Network protocol changes can improve DisCom WAN performance : evaluating TCP modifications and SCTP in the ASC tri-lab environment.

현재 인터넷에서는 객체를 전송하기 위해 HTTP over TCP가 사용된다. SCTP는 TCP의 문제점을 보완하기 위해 제안된 프로토콜로 개별적인 스트림을 이용하여 데이터를 전송하므로 웹 객체의 평균 응답 시간을 감소시킬 수 있다. 본 논문에서는 HTTP over SCTP의 평균 응답 시간을 추정하는 해석적 모델을 개발함으로써 TCP에 대한 SCTP의 효과를 추정하고자 한다. TCP 지연을 구하기 위한 기존의 해석적 모델이 주로 유선 환경을 가정한데 비해, 본 연구에서 제안하는 모델은 다중 패킷 손실이 발생하고, 빠른 재전송이 가능하지 않은 무선 환경을 가정한다. 추정된 평균 응답 시간은 실제 웹 응용을 개발할 때, 종단 사용자의 서비스 품질을 만족시키기 위한 사전 벤치마크로 사용될 수 있다. 추정 모델의 타당성을 검증하기 위해 테스트베드 상에서 성능 실험을 수행한 결과, 모델과 실험결과의 차이가 평균 6% 이내로 매우 작으며, 동시에 HTTP over SCTP의 평균 전송 시간이 HTTP over TCP의 평균 전송 시간보다 작은 것으로 확인되었다. Hyper text transfer protocol (HTTP) over transmission control protocol (TCP) is currently used to transfer objects in the Internet. Stream control transmission protocol (SCTP), an alternative to TCP, which allows for independent delivery among streams, and can thus reduce the mean response delay of web object. We present an analytical model to find the mean response delay for HTTP over SCTP, therefore, estimate the effectiveness of SCTP over TCP. Typical TCP delay models assume the wired environment. On the contrary, the proposed model in this paper assumes the multiple packet losses and wireless environment where fast retransmission is not possible due to small window. The estimated mean response time can be used the benchmark to meet quality of service (QoS) at end-user. We validate the accuracy of our model using experiments. It is shown that the differences between the results from model and those from experimental are very small below 6 % on average. We also find that the mean response delay for HTTP over SCTP is less than that for HTTP over TCP.

Most current web application use HTTP (Hyper Text Transfer Protocol) and TCP (Transmission Control Protocol) to retrieve objects from the Internet. SCTP (Stream Control Transmission Protocol) is recently proposed transport protocol with congestion control mechanism similar to that of TCP. Waiting delay is an important performance criterion for when transferring web object over the Internet. In this paper, we present an analytical model of mean waiting delay for object transfers over the Internet in a wireless using the SCTP as the transport protocol and compare with the mean waiting in using TCP. Validation of the model using experimental results show that the mean waiting delay for HTTP over SCTP is less than that for HTTP over TCP. This is caused by the small slow-start time of SCTP.

SCTP is a transport layer protocol mainly designed for transferring public switched telephone network signalling over IP networks. Some of the protocols that support data transmission are transmission control protocol (TCP), user datagram protocol (UDP), and stream control transmission protocol (SCTP). SCTP is a newly invented reliable, message-oriented transport protocol. It is similar to TCP and UDP with some additional features such as multi-streaming and multi-homing. Even though it is a new protocol with some advanced features, there is a security loophole issue in data transmission using SCTP. Hence, we proposed a new technique to transmit a secret message by hiding it in a secret matrix using the advanced features of SCTP. The simulation of our proposed method provides better performance and high security for secret message transmission against network attacks.

The Stream Control Transmission Protocol (SCTP) is a relatively new transport protocol. It has several underlying mechanisms that are similar to the Transmission Control Protocol (TCP), as well as several improvements that are important in certain classes of applications. The timeout scheme of SCTP, however, is almost identical to that used in TCP. With dynamics of today's Internet, that timeout scheme may be too passive. This paper presents an algorithm which dynamically adjusts the overall context of the retransmission timeout process without changing the fundamental retransmission mechanisms. This approach manages the impact of fast retransmissions and timeouts to significantly improve the throughput of SCTP applications. The algorithm avoids spurious retransmissions and provides better throughput by intelligently managing RTO boundaries and allowing conventional timeout schemes to participate more actively in the retransmission process.

The Stream Control Transmission Protocol (SCTP) is a transport layer protocol introduced to complement the well known User Datagram Protocol (UDP) and the Transmission Control Protocol (TCP). The current implementation of SCTP heavily leverages some existing mature techniques from TCP. This paper studies the effect that RTOmin (retransmission timeout minimum) has on the selective acknowledgement (SACK), fast retransmission, and timeout mechanisms. We show that there are optimization opportunities in the manipulation of RTOmin while not significantly affecting timeout values and number of fast retransmissions. We demonstrate that RTOmin plays a balancing role in the trigger of timeouts and fast retransmissions and conclude that a dynamically set RTOmin would yield significant time-to-complete (throughput) improvements for SCTP based applications.

The Stream Control Transmission Protocol (SCTP) is a reliable transport protocol to tackle the limitations of TCP and UDP. SCTP was originally designed to transport PSTN signaling messages over IP networks, but is also capable of serving as a general-purpose transport protocol. SCTP provides attractive features such as multi-streaming and multi-homing that may be helpful in high-mobility environment. SCTP congestion control mechanisms are based upon TCP congestion principals with the exception of the fast recovery algorithm. Original SCTP congestion control can perform badly in high-speed wide area networks because of its slow response with large congestion window. We proposed a new congestion control scheme based on the simple congestion window modification for SCTP to improve its performance in high-speed wide area networks. The results of several experiments we performed proved that our new suggested congestion control scheme for SCTP in high-speed network improved the throughput of the original SCTP congestion control scheme significantly.

This report is in response to the Omnibus Appropriations Act, 2009 (H.R. 1105; Public Law 111-8) in its funding of the National Nuclear Security Administration's (NNSA) Advanced Simulation and Computing (ASC) Program. This bill called for a report on ASC's plans for computing and platform acquisition strategy in support of stockpile stewardship. Computer simulation is essential to the stewardship of the nation's nuclear stockpile. Annual certification of the country's stockpile systems, Significant Finding Investigations (SFIs), and execution of Life Extension Programs (LEPs) are dependent on simulations employing the advanced ASC tools developed over the past decade plus; indeed, without these tools, certification would not be possible without a return to nuclear testing. ASC is an integrated program involving investments in computer hardware (platforms and computing centers), software environments, integrated design codes and physical models for these codes, and validation methodologies. The significant progress ASC has made in the past derives from its focus on mission and from its strategy of balancing support across the key investment areas necessary for success. All these investment areas must be sustained for ASC to adequately support current stockpile stewardship mission needs and to meet ever more difficult challenges as the weapons continue to age or undergo refurbishment. The appropriations bill called for this report to address three specific issues, which are responded to briefly here but are expanded upon in the subsequent document: (1) Identify how computing capability at each of the labs will specifically contribute to stockpile stewardship goals, and on what basis computing time will be allocated to achieve the goal of a balanced program among the labs. (2) Explain the NNSA's acquisition strategy for capacity and capability of machines at each of the labs and how it will fit within the existing budget constraints. (3) Identify the technical challenges facing the program and a strategy to resolve them.

TCP (transmission control protocol) is the prevalent reliable transport protocol used for many of the Internet's most popular services like Web browsing and e-mail. Since these services are the dominant applications on the Internet, TCP can be said to control the large majority of today's Internet traffic and we can say the enhancement of TCP performance means the improvement of the most Internet performance. In this paper, we compare various ACK generation TCP strategies that play very important roles in TCP operation and propose advanced delayed ACK algorithms to mitigate the negative effect of delayed ACK algorithm. Even if delayed ACK has a bright side to save network resources and power consumption that are the very important factors especially for mobile and wireless environments, it has also a dark side not to take full advantage of network bandwidth in the slow start phase. It is reported that delayed ACK timeout of the first and last segment causes a severe degradation problem in TCP throughput performance. We suggest new algorithms to solve delayed ACK penalty and to guarantee fairness with other traffic in slow start. In wired-cum-wireless network environments, BADA (base station aided delayed ACK) with SNDA (sender notification delayed ACK), the combination of our proposed algorithm shows the best performance in terms of throughput as well as in terms of network resource sharing. Our simulation shows significantly improved performance in TCP throughput.

The Stockpile Stewardship Program (SSP) is an integrated technical program for maintaining the safety, surety, and reliability of the U.S. nuclear stockpile. The SSP incorporates nuclear test data, computational modeling and simulation, and experimental facilities to advance understanding of nuclear weapons. The suite of data analyzed comes from activities including stockpile surveillance, experimental research, and development and engineering programs. This integrated national program requires the continued use of experimental facilities and the computational capabilities to support the SSP missions. These component parts, in addition to an appropriately scaled production capability, enable the National Nuclear Security Administration (NNSA) to support stockpile requirements. The ultimate goal of the Stewardship Program, and thus the Advanced Simulation and Computing (ASC) Program, is to ensure that the U.S. maintains a safe, secure, and effective strategic deterrent.

Transport layer reneging

Currently, the new transport protocol, Stream Control Transmission Protocol (SCTP), is not ECN-capable. The ECN-capable SCTP is proposed in this paper, which is bandwidth-efficient and robust to non-congestion losses. A SCTP source needs to adjust its congestion window when receiving ECN messages. We find the optimal value of the congestion window for a SCTP source in response to ECN messages, and develop a simple and practical method to achieve this optimal congestion window. Our simplified method in achieving the optimal congestion window is attractive because the total goodput performance of SCTP associations or the bottleneck link utilization is not sensitive to the window reduction policies when the network load is heavy. Using complicated methods to fine-tune SCTP or TCP's congestion window in response to congestion indications may be not worth the increase in complexity of the protocol.

Stream control transmission protocol (SCTP) is a new reliable transport layer protocol. This paper analyzes the performance of the SCTP for IPTV applications using the SCTP distinctive features such as partial-reliable SCTP (PR-SCTP) and multi-streaming. From the experimental results, it is shown that the PR-SCTP provides better goodput than TCP and better quality of services than UDP for real-time IPTV applications. From the viewpoint of the multi-streaming feature, it is shown that the SCTP overcomes the well-known head-of-line (HoL) blocking problems when multiple streams are transported over the SCTP. In addition, the multi-streaming SCTP gives faster channel switching time, compared to the TCP.

The DOE National Nuclear Security Administration (NNSA) Stockpile Stewardship Program (SSP) is an integrated technical program for maintaining the safety, security, and reliability of the U.S. nuclear stockpile. The SSP incorporates nuclear test data, computational modeling and simulation, and experimental facilities to advance understanding of nuclear weapons. The suite of data analyzed comes from activities including previous nuclear tests, stockpile surveillance, experimental research, and development and engineering programs. This integrated national program requires the continued use of experimental facilities and the computational capabilities to support the SSP missions. These component parts, in addition to an appropriately scaled production capability, enable NNSA to support stockpile requirements. The ultimate goal of the SSP, and thus of the Advanced Simulation and Computing (ASC) program, is to ensure that the U.S. maintains a safe, secure, and effective strategic deterrent.

One of only two new transport protocols introduced in the last 30 years is the Stream Control Transmission Protocol (SCTP). SCTP enables capabilities like additional throughput and fault tolerance for multihomed hosts. An SCTP implementation is included with the Linux kernel and another implementation called sctplib functions successfully in userspace on several platforms but unfortunately neither of these implementations have all of the latest features nor do they perform as well as the FreeBSD kernel implementation of SCTP. We were motivated to produce a portable implementation of the FreeBSD kernel SCTP stack that operates in userspace of any system because of both our desires to obtain a higher performance SCTP stack for Linux as well as to exploit recent developments in hardware virtualization and transport protocol onloading. Unlike any other userspace transport implementation for TCP or SCTP, our userspace SCTP stack simultaneously achieves similar throughput and latency as the Linux kernel TCP stack, without compromising on any of the transport's features as well as maintaining true portability across multiple operating systems and devices. We create a callback API and implement a threshold to control its usage; our userspace SCTP stack with these optimizations obtains higher throughput than the Linux kernel implementation of SCTP. We describe our userspace SCTP stack's design and demonstrate how it gives similar throughput and latency on Linux as the kernel TCP implementation, with the benefits of the new features of SCTP.

In recent years, a lot of performance evaluation methodologies and tools have been developed within disparate research communities for the purposes of evaluation, design, and model reduction. Among those as a free and powerful evaluation tool, ns2 has attracted more and more users who focus on developing/designing various network protocols. On the other hand, stream control transmission protocol (SCTP) natively supports multi-streaming feature and reorders the out-of-order data chunks, which are stored in stream buffer, based on the stream sequence number (SSN) as per individual stream. Nevertheless, SSN has a 16-bit size and the SCTP receiver of ns2 simply arranges the stored data chunks by the order of their SSNs without other preconditions. In the long-lived SCTP association, however, this may result in a permanent reordering confusion in stream buffer while SSN of any stream wraps back to zero and the stream buffer is not empty then. Eventually, this problem will lead to traffic interruption because of the overflow of the whole receiving buffer and unfortunately impact the evaluation result of the related ideas. This paper points out the potential fatal reordering problem and introduces a simple solution to permanently eliminate this issue. The feasibility of this solution has been proven in our simulations.