Bharath Kumar Kadaba

The AURORA gigabit testbed

Abstract AURORA is one of five U.S. networking testbeds charged with exploring applications of, and technologies necessary for, networks operating at gigabit per second or higher bandwidths. The emphasis of the AURORA testbed, distinct from the other four testbeds, BLANCA, CASA, NECTAR and VISTANET, is research into the supporting technologies for gigabit networking. Like the other testbeds, AURORA itself is an experiment in collaboration, where government initiative (in the form of the Corporation for National Research Initiatives, which is funded by DARPA and the National Science Foundation) has spurred interaction among pre-existing centers of excellence in industry, academia, and government. AURORA has been charged with research into networking technologies that will underpin future high-speed networks. This paper provides an overview of the goals and methodologies employed in AURORA, and points to some preliminary results from our first year of research, ranging from analytic results to experimental prototype hardware. This paper enunciates our targets, which include new software architectures, network abstractions, and hardware technologies, as well as applications for our work.

An overview of the AURORA gigabit testbed

AURORA is one of five US testbeds charged with exploring applications of, and technologies necessary for, networks operating at gigabit per second or higher bandwidths. The authors provide an overview of the goals and methodologies employed in AURORA and report preliminary results from the first year of research. AURORA is an experiment in collaboration, where government support has spurred interaction among centers of excellence in industry, academia, and government. The emphasis of the AURORA testbed is research into the supporting technologies for gigabit networking. The targets include new software architectures, network abstractions, hardware technologies, and applications. The AURORA testbed will provide a platform in which researchers can explore business and scientific applications of gigabit networks, while evolving the network architecture to meet the needs of these emerging applications.<<ETX>>

Network delay considerations for packetized voice

Abstract The potential cost benefit from integrating data and voice in a single network provides a strong motivation for packetized voice transmission. In this study, simulation models are used to characterize the delay distribution of voice packets in a single hop as well as in a multi-hop network environment. The trade-off between the number of speakers that can be multiplexed using speech activity detection technique and the delay performance are quantified. This is contrasted with the performance obtained by using a lower bit-rate voice input without speech activity detection. Finally, a procedure is presented which guarantees that the delay for any packet belonging to a call will not exceed a given value throughout the duration of the call, once the call is set up. This procedure can be used with or without speech activity detection.

A Critique of ATM from a Data Communications Perspective

Fast Packet Switching (FPS) is emerging as the preferred technology for future high speed, integrated networks. Asynchronous Transfer Mode (ATM) is an approach to FPS that is in the process of standardization and is the preferred approach of the carrier community. Concurrently, alternative approaches to FPS based on variable sized packets have been proposed by segments of the data communication industry. These approaches include Frame Relay and an approach developed by IBM called PARIS. The purpose of this paper is to examine the suitability of ATM for data communications relative to some of these alternative approaches.

Analysis of a class of distributed directory algorithms

Three directory schemes are investigated: the local cache (LC) scheme in which there is a cache at the network nodes to store the results of a previous query for a remote resource so that a subsequent query for that resource can be resolved locally, and two enhancements of this scheme, namely the regional cache server (RCS) scheme and the cooperating cache servers (CCS) scheme, in which the queries not resolved locally are funneled through designated nodes or servers to reduce multiple network searchers for a given resource. The performance of these schemes in terms of the network search rate is dependent on the cache sizes at the nodes and servers, the probability distribution for queuing resources, and the cache replacement policy used to displace resources from the cache to accommodate newly discovered ones. Two policies are investigated: A/sub 0/, which is the optimal policy for the LC scheme, and the least recently used policy, which is of practical importance.<<ETX>>

Selective load redistribution in packet-switched networks

A design is presented for rerouting existing sessions (virtual circuits) under certain conditions to improve the routing performance. The authors call this mechanism selective load redistribution (SLRD). SLRD is a fully distributed algorithm which redistributes sessions in parallel at different nodes by carefully selecting the amount of traffic to be switched. The performance of the algorithm is evaluated by a simulation model. The results for several sample networks show that the algorithm performs very well even though the information available to the nodes for route computation may not be completely accurate.<<ETX>>

A distributed directory scheme in computer networks

In this scheme, each node in the network maintains a local DDB (directory database), and each resource i is registered in the DDBs of all nodes with r/sub i/ hops away from the owning node of resource i, where r/sub i/ denotes the radius of the resource. In general, each resource has a different radius. Whenever a user at a node makes a reference to a resource, the node first searches its local DDB to find an entry for the resource. If this attempt is successful, it is done. Otherwise, the node trigger a query protocol to find the resource. Registered entries are updated for the integrity of stored information every time there are changes in their contents. This scheme uses simple broadcast protocols among the nodes in the network in querying other nodes to find a nonlocal resource and in updating DDBs of other nodes. The authors quantify the response time performance and the overhead associated with the directory scheme as a function of the radius of each resource, and propose an integer programming formulation to determine the optimal radius for each resource which is solved in O(R) steps, where R is the maximum radius of the resource.<<ETX>>