Dynamic Bandwidth Allocation in ATM Networks

Today's new applications such as World Wide Web, video conferencing and multimedia have introduced a large amount of traffic into the network. Additionally new applications are also heading towards real time process. Instant access to the network, greater level of performances and higher degree of satisfaction has become the main concerns of users using these new applications. Although current transmission mediums have advanced in capacity through means such as optical fiber and Gigabit Ethernet, future and unknown new services tend to consume up the available bandwidth. ATM network is the new technology used to support a wide variety of services including data, voice, video and most possibly other future applications. Its flexibility, efficiency and high throughput have gained popularity but with greater complexity due to different approaches in handling different type of services.A high-speed network such as ATM networks must have an effective traffic management scheme in order to gain high data throughput with the least cost of operation. Thus, simulation and modeling are the effective methods used to design the trade-off between network parameters and their performances. Effective sharing of network resources such as bandwidth and buffer are studied through the dynamic allocation method. Static allocation scheme has been proven inefficient to provide high resources utilization as can be seen in STM networks compared to A TM networks. However, ATM networks should provide different dynamic allocation methods according to its different services and traffic characteristics. Four dynamic allocation strategies have been designed, evaluated and compared for their performances. They are called Static Bandwidth Allocation, Bandwidth Allocated Proportional to Expected Queue Length, Bandwidth Allocated Proportional to Expected Queue Length with Threshold Value and Bandwidth Allocated with Threshold Interrupt. Bandwidth Allocated with Threshold Interrupt is proven to be the most effective strategy as it could response to congestion immediately

Energy-efficient wireless communication

In this chapter we present an energy-efficient highly adaptive network interface architecture and a novel data link layer protocol for wireless networks that provides Quality of Service (QoS) support for diverse traffic types. Due to the dynamic nature of wireless networks, adaptations in bandwidth scheduling and error control are necessary to achieve energy efficiency and an acceptable quality of service. In our approach we apply adaptability through all layers of the protocol stack, and provide feedback to the applications. In this way the applications can adapt the data streams, and the network protocols can adapt the communication parameters

TCP over High Speed Variable Capacity Links: A Simulation Study for Bandwidth Allocation

New optical network technologies provide opportunities for fast, controllable bandwidth management. These technologies can now explicitly provide resources to data paths, creating demand driven bandwidth reservation across networks where an applications bandwidth needs can be meet almost exactly. Dynamic synchronous Transfer Mode (DTM) is a gigabit network technology that provides channels with dynamically adjustable capacity. TCP is a reliable end-to-end transport protocol that adapts its rate to the available capacity. Both TCP and the DTM bandwidth can react to changes in the network load, creating a complex system with inter-dependent feedback mechanisms. The contribution of this work is an assessment of a bandwidth allocation scheme for TCP flows on variable capacity technologies. We have created a simulation environment using ns-2 and our results indicate that the allocation of bandwidth maximises TCP throughput for most flows, thus saving valuable capacity when compared to a scheme such as link over-provisioning. We highlight one situation where the allocation scheme might have some deficiencies against the static reservation of resources, and describe its causes. This type of situation warrants further investigation to understand how the algorithm can be modified to achieve performance similar to that of the fixed bandwidth case

DTMsim - DTM channel simulation in ns

Dynamic Transfer Mode (DTM) is a ring based MAN technology that provides a channel abstraction with a dynamically adjustable capacity. TCP is a reliable end to end transport protocol capable of adjusting its rate. The primary goal of this work is investigate the coupling of dynamically allocating bandwidth to TCP flows with the affect this has on the congestion control mechanism of TCP. In particular we wanted to find scenerios where this scheme does not work, where either all the link capacity is allocated to TCP or congestion collapse occurs and no capacity is allocated to TCP. We have created a simulation environment using ns-2 to investigate TCP over networks which have a variable capacity link. We begin with a single TCP Tahoe flow over a fixed bandwidth link and progressively add more complexity to understand the behaviour of dynamically adjusting link capacity to TCP and vice versa

Survey of congestion control techniques for an ATM network

The emerging broadband integrated services digital network is expected to adopt ATM (Asynchronous Transfer Mode) as the transport network. This new network must support several classes of service with varying delay and loss requirements. It must also operate with link speeds in the hundreds of megabits per second and be scalable up to potential link speeds on the order of gigabits per second. The requirements to support multiple services and high speed make the congestion control in an ATM network difficult. This paper reviews sorne of the techniques for prevention and control of congestion in an ATM network

Energy-efficient adaptive wireless network design

Energy efficiency is an important issue for mobile computers since they must rely on their batteries. We present an energy-efficient highly adaptive architecture of a network interface and novel data link layer protocol for wireless networks that provides quality of service (QoS) support for diverse traffic types. Due to the dynamic nature of wireless networks, adaptations are necessary to achieve energy efficiency and an acceptable quality of service. The paper provides a review of ideas and techniques relevant to the design of an energy efficient adaptive wireless networ

The Role of Responsive Pricing in the Internet

The Internet continues to evolve as it reaches out to a wider user population. The recent introduction of user-friendly navigation and retrieval tools for the World Wide Web has triggered an unprecedented level of interest in the Internet among the media and the general public, as well as in the technical community. It seems inevitable that some changes or additions are needed in the control mechanisms used to allocate usage of Internet resources. In this paper, we argue that a feedback signal in the form of a variable price for network service is a workable tool to aid network operators in controlling Internet traffic. We suggest that these prices should vary dynamically based on the current utilization of network resources. We show how this responsive pricing puts control of network service back where it belongs: with the users.Internet, pricing, feedback, networks

Equilibrium bandwidth and buffer allocations for elastic traffics

Consider a set of users sharing a network node under an allocation scheme that provides each user with a fixed minimum and a random extra amount of bandwidth and buffer. Allocations and prices are adjusted to adapt to resource availability and user demands. Equilibrium is achieved when all users optimize their utility and demand equals supply for nonfree resources. We analyze two models of user behavior. We show that at equilibrium expected return on purchasing variable resources can be higher than that on fixed resources. Thus users must balance the marginal increase in utility due to higher return on variable resources and the marginal decrease in utility due to their variability. For the first user model we further show that at equilibrium where such tradeoff is optimized all users hold strictly positive amounts of variable bandwidth and buffer. For the second model we show that if both variable bandwidth and buffer are scarce then at equilibrium every user either holds both variable resources or none