Best effort measurement based congestion control

Abstract available: p.

Study of TCP Issues over Wireless and Implementation of iSCSI over Wireless for Storage Area Networks

The Transmission Control Protocol (TCP) has proved to be proficient in classical wired networks, presenting an ability to acclimatize to modern, high-speed networks and present new scenarios for which it was not formerly designed. Wireless access to the Internet requires that information reliability be reserved while data is transmitted over the radio channel. Automatic repeat request (ARQ) schemes and TCP techniques are often used for error-control at the link layer and at the transport layer, respectively. TCP/IP is becoming a communication standard [1]. Initially it was designed to present reliable transmission over IP protocol operating principally in wired networks. Wireless networks are becoming more ubiquitous and we have witnessed an exceptional growth in heterogeneous networks. This report considers the problem of supporting TCP, the Internet data transport protocol, over a lossy wireless link whose features vary over time. Experimental results from a wireless test bed in a research laboratory are reported

Data adaptor unit for an electronic exchange: system design and simulation study

The development of pulse code modulation systems and electronic exchanges, together with the increase in volume of data traffic, have made it desirable to establish a means for handling both voice and data trarfic in the telephone network. A technique is required whereby integrated voice and data switching may be accomplished in an electronic exchange. It is proposed that a data adaptor unit be incorporated in electronic exchanges for the ourpose of concentrating data traffic onto PCM highways. A conceptual design for the architecture of such a unit is presented and its performance evaluated. The protocols for connecting data adaptors into a network, and the use of flow control procedures for regulating data traffic within the network, are described. The hardware implementation of the unit is not considered. The proposed data adaptor operates on the packet switching principle. It is comprised of three types of modules each dedicated to carrying out a particular communication function. The modules are the interface processor that interacts with data transmitting devices, the network processor for sending data over PCM channels between adaptors, and the supervisory processor for regulating activities within the adaptor unit

Design and evaluation of protocols for wireless networks taking into account the interaction between transport and network layers.

We recognized two important shortcomings of the current TCP protocol: misinterpretation of delayed acknowledgments and competition among different TCP flows. In this dissertation, we propose to address these two issues by a use of novel protocol that uses immediate and delayed acknowledgment schemes and provides a coordination mechanism among independent TCP flows. We also address certain important issues that are related to the implementation of our proposed protocol: can we maintain the end-to-end semantics of TCP? Are there additional benefits that can be harvested if intermediate nodes with TCP protocol can be used? (Abstract shortened by UMI.)The Transmission Control Protocol (TCP) provides end-to-end data reliability and is the primary transport layer protocol for many applications such as email, web access, and file transfer. There has been a plethora of research activity that aims to improve the performance of TCP both in wired and wireless networks. Protocols for the computer networks have been very structured and layered to allow for easier upgrades and maintenance. The network layer protocol (e.g. IP) is independent and below the transport layer protocol (e.g. TCP). Our main goal in this dissertation is to examine the interaction and dynamics between the network layer protocols and TCP in the wireless environment.Towards this goal, we examined the network layer protocols in one-hop wireless (e.g. cellular networks) and multi-hop wireless, e.g. distributed Wi-Fi (Wireless Fidelity) networks. For each of these networks we, for the first time, propose transport layer protocols that take into account the interaction between the network layer and transport layer. For the one-hop wireless networks we have investigated analytical methods to determine the buffer requirements at base stations and estimate disruption time which is the time between two packet arrivals at the mobile host. We will show that the estimation of buffer requirements and disruption time is not only dependent on the wireless TCP scheme used, but also its interaction with the underlying network protocol. We also propose a comprehensive study of the effectiveness of wireless TCP and network protocols taking into account different networking environments that is decided on many factors such as mobility of senders and receivers, simplex and duplex communication among communicating peers, connection oriented and connection less communication at the network layer, rerouting schemes used after movement, and with and without hint handoff schemes

Decentralizing UNIX abstractions in the exokernel architecture

Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 1997.Includes bibliographical references (p. 49-51).by Héctor Manuel Briceño Pulido.M.Eng

Evaluation of a Set of TCP Features over Narrowband Radio Bearer for Train Communication

An engineering approach to the evaluation of the TCP as a narrowband bearer for short messages in the low latency train-trackside communication scenario is described in this report. The project was developed in cooperation with Bombardier Transportation Sweden AB as a part of the “ETCS over GPRS” venture. With the increase of the demands from the railway industry, the currently used circuit-switched GSM-R technology becomes unsatisfactory from the radio system capacity point of view and the need of a new solution is highly required. The packet-switched GPRS solution using TCP as a suite is under research for this specific scenario. The investigated problem in this report concerns the tuning of the retransmission mechanism, which includes the TCP features TCP_RTO_MIN and TCP_KEEPALIVE. This implies the tuning of those features to be able to detect a loss of communication and to react less aggressively for the short and instantaneous changes in the network delay. This thesis work began with a preparation phase in which a broad literature analysis of the background theory was made and followed by the development of applications that realizes the traffic model. Later in the performance phase the required changes were applied on the system and finally tested in a lab. The tests have been performed using one and four pairs of client-server applications communicating over an emulated link. The TCP features were modified at two levels, the TCP_RTO_MIN by a kernel recompilation and the TCP_KEEPALIVE by changes on the live system. Results from the tests have shown that for the higher than the default value of the TCP_RTO_MIN the less retransmissions were triggered. The TCP_KEEPALIVE has proven to be a sufficient feature to indicate a loss of the link. However the achieved improvement in performance was not as high as expected, but acceptable for this scenario. The train-trackside communication system could benefit from the proposed changes

Autonomic Systems

An autonomic system is defined as self-configuring, self-optimizing, self-healing, and self-protecting. We implemented the Autonomic Cluster Management System (ACMS), a low overhead Java application designed to manage and load balance a cluster, while working at NASA GSFC. The ACMS is a mobile multi-agent system in which each agent is designed to fulfill a specific role. The agents collaborate and coordinate their activities in order to achieve system management goals. The ACMS is scalable and extensible to facilitate future development