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On Switchover Performance in Multihomed SCTP
Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science.ORCID iD: 0000-0002-6723-881X
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. , p. 127
Series
Karlstad University Studies, ISSN 1403-8099 ; 2010:12
Keywords [en]
Computer Networking, Transport Protocols, Multihoming, Performance Evaluation, Signaling Traffic
National Category
Computer Sciences
Research subject
Computer Science
Identifiers
URN: urn:nbn:se:kau:diva-5501ISBN: 978-91-7063-298-3  (print)OAI: oai:DiVA.org:kau-5501DiVA, id: diva2:305835
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: 2018-01-12Bibliographically approved
List of papers
1. Performance of Network Redundancy Mechanisms in SCTP
Open this publication in new window or tab >>Performance of Network Redundancy Mechanisms in SCTP
2005 (English)Report (Other academic)
Abstract [en]

One of the ambitions when designing the Stream Control Transmission Protocol was to offer a robust transfer of traffic between hosts. For this reason SCTP was designed to support multihoming, which presumes the possibility to set up several paths between the same hosts in the same session. If the primary path between a source machine and a destination machine breaks down, the traffic may still be sent to the destination, by utilizing one of the alternate paths. The failover that occurs when changing path is to be transparent to the application.

This paper describes the results from experiments concerning SCTP failover performance, which means the time between occurrence of a break on the primary path until the traffic is run smoothly on the alternate path. The experiments are performed mainly to verify the Linux Kernel implementation of SCTP (LK-SCTP) and is run on the Emulab platform. The results will serve as a basis for further experiments.

The experiments are performed in a network without concurrent traffic and in conclusion the results from the experiments correspond well to the values found in other studies and they are close to the theoretical best values. As expected the parameter Path.Max.Retrans has a great impact on the failover time. One observation is that the failover time and the max transfer time for a message are dependent upon the status in the network when the break of the primary path occurs.

Series
Karlstad University Studies, ISSN 1403-8099 ; 2005:48
Keywords
SCTP, failover, performance measurement
National Category
Computer Systems
Identifiers
urn:nbn:se:kau:diva-2402 (URN)91-7063-019-4 (ISBN)
Available from: 2010-06-01 Created: 2010-06-01 Last updated: 2018-06-04Bibliographically approved
2. 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
Keywords
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: 2018-06-04Bibliographically approved
3. 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
Keywords
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: 2018-06-04Bibliographically 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
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