Mobile computing environments that seek to support communication-intensive applications need to provide sustained end-to-end networking resources to static and mobile flows in the presence of scarce and variable wireless bandwidth, bursty wireless channel error, and user mobility. In order to achieve this goal, we present the TIMELY adaptive resource management architecture and algorithms for resource reservation, advance reservation, and network layer and end-to-end adaptation in mobile computing environments. The key novelty of our approach is the coordination of adaptation between the different layers of the network in order to solve the problems introduced by scarce and dynamic network resources. 1 Introduction Mobile computing is becoming increasingly popular because of the availability of indoor and outdoor wireless packet networks such as Wavelan, Rangelan, RAM and CDPD. In order to effectively support communication-intensive applications such as web browsing and multime...

The Resilient Packet Ring (RPR) IEEE 802.17 standard is a new technology for high-speed backbone metropolitan area networks. A key performance objective of RPR is to simultaneously achieve high utilization, spatial reuse, and fairness, an objective not achieved by current technologies such as SONET and Gigabit Ethernet nor by legacy ring technologies such as FDDI. The core technical challenge for RPR is the design of a bandwidth allocation algorithm that dynamically achieves these three properties. The difficulty is in the distributed nature of the problem, that upstream ring nodes must inject traffic at a rate according to congestion and fairness criteria downstream. Unfortunately, we show that under unbalanced and constant-rate traffic inputs, the RPR fairness algorithm suffers from severe and permanent oscillations spanning nearly the entire range of the link capacity. Such oscillations hinder spatial reuse, decrease throughput, and increase delay jitter. In this paper, we introduce a new dynamic bandwidth allocation algorithm called Distributed Virtualtime Scheduling in Rings (DVSR). The key idea is for nodes to compute a simple lower bound of temporally and spatially aggregated virtual time using per-ingress counters of packet (byte) arrivals. We show that with this information propagated along the ring, each node can remotely approximate the ideal fair rate for its own traffic at each downstream link. Hence, DVSR flows rapidly converge to their ring-wide fair rates while maximizing spatial reuse. To evaluate DVSR, we develop an idealized fairness reference model and bound the deviation in service between DVSR and the reference model, thereby bounding the unfairness. With simulations, we find that compared to current techniques, DVSR's convergence times are an orde...

Mobile computing environments that seek to support communication-intensive applications need to provide sustained end-to-end networking resources to static and mobile flows in the presence of scarce and variable wireless bandwidth, bursty wireless channel error, and user mobility. In order to achieve this goal, we present the design and implementation of a new resource management architecture and algorithms for resource reservation, advance reservation and resource adaptation in mobile computing environments. In this technical report, we present a service model that captures the requirements of both stationary and mobile multimedia flows in a mobile computing environment, and propose a resource adaptation approach that maximizes the resource allocation for stationary flows and minimizes the variance in resource allocation for mobile flows in such environments. We introduce the notion of `network revenue' for resource adaptation, and present a rate adaptation algorithm that allocates ra...

The rate control mechanism for available-bit-rate (ABR) traffic as defined by the ATM Forum does not distinguish between different types of ABR connections. However, since ABR traffic may result from a heterogeneous set of applications, there is an apparent need for a flow control scheme that can distinguish between and give differential treatment to different classes of ABR connections. In this study, a multi-level flow control scheme for ABR traffic is proposed that performs flow control of ABR traffic simultaneously at three levels: At the first level, the scheme determines the total available ABR bandwidth at a link. At the second level, the ABR bandwidth is distributed to different ABR traffic classes. At the third level, the scheme determines the bandwidth available to connections in same traffic class. It is shown that the multi-level flow control method completely decouples the explicit rate calculation of distinct traffic classes while achieving a high network utilization. Extensive silmulations demonstrate that the multi-level flow control quickly adapts to load changes in the network.