Showing papers by "Sonia Fahmy published in 1999"

Traffic management for TCP/IP over satellite ATM networks

Abstract: Several Ka-band satellite systems have been proposed that will use ATM technology to seamlessly transport Internet traffic. The ATM UBR, GFR, and ABR service categories have been designed for data. However, several studies have reported poor TCP performance over satellite ATM networks. We describe techniques to improve TCP performance over satellite ATM networks. We first discuss the various design options available for TCP end systems, IP-ATM edge devices, as well as ATM switches for long-latency connections. We discuss buffer management policies, guaranteed rate services, and the virtual source/virtual destination option in ATM. We present a comparison of ATM service categories for TCP transport over satellite links. The main goal of this article is to discuss design and performance issues for the transport of TCP over UBR, GFR, and ABR services for satellite ATM networks.

AQuaFWiN: adaptive QoS framework for multimedia in wireless networks and its comparison with other QoS frameworks

Abstract: In a wireless environment, due to topology changes and characteristics of media (interference in radio signals) the bandwidth of a link is unpredictable and possibly very low, the error rates are variable and extremely high. Provisioning and guaranteeing quality of service (QoS) in such an environment is a very challenging problem. In this paper we propose an adaptive and QoS framework to support multimedia applications in a wireless networking environment. The proposed framework is hierarchical in nature with cluster of mobile end hosts connected to a base station, base stations are connected to a supervisory node, which in turn is connected to the wired infrastructure. The changing conditions in wireless due to interference and possibly mobility, entitle that the real-time applications needing stringent QoS should be adaptable. The framework uses a generic feedback mechanism to support adaptability at all layers of the wireless network. An overview of existing wireless architectures which support QoS is given. The architectures discussed are WAMIS (wireless adaptive multimedia information system), SWAN (seamless wireless ATM network), MMWN (multimedia support for mobile wireless networks), and QGMC (QoS guarantees in mobile computing). The proposed approach is compared with these existing methods.

QoS and multipoint support for multimedia applications over the ATM ABR service

Abstract: Multimedia applications with stringent delay requirements are usually supported by the constant bit rate (CBR) or real-time variable bit rate (rt-VBR) service categories of ATM. This article shows that the available bit rate (ABR) service, which was originally designed for data, can also support multimedia applications under certain circumstances. Issues related to the design of proper ABR traffic management algorithms for such support are presented.

Traffic Management in ATM Networks Over Satellite Links

Abstract: This report presents a survey of the traffic management Issues in the design and implementation of satellite Asynchronous Transfer Mode (ATM) networks. The report focuses on the efficient transport of Transmission Control Protocol (TCP) traffic over satellite ATM. First, a reference satellite ATM network architecture is presented along with an overview of the service categories available in ATM networks. A delay model for satellite networks and the major components of delay and delay variation are described. A survey of design options for TCP over Unspecified Bit Rate (UBR), Guaranteed Frame Rate (GFR) and Available Bit Rate (ABR) services in ATM is presented. The main focus is on traffic management issues. Several recommendations on the design options for efficiently carrying data services over satellite ATM networks are presented. Most of the results are based on experiments performed on Geosynchronous (GEO) latencies. Some results for Low Earth Orbits (LEO) and Medium Earth Orbit (MEO) latencies are also provided.

Overload based explicit rate switch schemes with MCR guarantees

Abstract: An explicit rate switch scheme monitors the load at each link and gives feedback to the sources. We define the overload factor as the ratio of the input rate to the available capacity. In this paper, we present three overload-based switch schemes which provide MCR (minimum cell rate) guarantees for the ATM (asynchronous transfer mode) ABR (available bit rate) service. The switch schemes proposed use the overload factor and other terms including current source rate and target utilization to calculate feedback rates. A dynamic queue control mechanism is used to achieve efficient usage of the link, control queues and, achieve constant queuing delay at steady state. The proposed algorithms are studied and compared using several configurations. The configurations were chosen to test the performance of the algorithms in the presence of link bottlenecks, source bottlenecks and transient sources. Finally, a comparison of the proposed algorithms based on the simulation results is given.

QoS and Multipoint Support for Multimedia Applications over the

Abstract: Multimedia applications with stringent delay requirements are ABSTRACT usually supported by the CBR or rt-VBR service categories of ATM. This article shows that ABR service, which was originally designed for data, can also support multimedia applications under certain circumstances. Issues related to the design of proper ABR traffic management algorithms for such support are presented. to get the connection rejected. In such cases, ABR service is preferable. Also, with a CBR or VBR connection, the synchronous transfer mode (ATM) is a cell-switch- A ing connection-oriented high-speed technology. The ATM Forum has defined five service categories: constant bit rate (CBR), real-time variable bit rate (rt-VBR), non real- time VBR (nrt-VBR), available bit rate (ABR), and unspeci- fied bit rate (UBR). The International Telecommunication Union - Telecommunication Standardization Sector (ITU-T) defines similar service categories for ATM. CBR and rt-VBR provide delay and loss guarantees, and can be used to transfer delay- and loss-sensitive unadaptive multimedia applications. Nrt-VBR provides loss guarantees. ABR and UBR are usually used for transferring data applications. UBR is a simple ser- vice that gives no guarantees. ABR provides minimum cell rate (MCR) guarantees and is designed to provide low cell loss for well-behaving sources. It uses closed-loop feedback control to indicate network conges- tion information to the sources. The sources adjust their allowed cell rate (ACR) based on the network feedback. Feedback is indicated in resource management (RM) cells, which are periodically sent by the source and turned around by the destination. The switches along the path indicate the maximum rate they can currently support in the RM cell. The RM cells in the forward direction are called forward RM (FRM) cells, and those in the backward direction backward