Transport congestion events detection (TCED): towards decorrelating congestion detection from TCP

TCP (Transmission Control Protocol) uses a loss-based algorithm to estimate whether the network is congested or not. The main difficulty for this algorithm is to distinguish spurious from real network congestion events. Other research studies have proposed to enhance the reliability of this congestion estimation by modifying the internal TCP algorithm. In this paper, we propose an original congestion event algorithm implemented independently of the TCP source code. Basically, we propose a modular architecture to implement a congestion event detection algorithm to cope with the increasing complexity of the TCP code and we use it to understand why some spurious congestion events might not be detected in some complex cases. We show that our proposal is able to increase the reliability of TCP NewReno congestion detection algorithm that might help to the design of detection criterion independent of the TCP code. We find out that solutions based only on RTT (Round-Trip Time) estimation are not accurate enough to cover all existing cases. Furthermore, we evaluate our algorithm with and without network reordering where other inaccuracies, not previously identified, occur

Measuring Round Trip Time and File Download Time of FTP Servers

Today, Internet is a public, cooperative, and self-sustaining facility accessible to hundreds of millions of people worldwide. It has made the world a global village. It uses a layered model such as TCP/IP. Data can transfer easily using ordinary file transfer method such as HTTP and emails protocols. When to transfer or download the large set of data like big collection of file via inexpensive IP networks then throughput collapses. New TCP stacks and new network acceleration devices are market to help .but fail to fully utilize many wide area network paths. Consequently, conventional FTP, and even new "acceleration" solutions, cannot provide the speed and predictability needed for global file transfers. There are some problems which may affect the download time.  It  may  include  the hardware/software  configurations,  location  of machines,  bandwidth,  delay, congestion, size  of  the files and other type of configurations problems. The response time of the FTP server and Round Trip Time (RTT) plays an important role in download time of a file. In this paper, we investigate the possible relationship between the Round Trip Time and the software download time for the FTP servers. It also shows the factors that could have an impact on the FTP server response time. In our experiment, we assume the existing infrastructure of the Internet with its current technologies and protocols. So we concluded that if the RTT is less, the download time will be less. We presented the Karn’s algorithm to improve the accuracy of RTT measurement. Keywords: File transport protocol, Round trip time, Karn’s algorithm, DNS response time, TCP/I

On detection algorithms for spurious retransmissions in TCP

In TCP, a spurious packet retransmission can be caused by either spurious timeout (STO) or spurious fast retransmit (SFR). The "lost" packets are unnecessarily retransmitted and the evoked congestion control process causes network underutilization. In this paper, we focus on spurious retransmission detection. We first present a survey on some important and interesting spurious retransmission detection algorithms. Based on the insights obtained, we propose a novel yet simple detection algorithm called split-and-retransmit (SnR). SnR only requires a minor modification to the TCP sender while leaving the receiver intact. The key idea is to split the retransmitted packet into two smaller ones before retransmitting them. As the packet size is different, the ACK triggered will carry different ACK numbers. This allows the sender to easily distinguish between the original transmission and the retransmission of a packet without relying on, e.g., TCP options. We then compare our SnR with STODER, F-RTO and Newreno under both loss-free and lossy network environments. We show that our SnR is resilient to packet loss and yields good performance under various simulation settings. ©2010 IEEE.published_or_final_versionThe 2010 IEEE Wireless Communications and Networking Conference (WCNC), Sydney, Australia, 18-21 April 2010. In Proceedings of WCNC, 2010, p. 1-

System Support for Bandwidth Management and Content Adaptation in Internet Applications

This paper describes the implementation and evaluation of an operating system module, the Congestion Manager (CM), which provides integrated network flow management and exports a convenient programming interface that allows applications to be notified of, and adapt to, changing network conditions. We describe the API by which applications interface with the CM, and the architectural considerations that factored into the design. To evaluate the architecture and API, we describe our implementations of TCP; a streaming layered audio/video application; and an interactive audio application using the CM, and show that they achieve adaptive behavior without incurring much end-system overhead. All flows including TCP benefit from the sharing of congestion information, and applications are able to incorporate new functionality such as congestion control and adaptive behavior.Comment: 14 pages, appeared in OSDI 200

Explorando posibles mejoras de protocolo TCP en redes móviles

En este trabajo se intenta realizar una mínima recopilación de los esfuerzos que se han realizado en adaptar al protocolo TCP (Transmission Control Protocol) a redes de datos en donde las tasas de error son mucho mayores que las tasas para el cual fue pensado originalmente este protocolo, debido a la congestión de datos. Así mismo intentaremos analizar que posibles mejoras pueden realizarse en la aplicación del protocolo TCP en redes móviles, en donde un enlace wireless interviene en uno o más de los trayectos de los datos e introduce dos fenómenos típicos de este enlace como son, la perdida de paquetes por diversas caudas o directamente el desacople de uno de los nodos.Eje: Arquitecturas, Redes y Sistemas OperativosRed de Universidades con Carreras en Informática (RedUNCI

Explorando posibles mejoras de protocolo TCP en redes móviles

En este trabajo se intenta realizar una mínima recopilación de los esfuerzos que se han realizado en adaptar al protocolo TCP (Transmission Control Protocol) a redes de datos en donde las tasas de error son mucho mayores que las tasas para el cual fue pensado originalmente este protocolo, debido a la congestión de datos. Así mismo intentaremos analizar que posibles mejoras pueden realizarse en la aplicación del protocolo TCP en redes móviles, en donde un enlace wireless interviene en uno o más de los trayectos de los datos e introduce dos fenómenos típicos de este enlace como son, la perdida de paquetes por diversas caudas o directamente el desacople de uno de los nodos.Eje: Arquitecturas, Redes y Sistemas OperativosRed de Universidades con Carreras en Informática (RedUNCI

Multimedia courseware for interactive teaching and learning: students’ needs and perspectives

Education faces many new challenges in meeting the demands of teaching and learning for the 21st century. One of the new challenges is to integrate ICT (Information and communication technologies) in teaching and learning as a means of delivering alternative teaching. Multimedia technology, for example, has the potential to transform a traditional classroom into an unlimited imaginary world. This paper report on development and evaluation of a multimedia courseware for Design and Technology (RBT). An interactive CD was developed using the Adobe Flash CS6 software. Alpha and Beta testing have been carried out in the development process. 6 experts were assigned to evaluate the functionality of the interactive CD. In order to identify the usability of interactive CD, 103 respondents were involved in the survey by filling four-point Likert scaled questionnaire. The findings show that, the level of interactive CD usability is at a high level. Based on this study, there are positive effects that we can see based on the use of multimedia elements in the education system. The meaningful benefits of using multimedia elements for learning include the presentation of various learning styles. The presentation of information usually integrates multimedia elements such as text, graphics, audio and video