improve mSCTP Handover Delay
2012 (English)In: MOBILITY 2012 : The Second International Conference on Mobile Services, Resources, and Users / [ed] Josef Noll, University of Oslo & Movation, Norway, Alessandro Bazzi, CNR - IEIIT, Italy, IARIA , 2012, , p. 6p. 116-121Conference paper, Published paper (Refereed)
Abstract [en]

The currently rather heterogeneous wireless landscape makes handover between different network technologies, so-called vertical handover, a key to a continued success for wireless Internet access. Recently, an extension to the Stream Control Transmission Protocol (SCTP) – the Dynamic Address Reconfiguration (DAR) extension – was standardized by IETF. This extension enables the use of SCTP for vertical handover. Still, the way vertical handover works in SCTP with DAR makes it less suitable for real-time traffic. Particularly, it takes a significant amount of time for the traffic to ramp up to full speed on the handover target path. In this paper, we study the implications of an increased initial congestion window for real-time traffic on the handover target path when competing traffic is present. The results clearly show that an increased initial congestion window could significantly reduce the transfer delay for real-time traffic, provided the fair share of the available capacity on the handover target path is sufficiently higher than the send rate required by the real-time flow. Additionally, we notice that this performance gain comes without penalizing the competing traffic.

Place, publisher, year, edition, pages
IARIA, 2012. p. 6
Keyword
SCTP, dynamic address reconfiguration, video, mobility, handover, congestion control, slow start
National Category
Telecommunications
Research subject
Computer Science
Identifiers
urn:nbn:se:kau:diva-26493 (URN)978-1-61208-229-5 (ISBN)
Conference
The Second International Conference on Mobile Services, Resources, and Users (MOBILITY, Venice, Italy from October 21, 2012 to October 26, 2012
Projects
SCTP SmartSwitch - Smart Session Management for Multihomed SCTP
Funder
Vinnova
Available from: 2013-02-25 Created: 2013-02-25 Last updated: 2017-12-06Bibliographically approved
8. Handover in the Wild: The Feasibility of Vertical Handover in Commodity Smartphones
Open this publication in new window or tab >>Handover in the Wild: The Feasibility of Vertical Handover in Commodity Smartphones
Show others...
2013 (English)In: Proceedings of the IEEE International Conference on Communications (ICC), IEEE, 2013, p. 6401-6406Conference paper, Published paper (Refereed)
Abstract [en]

Today commodity mobile devices are frequently equipped with two wireless access technologies,WiFi and 3G/4G. To enable continuous connectivity it is vital that these terminals provide for vertical handover between different technologies. Particularly, they should provide a vertical handover that complies with the timeliness requirements of soft real-time applications. Considering aspects such as cost and ease-of-deployment, ap- plication neutrality, and, not least, the emergence of transport protocols that support multi-homing such as mobile SCTP and multi-path TCP, we think it would be beneficial to handle vertical handover in the transport layer of the mobile terminal. This paper demonstrates through several real-world experiments, the feasibility of using a lightweight vertical handover scheme in smart mobile terminals for live video streaming. The vertical handover criteria is based on the received signal strength. Our experiments suggest that the scheme indeed provides for seamless vertical handover at walking speed – our target scenario. However, the experiments also suggest that the scheme gives significant reductions in handover time, as compared to mobile SCTP without improvements, at higher speeds.

Place, publisher, year, edition, pages
IEEE, 2013
Series
IEEE International Conference on Communications, ISSN 1550-3607
Keyword
sctp, dar, vertical handover
National Category
Telecommunications
Research subject
Computer Science
Identifiers
urn:nbn:se:kau:diva-33907 (URN)10.1109/ICC.2013.6655635 (DOI)000349673807056 ()978-1-4673-3122-7 (ISBN)
Conference
IEEE International Conference on Communications (ICC) 2013, Budapest, Hungary, June 9-13, 2013
Funder
VINNOVA
Available from: 2014-10-01 Created: 2014-10-01 Last updated: 2017-12-06Bibliographically approved

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