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Tuning SCTP Failover for Carrier Grade Telephony Signaling
Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. (Datavetenskap)
School of Information and Communication Technology, KTH Royal Institute of Technology. (Datavetenskap)ORCID iD: 0000-0003-4147-9487
Ericsson Research, Germany.
Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. (Datavetenskap)
2010 (English)In: Computer Networks, ISSN 1389-1286, E-ISSN 1872-7069, Vol. 54, no 1, 133-149 p.Article 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. Vol. 54, no 1, 133-149 p.
Keyword [en]
SCTP, Reliable transport protocol, Robustness, Failover performance
National Category
Computer Systems
Research subject
Computer Science
Identifiers
URN: urn:nbn:se:kau:diva-5692DOI: 10.1016/j.comnet.2009.08.016OAI: oai:DiVA.org:kau-5692DiVA: diva2:321514
Available from: 2010-06-01 Created: 2010-06-01 Last updated: 2016-05-18Bibliographically approved
In thesis
1. On Switchover Performance in Multihomed SCTP
Open this publication in new window or tab >>On Switchover Performance in Multihomed SCTP
2010 (English)Licentiate thesis, comprehensive summary (Other academic)
Abstract [en]

The emergence of real-time applications, like Voice over IP and video conferencing, in IP networks implies a challenge to the underlying infrastructure. Several real-time applications have requirements on timeliness as well as on reliability and are accompanied by signaling applications to set up, tear down and control the media sessions. Since neither of the traditional transport protocols responsible for end-to-end transfer of messages was found suitable for signaling traffic, the Stream Control Transmission Protocol (SCTP) was standardized. The focus for the protocol was initially on telephony signaling applications, but it was later widened to serve as a general purpose transport protocol. One major new feature to enhance robustness in SCTP is multihoming, which enables for more than one path within the same association.

In this thesis we evaluate some of the mechanisms affecting transmission performance in case of a switchover between paths in a multihomed SCTP session. The major part of the evaluation concerns a failure situation, where the current path is broken. In case of failure, the endpoint does not get an explicit notification, but has to react upon missing acknowledgements. The challenge is to distinguish path failure from temporary congestion to decide  when to switch to an alternate path. A too fast switchover may be spurious, which could reduce transmission performance, while a too late switchover also results in reduced transmission performance. This implies a tradeoff which involves several protocol as well as network parameters and we elaborate among these to give a coherent view of the parameters and their interaction. Further, we present a recommendation on how to tune the parameters to meet  telephony signaling requirements, still without violating fairness to other traffic.

We also consider another angle of switchover performance, the startup on the alternate path. Since the available capacity is usually unknown to the sender, the transmission on a new path is started at a low rate and then increased as acknowledgements of successful transmissions return. In case of switchover in the middle of a media session the startup phase after a switchover could cause problems to the application. In multihomed SCTP the availability of the alternate path makes it feasible for the end-host to estimate the available capacity on the alternate path prior to the switchover. Thus, it would be possible to implement a more efficient startup scheme. In this thesis we combine different switchover scenarios with relevant traffic. For these combinations, we analytically evaluate and quantify the potential performance gain from utilizing an ideal startup mechanism as compared to the traditional startup procedure.

Place, publisher, year, edition, pages
Karlstad: Karlstad University, 2010. 127 p.
Series
Karlstad University Studies, ISSN 1403-8099 ; 2010:12
Keyword
Computer Networking, Transport Protocols, Multihoming, Performance Evaluation, Signaling Traffic
National Category
Computer Science
Research subject
Computer Science
Identifiers
urn:nbn:se:kau:diva-5501 (URN)978-91-7063-298-3  (ISBN)
Presentation
2010-05-19, Fryxellsalen, 1B 306, Karlstads universitet, Karlstad, 10:00 (Swedish)
Opponent
Supervisors
Available from: 2010-06-03 Created: 2010-03-25 Last updated: 2011-10-24Bibliographically approved
2. Latency Reduction for Soft Real-Time Traffic using SCTP Multihoming
Open this publication in new window or tab >>Latency Reduction for Soft Real-Time Traffic using SCTP Multihoming
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. 34 p.
Series
Karlstad University Studies, ISSN 1403-8099 ; 2016:14
Keyword
transport protocol, SCTP, multihoming, latency, performance evaluation, failover, concurrent multipath transfer, scheduling, mobility, handover
National Category
Computer Science
Research subject
Computer Science
Identifiers
urn:nbn:se:kau:diva-40713 (URN)978-91-7063-693-6 (ISBN)
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: 2017-03-07Bibliographically approved

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Eklund, JohanGrinnemo, Karl-JohanBrunstrom, Anna

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