Duisburg, Essen, Univ. Diss., 2005. / Computerdatei im Fernzugriff.

SCTP (Steam Control Transmission Protocol)是由IETF[2]提出在傳輸層的新機制。SCTP像TCP一樣提供擁塞控制機制(congestion control mechanism)。此外，SCTP提供Multi-Homing和Multi-Streaming兩個TCP所缺乏的重要機制。然而，SCTP和TCP一樣無法分辨當快速重傳機制(Fast-Rtx)或是Timeout機制啟動時，packet-loss發生的真正原因，如瞬間的通道錯誤或因網路擁塞引起的封包拋棄。於此，SCTP會不正確地啟動擁塞控制機制來防止網路擁塞狀況的持續惡化。 本篇論文目的在於改善SCTP在無線網路所遭遇效能低落的問題。我們提出三種解決問題的機制，分別是SCTP-EnhancedProbing、SCTP-Duplicate 及SCTP-Changeover。SCTP-EnhancedProbing機制是一種點對點的方法，用以判斷packet-loss發生的真正原因。SCTP-Duplicate機制則藉由multi-homing機制來幫助提升SCTP-EnhancedProbing機制的效能。SCTP-Changeover機制則是一個必要的方法來補足SCTP-Duplicate機制所引發的問題，以提供良好的改善方案。最後，我們將利用網路模擬器NS-2 (Network Simulator ver. 2)來驗證並評估我們所提出三種方法的效能。 / SCTP (Stream Control Transmission Protocol) is a new proposed mechanism by IETF [2] at the transport layer. SCTP has similar congestion control mechanism as that in TCP, and embeds multi-homing and multi-streaming mechanisms that are not offered by TCP. However, SCTP can’t identify exactly whether the cause of packet-loss is from transient channel error or congestion error as fast-transmission or timeout is triggered. SCTP will thus invoke congestion control mechanism incorrectly. The objective of the thesis is to improve the performance of SCTP which suffers performance degradation in a wireless network. We propose SCTP-EnhancedProbing, SCTP-Duplicate and SCTP-Changeover three mechanisms for this end. SCTP-EnhancedProbing is an end-to-end mechanism used to identify the cause of packet-loss. SCTP-Duplicate employs the multi-homing feature to enhance SCTP-EnhancedProbing performance. SCTP-Changeover is a necessary complement to SCTP-Duplicate mechanism. Moreover, the proposed SCTP-Changeover is an effective solution to the changeover problem in SCTP. At last, we verify and evaluate the performances of the three proposed mechanisms using Network Simulator 2 (NS-2), respectively.

Duisburg, Essen, University Diss., 2005.

Essen, Universiẗat Diss., 2005--Duisburg.

Duisburg, Essen, Univ. Diss., 2005

To support the transmission of real-time multimedia stream, Stream Control Transmission Protocol (SCTP) developed by IETF is considered to be more efficient because of its high-degree expandability and compatibility. Today we can observe that instead of using SCTP may become the transmission protocol of next-generation IP network. In this Thesis, we propose a mechanism to upgrade TCP and UDP, the multi-home feature of SCTP to ensure that multiple paths can exist between two SCTP ends. Not only can the primary path continue to function, but the secondary paths covey part of data packets once the network congestion occurs. Considering the dynamic change of our Internet, the proposed mechanism can enhance the effectiveness of SCTP data transmission, and increase overall network utilization. Cutting user data into chunks in SCTP, we can analyze the transmission performance of individual path by measuring the transmission delay from the sender to the receiving end. By modifying the simulator of NS-2, we set up different topologies in the experiment to analyze the performance of our mechanism. We compare the modified SCTP with the original SCTP to highlight our proposed mechanism in increasing throughput and network utilization by adjusting the background traffic on the paths.

SCTP (Stream Control Transmission Protocol) was proposed by IETF. It shows superior extensibility and compatibility as compared to other transport layer protocols, such as TCP and UDP. In addition, it supports multi-streaming and multi-homing. Although an SCTP connection can convey many video streams from different applications, it lacks the provision of different QoS for different streams in the same association. On the other hand, more and more mobile devices are equipped with multiple network (e.g., UMTS/WLAN) interfaces to transmit packets over 3G cellular networks or wireless local area networks. This thesis presents a dynamic chunk adjustment scheme for SCTP-based video streaming in an integrated UMTS and WLAN network. The proposed scheme can support QoS guarantees for different streams in an SCTP association whenever a mobile node moves across the two networks or remains service by either network. Besides, when a mobile node roams from a WLAN to a UMTS, the proposed ¡§deassociation¡¨ capability is applied to increase the channel utilization in 3G cellular networks. Performance evaluations on NS-2 are presented to demonstrate the effectiveness and the advantage of our proposed scheme over the original SCTP.

Networking research and development have historically focused on increasing network throughput and path resource utilization, which particularly helped bulk applications such as file transfer and video streaming. Recent over-provisioning in the core of the Internet has facilitated the use of interactive applications like interactive web browsing, audio/video conferencing, multi- player online gaming and financial trading applications. Although the bulk applications rely on transferring data as fast as the network permits, interactive applications consume rather little bandwidth, depending instead on low latency. Recently, there has been an increasing concern in reducing latency in networking research, as the responsiveness of interactive applications directly influences the quality of experience. To appreciate the significance of latency-sensitive applications for today's Internet, we need to understand their traffic pattern and quantify their prevalence. In this thesis, we quantify the proportion of potentially latency-sensitive traffic and its development over time. Next, we show that the flow start-up mechanism in the Internet is a major source of latency for a growing proportion of traffic, as network links get faster. The loss recovery mechanism in the transport protocol is another major source of latency. To improve the performance of latency-sensitive applications, we propose and evaluate several modifications in TCP. We also investigate the possibility of prioritization at the transport layer to improve the loss recovery. The idea is to trade reliability for timeliness. We particularly examine the applicability of PR-SCTP with a focus on event logging. In our evaluation, the performance of PR-SCTP is largely influenced by small messages. We analyze the inefficiency in detail and propose several solutions. We particularly implement and evaluate one solution that utilizes the Non-Renegable Selective Acknowledgments (NR-SACKs) mechanism, which has been proposed for standardization in the IETF. According to the results, PR-SCTP with NR-SCAKs significantly improves the application performance in terms of low latency as compared to SCTP and TCP. / Interactive applications such as web browsing, audio/video conferencing, multi-player online gaming and financial trading applications do not benefit (much) from more bandwidth. Instead, they depend on low latency. Latency is a key determinant of user experience. An increasing concern for reducing latency is therefore currently being observed among the networking research community and industry. In this thesis, we quantify the proportion of potentially latency-sensitive traffic and its development over time. Next, we show that the flow start-up mechanism in the Internet is a major source of latency for a growing proportion of traffic, as network links get faster. The loss recovery mechanism in the transport protocol is another major source of latency. To improve the performance of latency-sensitive applications, we propose and evaluate several modifications in TCP. We also investigate the possibility of prioritization at the transport layer to improve the loss recovery. The idea is to trade reliability for timeliness. We particularly examine the applicability of PR-SCTP with a focus on event logging. In our evaluation, the performance of PR-SCTP is largely influenced by small messages. We analyze the inefficiency in detail and propose several solutions. We particularly implement and evaluate one solution that utilizes the Non-Renegable Selective Acknowledgments (NR-SACKs) mechanism, which has been proposed for standardization in the IETF. According to the results, PR-SCTP with NR-SCAKs significantly improves the application performance in terms of low latency as compared to SCTP and TCP.

TCP and UDP are the most popular transport protocols used for end-end data transmission. The rapid growth of internet leads to development of many innovative applications in the current environment. Depending on the functionality of these applications, requirements of transport protocols are changing. TCP is known for its problems with Head Of Line blocking (HOL) and SYN attacks which gives reduced performance, and also doesn’t support Multi-Homing. SCTP is another transport layer protocol similar to TCP which provides end-end communication. It has some unique features like support for Multi-homing and multi-streaming. It also protects better from SYN attacks by using four-way hand shake mechanism during association establishment. As an extension to SCTP, CMT-SCTP was proposed to take full advantage of a multi-homed host by doing load sharing over multiple paths. SCTP is believed to be a next generation transport protocol. This thesis gives an overview of the SCTP protocol and its features focusing on analysing and testing of failover mechanisms provided by SCTP in multi-homed host, evaluating the transmission performance of SCTP vs TCP in a real network environment. This report also gives a theoretical analysis on how SCTP can mitigate SYN attacks by using four-way handshake mechanism and the state of art of CMT-SCTP.

With the rapid growth of communication, applications in traffic sensor network such as the multimedia service Server Push, are indispensable to business advertising. The applications of server push, for example, the service Push Mail provided by ISP (Internet Service Provider), became much more hot and popular. This paper aims to design a mobile vehicular network to let the people who received the advertisement communicate with the providers of the service. Nevertheless, the handoff problem that arises when traveling brings down the quality of communication. Therefore, seamless handoff becomes a very important issue for us to research. This thesis uses the new SCTP (Stream Control Transmission Protocol) to solve the problem. SCTP not only keeps the advantages of TCP/IP but also provides new support. Allowing the user to own several IP addresses at the same time is one of its important characteristics, which allows you to switch to any other available IP immediately if the transmission is interruptted. With this characteristic, the user barely notices any interruption in the process of handoff. Finally, we propose a new design for SCTP to achieve a response time, and can be used in applications that require a fast response time.