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  • 1.
    Abbas, Muhammad Tahir
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för matematik och datavetenskap (from 2013).
    Eklund, Johan
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för matematik och datavetenskap (from 2013).
    Grinnemo, Karl-Johan
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för matematik och datavetenskap (from 2013).
    Brunström, Anna
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för matematik och datavetenskap (from 2013).
    Impact of Tunable Parameters in NB-IoT Stack onthe Energy Consumption2019Ingår i: Proceedings of Fifteenth Swedish National Computer Networking Workshop (SNCNW), 2019Konferensbidrag (Refereegranskat)
    Abstract [en]

    This paper studies the impact of tunable parametersin the NB-IoT stack on the energy consumption of a user equipment(UE), e.g., a wireless sensor. NB-IoT is designed to enablemassive machine-type communications for UE while providing abattery lifetime of up to 10 years. To save battery power, most oftime the UE is in dormant state and unreachable. Still, duringthe CONNECTED and IDLE state, correct tuning of criticalparameters, like Discontinuous reception (DRX), and extendedDiscontinuous reception (eDRX), respectively, are essential to savebattery power. Moreover, the DRX and eDRX actions relate tovarious parameters which are needed to be tuned in order toachieve a required UE battery lifetime. The objective of thispaper is to observe the influence of an appropriate tuning ofthese parameters to reduce the risk of an early battery drainage

  • 2.
    Eklund, Johan
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Evaluation of Emulab as Experimental Platform by comparing TCP and SCTP2004Övrigt (Övrig (populärvetenskap, debatt, mm))
    Abstract [en]

    To be able to evaluate new protocols it is important to have access to good experimental environments. Several experiments are needed to verify different aspects of protocol performance as well as robustness under various network conditions. Emulab is a new public experimental platform which is available for remote users. The ambition is that Emulab should offer the user the possibility to perform both simulation and emulation of a network. In addition, Emulab offers access to an experimental live network. This thesis presents a study where a series of tests are performed on the Emulab platform and also gives an introduction to SCTP. The first objective of the thesis is to obtain practical experience and to evaluate the usability of Emulab and the second objective is to compare the throughput between the transport protocols TCP and SCTP. The experiences from using Emulab are very positive. The results show that Emulab is a reliable and robust platform with high availability. The throughput comparison did not reveal significant differences between SCTP and TCP under moderate traffic load. Further tests and analyses are necessary to obtain a clear view of the situation in a heavily loaded network

  • 3.
    Eklund, Johan
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för matematik och datavetenskap (from 2013). Karlstad University.
    Latency Reduction for Soft Real-Time Traffic using SCTP Multihoming2016Doktorsavhandling, sammanläggning (Övrigt vetenskapligt)
    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.

  • 4.
    Eklund, Johan
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    On Switchover Performance in Multihomed SCTP2010Licentiatavhandling, sammanläggning (Övrigt vetenskapligt)
    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.

  • 5.
    Eklund, Johan
    et al.
    Karlstads universitet, Institutionen för informationsteknologi.
    Brunstrom, Anna
    Karlstads universitet, Institutionen för informationsteknologi.
    Performance of Network Redundancy Mechanisms in SCTP2005Rapport (Övrigt vetenskapligt)
    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.

  • 6.
    Eklund, Johan
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Brunstrom, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Grinnemo, Karl-Johan
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Improving mSCTP-based Vertical Handovers by Increasing the Initial Congestion Window2011Ingår i: / [ed] Johan Eklund,Karl-Johan Grinnemo, Anna Brunstrom, 2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    Wireless networks play an increasingly important role in our daily lives. However, the wireless landscape comprises serveralnetwork technologies, and which technology to use is often context dependent and varies over time: In urban areas, WiFi viaa WiFi hotspot might be the preferred access technology, while in rural areas 3G, HSPA or some other 3GPP technologymight be the only viable alternative. To this end, a large number of vertical handover solutions, ranging from link-level toapplication-level solutions, has been proposed in the past several years.We believe that the Stream Control Transmission Protocol and its extension for Dynamic Address Reconfiguration (mSCTP)make up an attractive vertical handover solution, especially in cases where there are little or no economic incentives to modify orupgrade the existing network infrastructure. Currently, we are implementing an mSCTP-based mobility management frameworkfor Android smartphones and tablets, and as part of that work we are considering ways of mitigating the effects of a handoveron ongoing transport sessions.A mobile terminal with several network interfaces may traverse different types of networks (WLAN, UMTS, HSPA).A seamless handover between these networks may be achieved by the transport protocol, Stream Control TransmissionProtocol(SCTP), with its multihoming facility (mSCTP), in conjunction with a mobility manager monitoring the availablenetwork interfaces. SCTP, a reliable transport protocol, closely related to TCP, encompasses slow-start in the beginning of asession. This slow-start phase is also activated to probe for network capacity on the target path after a handover, which couldresult in unncessarily reduced throughput in case of spare capacity in the network. The throughput degradation in could becrucial for an ongoing real time session, like video conferencing. In this study we have conducted experiments on the benefitof increasing the initial congestion window to reduce the negative impact of the slow start phase. We have by experimentsquantified the performance gain from an increasd initial window, and have seen that there a reduction in maximum transfertime for a message of about 50 % in scenarios with real-time video, compared to the default initial congestion window. Theimprovement is most prominent in sessions with high transfer delays. One easy, and thus very attractive, way to improveon the handover performance is to increase the initial congestion window on the handover target path. Although a seeminglycontroversal proposition, one should bear in mind that researchers at Google and other cloud computing companies are currentlystrongly promoting a drastic increase of TCP’s initial congestion window within IETF.

  • 7.
    Eklund, Johan
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Brunström, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Impact of SACK delay and link delay on Failover performance in SCTP2006Konferensbidrag (Refereegranskat)
    Abstract [en]

    The Stream Control Transmission Protocol (SCTP) was developed

    to support the transfer of telephony signaling over

    IP networks. One of the ambitions when designing SCTP

    was to offer a robust transfer of traffic between hosts. For

    this reason SCTP was designed to support multihoming,

    which gives 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.

    Consequently, the time between occurrence of a break on

    the primary path until the traffic is run smoothly on one of

    the alternate paths is important. This paper presents experimental

    results concerning SCTP failover performance. The

    focus in this paper is to evaluate the impact of the SACK

    delay and link delay on the failover time as well as on the

    maximum transfer time for a single message, which complements

    earlier studies in this area. The results show a

    significant performance impact of the SACK delay as well

    as of the link delay. This suggests that the SACK delay

    is an important parameter to tune to enhance application

    transparency in failure situations

  • 8.
    Eklund, Johan
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Brunström, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Performance of Network Redundancy Mechanisms in SCTP2005Rapport (Refereegranskat)
    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 an experiment 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 experiment is 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 experiment is performed in a network without concurrent traffic and in conclusion the results from the experiment 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.

  • 9.
    Eklund, Johan
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Brunström, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Grinnemo, Karl-Johan
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Cheimonidis, Georgios
    Ismailov, Yuri
    Delay Penalty during SCTP Handover2011Konferensbidrag (Refereegranskat)
    Abstract [en]

    The rapidly growing interest in untethered Internet connections such as WLAN and 3G/4G mobile connections,calls for intelligent session management, not least in terms of handovers. As part of an effort to develop a SCTP-based session management framework, we are studying ways of improving the SCTP handover delay forreal-time traffic by optimizing the startup delay on the handover-target path. We have developed a theoretical model that predicts the transfer times of SCTP messages during the startup on a new path. This paper validates our model. It shows that the model can be used to predict message transfer times in variable bitrate flows. The paper further employs our model to study the startup delay penalty during handover for the spectrum of network conditions considered relevant for real-time traffic over mobile connections.

  • 10.
    Eklund, Johan
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Brunström, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Grinnemo, Karl-Johan
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Cheimonidis, Georgios
    Ismailov, Yuri
    Impact of Slow Start on SCTP Handover Performance2011Ingår i: Proceedings of 20th International Conference on Computer Communications and Networks: ICCCN2011, IEEE conference proceedings, 2011Konferensbidrag (Refereegranskat)
    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.

  • 11.
    Eklund, Johan
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Grinnemo, Karl-Johan
    School of Information and Communication Technology, KTH Royal Institute of Technology.
    Baucke, Stephan
    Ericsson Research, Germany.
    Brunstrom, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Tuning SCTP Failover for Carrier Grade Telephony Signaling2010Ingår i: Computer Networks, ISSN 1389-1286, E-ISSN 1872-7069, Vol. 54, nr 1, s. 133-149Artikel i tidskrift (Refereegranskat)
    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.

  • 12.
    Eklund, Johan
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för matematik och datavetenskap (from 2013).
    Grinnemo, Karl-Johan
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap. Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för matematik och datavetenskap (from 2013).
    Brunstrom, Anna
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för matematik och datavetenskap (from 2013).
    Efficient Scheduling to Reduce Latency for Signaling Traffic using CMT-SCTP2016Ingår i: 27th Annual IEEE International Symposium on Personal, Indoor and Mobile Radio Communications (PIMRC), September 4-7, Valencia, Spain, IEEE, 2016, s. 2127-2132Konferensbidrag (Refereegranskat)
    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. 

  • 13.
    Eklund, Johan
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Grinnemo, Karl-Johan
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Brunstrom, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Implications of using a Large Initial Congestion Window to Improve mSCTP Handover Delay2012Ingår i: 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, , s. 6s. 116-121Konferensbidrag (Refereegranskat)
    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.

  • 14.
    Eklund, Johan
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Grinnemo, Karl-Johan
    Tieto Enator AB, Karlstad, Sweden.
    Brunstrom, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    On the Relation Between SACK Delay and SCTP Failover Performance for Different Traffic Distributions2008Ingår i: Proceedings on the Fifth International Conference on Broadband Communications, Networks and Systems, IEEE , 2008, s. 577-584Konferensbidrag (Refereegranskat)
    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

  • 15.
    Eklund, Johan
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Grinnemo, Karl-Johan
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Brunstrom, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    On the Use of an Increased Initial Congestion Window to Improve mSCTP Handover Performance2012Ingår i: WAINA 2012: 26th International Conference on Advanced Information Networking and Applications Workshops / [ed] Leonard Barolli, Tomoya Enokido, Fatos Xhafa, Makoto Takizawa, IEEE Press, 2012, s. 1101-1106Konferensbidrag (Refereegranskat)
    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.

  • 16.
    Eklund, Johan
    et al.
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Grinnemo, Karl-Johan
    School of Information and Communication Technology, KTH Royal Institute of Technology.
    Brunstrom, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Theoretical Analysis of an Ideal Startup Scheme in Multihomed SCTP2010Ingår i: 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, s. 155-166Konferensbidrag (Refereegranskat)
    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

  • 17.
    Eklund, Johan
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för matematik och datavetenskap.
    Grinnemo, Karl-Johan
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för matematik och datavetenskap.
    Brunström, Anna
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för matematik och datavetenskap.
    On the Impact of Data Scheduling to Reduce Latency for Telephony Signaling Traffic using CMT-SCTP2015Ingår i: The 11th Swedish National Computer Networking Workshop (SNCNW), Karlstad, Sweden, May 28-29, 2015., 2015Konferensbidrag (Övrigt vetenskapligt)
    Abstract [en]

    SCTP is a transport protocol targeted for telephony signaling traffic. Although SCTP from its inception supported multihoming, it has until now not supported concurrent mul- tipath transfer. However, this is about to change: Currently a standard for concurrent multipath transfer is underway. Since it is unclear whether concurrent multipath transfer could reduce transmission latency, this paper evaluates two algorithms for scheduling signaling traffic for transmission. We find that the mechanisms may provide good performance and to some extent enables for service differentiation. Still, the results indicate that unpredictable traffic require dynamic scheduling.

  • 18.
    Eklund, Johan
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för matematik och datavetenskap.
    Grinnemo, Karl-Johan
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Brunström, Anna
    Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Avdelningen för datavetenskap.
    Stream-aware Scheduling to Improve Latency for Signaling Traffic using CMT-SCTP2016Konferensbidrag (Refereegranskat)
    Abstract [en]

    To mitigate delay spikes during transmission ofbursty signaling traffic, concurrent multipath transmission(CMT) over several paths in parallel could be an option. Still,unordered delivery is a well known problem when transmittingover asymmetric network paths, leading to extra delay due toHead-of-Line Blocking (HoLB). The Stream Control TransmissionProtocol (SCTP) is designed as a carrier for signaling trafficover IP to reduce the impact of HoLB. SCTP has support fortransmission of separate flows, called SCTP streams. SCTP iscurrently being extended with support for CMT (CMT-SCTP). Inthis paper, we address sender scheduling to optimize latency forsignaling traffic over CMT-SCTP. We present dynamic streamaware(DS) scheduling, which utilizes the SCTP stream concept,and continuously considers the current network status as well asthe data load to make scheduling decisions. We implement a DSScheduler and compare it against a dynamic path (DP) schedulerthat does not consider streams. Our investigation shows that DSscheduling could significantly reduce latency compared to a DPscheduler.

  • 19.
    Eklund, Johan
    et al.
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för matematik och datavetenskap (from 2013). Karlstads universitet, Fakulteten för ekonomi, kommunikation och IT, Centrum för HumanIT.
    Grinnemo, Karl-Johan
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för matematik och datavetenskap (from 2013).
    Brunström, Anna
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för matematik och datavetenskap (from 2013).
    Using multiple paths in SCTP to reduce latency for signaling traffic2018Ingår i: Computer Communications, ISSN 0140-3664, E-ISSN 1873-703X, Vol. 129, s. 184-196Artikel i tidskrift (Refereegranskat)
    Abstract [en]

    The increase in traffic volumes as well as the heterogeneity in network infrastructure in the upcoming 5G cellular networks will lead to a dramatic increase in volumes of control traffic, i.e., signaling traffic, in the networks. Moreover, the increasing number of low-power devices with an on-off behavior to save energy will generate extra control traffic. These increased traffic volumes for signaling traffic, often generated as bursts of messages, will challenge the signaling application timing requirements on transmission. One of the major transport protocols deployed for signaling traffic in cellular networks is the Stream Control Transmission Protocol (SCTP), with support for multiple paths as well as for independent data flows. This paper evaluates transmission over several paths in SCTP to keep the latency low despite increasing traffic volumes. We explore different transmission strategies and find that concurrent multipath transfer over several paths will significantly reduce latency for transmission over network paths with the same or similar delay. Still, over heterogeneous paths, careful, continuous sender scheduling is crucial to keep latency low. To this end, we design and evaluate a sender scheduler that considers path characteristics as well as queuing status and data flows of different priority to make scheduling decisions. Our results indicate that by careful dynamic sender scheduling, concurrent multipath transfer could lead to reduced latency for signaling traffic irrespective of path or traffic characteristics.

  • 20.
    Söderman, Pehr
    et al.
    KTH Royal Institute of Technology.
    Eklund, Johan
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för matematik och datavetenskap.
    Grinnemo, Karl-Johan
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för matematik och datavetenskap.
    Hidell, Marcus
    KTH.
    Brunstrom, Anna
    Karlstads universitet, Fakulteten för hälsa, natur- och teknikvetenskap (from 2013), Institutionen för matematik och datavetenskap.
    Handover in the Wild: The Feasibility of Vertical Handover in Commodity Smartphones2013Ingår i: Proceedings of the IEEE International Conference on Communications (ICC), IEEE, 2013, s. 6401-6406Konferensbidrag (Refereegranskat)
    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.

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