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Improving the Timeliness of SCTP Message Transfers
Karlstad University, Faculty of Economic Sciences, Communication and IT, Department of Computer Science. (Datavetenskap)ORCID iD: 0000-0002-8731-2482
2008 (English)Licentiate thesis, comprehensive summary (Other scientific)
Abstract [en]

Due to the cheap and flexible framework that the underlying IP-technology of the internet provides, IP-networks are becoming popular in more and more contexts. For instance, telecommunication operators have started to replace the fixed legacy telephony networks with IP-networks. To support a smooth transition towards IP-networks, the Stream Control Transmission Protocol (SCTP) was standardized. SCTP is used to carry telephony signaling traffic, and solves a number of problems that would have followed from using the Transmission Control Protocol (TCP) in this context. However, the design of SCTP is still heavily influenced by TCP. In fact, many protocol mechansisms in SCTP are directly inherited from TCP. Unfortunately, many of these mechanisms are not adapted to the kind of traffic that SCTP is intended to transport: time critical message-based traffic, e.g. telephony signaling.In this thesis we examine, and adapt some of SCTP's mechanisms to more efficiently transport time critical message-based traffic. More specifically, we adapt SCTP's loss recovery and message bundling for timely message transfers. First, we propose and experimentally evaluate two loss recovery mechanisms: a packet-based Early Retransmit algorithm, and a modified retransmission timeout management algorithm. We show that these enhancements can reduce loss recovery times with at least 30-50%, in some scenarios. In addition, we adapt the message bundling of SCTP to better support timely message delivery. The proposed bundling algorithm can in some situations reduce the transfer time of a message with up to 70%.In addition to these proposals we have also indentified and reported mistakes in some of the most popular SCTP implementations. Furthermore, we have continously developed the network emulation software KauNet to support our experimental evaluations.

Place, publisher, year, edition, pages
Karlstad: Karlstad University , 2008. , p. 12
Series
Karlstad University Studies, ISSN 1403-8099 ; 2008:43
Keywords [en]
SCTP, transport protocols, network emulation, loss recovery, Nagle algorithm
National Category
Computer Sciences
Research subject
Materials Engineering
Identifiers
URN: urn:nbn:se:kau:diva-2861ISBN: 978-91-7063-202-0 (print)OAI: oai:DiVA.org:kau-2861DiVA, id: diva2:54431
Presentation
2008-11-07, Fryxellsalen, 1B 306, Karlstads universitet, Karlstad, 10:15 (English)
Supervisors
Available from: 2008-11-25 Created: 2008-10-16 Last updated: 2018-01-12Bibliographically approved
List of papers
1. Loss Recovery in Short TCP/SCTP Flows
Open this publication in new window or tab >>Loss Recovery in Short TCP/SCTP Flows
2006 (English)Report (Other academic)
Abstract [en]

The Transmission Control Protocol (TCP) has been the dominant transport protocol within IP-based networks for many years, mainly due to the reliability it provide to its users and the congestion control it employs. However, as the amount of signaling traffic within IP-based networks have increased significantly in recent years, it has become clear that TCP is not suited for this kind of traffic. In order to meet the requirements of signaling traffic the Stream Control Transmission Protocol (SCTP) was developed by the Internet Engineering Task Force (IETF). SCTP is heavily influenced by TCP and is therefore similar to TCP in many ways. One example is the SCTP loss recovery and congestion control mechanisms which are almost identical to those of TCP. The primary purpose of this work is to study the performance and behavior of the TCP/SCTP loss recovery mechanisms for short flows. Using a simple client/server model, we evaluate the performance of these mechanism over a wide range of bandwidths, link delays and packet loss patterns. The experiments evaluate one TCP implementation and two SCTP implementations, and were conducted using network emulation. The experimental results show that there exist strong dependencies between the position of packet loss and the actual transmission time of the corresponding flow. In addition to these dependencies, we also found a number of implementation mistakes in the examined protocol implementations.

Place, publisher, year, edition, pages
Karlstad: Karlstads universitet, 2006. p. 59
Series
Karlstad University Studies, ISSN 1403-8099 ; 2006:71
Keywords
tcp, sctp, loss recovery, emulation, performance evaluation
National Category
Computer Systems
Identifiers
urn:nbn:se:kau:diva-725 (URN)91-7063-101-8 (ISBN)
Available from: 2007-04-13 Created: 2007-04-13 Last updated: 2018-08-14
2. Enhancing SCTP Loss Recovery: An Experimental Evaluation of Early Retransmit
Open this publication in new window or tab >>Enhancing SCTP Loss Recovery: An Experimental Evaluation of Early Retransmit
2008 (English)In: Computer Communications, ISSN 0140-3664, E-ISSN 1873-703X, Vol. 31, no 16, p. 3778-3788Article in journal (Refereed) Published
Abstract [en]

To reduce cost and provide more flexible services, telecommunication operators are currently replacing traditional circuit-switched telephony networks with packet-switched IP networks. To support the stringent requirements of telephony signaling (SS7), the SIGTRAN working group of the IETF specified the transport protocol SCTP. SCTP was developed to overcome a number of problems that follow from using TCP for signaling transport. However, the design of SCTP was to a great extent still based on TCP, and some problems related to signaling transport were inherited. For example, the loss recovery mechanisms in SCTP are almost identical to those of TCP. This is a problem as signaling traffic has stringent requirements on timely message delivery. TCP was not designed to meet stringent requirements on timely message delivery, and therefore the loss recovery was not optimized for it. To optimize SCTP’s loss recovery for signaling traffic, we consider the loss recovery enhancement early retransmit. To make early retransmit even better suited for signaling traffic we propose a packet-based version, which was also recently included in the early retransmit specification. By experimentally evaluating this algorithm, we show that the packet-based early retransmit algorithm, in some cases, can reduce SCTP’s loss recovery time by 62%.

Place, publisher, year, edition, pages
Amsterdam: Elsevier, 2008
National Category
Computer Systems
Research subject
Computer Science
Identifiers
urn:nbn:se:kau:diva-2857 (URN)10.1016/j.comcom.2008.04.024 (DOI)
Available from: 2008-10-16 Created: 2008-10-16 Last updated: 2018-06-04Bibliographically approved
3. Improved Loss Detection for Signaling Traffic in SCTP
Open this publication in new window or tab >>Improved Loss Detection for Signaling Traffic in SCTP
2008 (English)In: IEEE International Conference on Communications (ICC 08), IEEE , 2008, p. 5886-5891Conference paper, Published paper (Refereed)
Abstract [en]

The Stream Control Transmission Protocol (SCTP) was designed by the IETF as a viable solution for transportation of signaling traffic within IP-based networks. Signaling traffic is different from ordinary TCP bulk traffic in many ways. One example is that the requirement of timely delivery usually is much stricter. However, the management of the SCTP retransmission timer is not optimally designed considering this requirement. Basically, the management algorithm, unnecessarily, extends the time needed for loss detection. This paper presents a new management algorithm that is able to maintain a correct state of the retransmission timer, which eliminates this particular problem. In addition, the paper also compares the performance of the two management algorithms in an emulated signaling environment, using the lksctp implementation of SCTP. The results show that the proposed algorithm is able to provide significant reductions in loss recovery time. In some cases, the time needed to recover from packet loss is reduced with as much as 43%.

Place, publisher, year, edition, pages
IEEE, 2008
National Category
Computer Systems
Research subject
Computer Science
Identifiers
urn:nbn:se:kau:diva-2859 (URN)10.1109/ICC.2008.1100 (DOI)978-1-4244-2075-9 (ISBN)
Available from: 2008-10-16 Created: 2008-10-16 Last updated: 2018-06-04Bibliographically approved
4. SCTP: Designed for Timely Message Delivery?
Open this publication in new window or tab >>SCTP: Designed for Timely Message Delivery?
2011 (English)In: Telecommunications Systems, ISSN 1018-4864, E-ISSN 1572-9451, Vol. 47, no 3-4, p. 323-336Article in journal (Refereed) Published
Abstract [en]

To reduce cost and provide more flexible services, telecommunication operators are currently replacing traditional telephony networks with IP-networks. To support the requirements of telephony signaling in IP-networks, SCTP was standardized. SCTP solves a number of problems that follows from using TCP for telephony signaling transport. However, the design of SCTP is still largely based on TCP, and most of SCTP's data transmission mechanisms are inherited from TCP. Signaling traffic has stricter requirements of timely delivery than TCP bulk traffic. However, such requirements are not supported optimally by the inherited TCP mechanisms. We therefore argue that SCTP is not fully designed for timely message delivery. In this article we present and evaluate two loss recovery adaptations that enhance the timeliness of SCTP: Early Retransmit and a modified RTO management algorithm. In addition, we evaluate an adapted Nagle-like algorithm. The results from our evaluation show a significant reduction of message delivery times. In many of the experiments, delivery times were reduced with at least 30-50%. Furthermore, in some situations, message delivery times were reduced with up to 70%, using the modified Nagle algorithm.

Keywords
SCTP, TCP, loss recovery, nagle, network emulation
National Category
Computer Systems
Research subject
Computer Science
Identifiers
urn:nbn:se:kau:diva-2860 (URN)10.1007/s11235-010-9321-3 (DOI)000291242600012 ()
Available from: 2008-11-25 Created: 2008-10-16 Last updated: 2018-06-04Bibliographically approved

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