Maximilian Ott

OMF: a control and management framework for networking testbeds

Networking testbeds are playing an increasingly important role in the development of new communication technologies. Testbeds are traditionally built for a particular project or to study a specific technology. An alternative approach is to federate existing testbeds to a) cater for experimenter needs which cannot be fullled by a single testbed, and b) provide a wider variety of environmental settings at different scales. These heterogenous settings allow the study of new approaches in environments similar to what one finds in the real world. This paper presents OMF, a control, measurement, and management framework for testbeds. It describes through some examples the versatility of OMFs current architecture and gives directions for federation of testbeds through OMF. In addition, this paper introduces a comprehensive experiment description language that allows an experimenter to describe resource requirements and their configurations, as well as experiment orchestration. Researchers would thus be able to reproduce their experiment on the same testbed or in a different environment with little changes. Along with the efficient support for large scale experiments, the use of testbeds and support for repeatable experiments will allow the networking field to build a culture of cross verification and therefore strengthen its scientific approach.

ORBIT testbed software architecture: supporting experiments as a service

This paper presents the software architecture of the ORBIT radio grid testbed. We describe the requirements for supporting the lifecycle of an experiment and how they influenced the overall design of the architecture. We specifically highlight those components and services which will be visible to a user of the ORBIT testbed.

Paying for QoS: an optimal distributed algorithm for pricing network resources

Network applications require certain individual performance guarantees that can be provided if enough network resources are available. Consequently, contention for the limited network resources may occur. For this reason, networks use flow control to manage network resources fairly and efficiently. This paper presents a distributed microeconomic flow control technique that models the network as competitive markets. In these markets, switches price their link bandwidth based on supply and demand, and users purchase bandwidth so as to maximize their individual quality of service (QoS). This yields a decentralized flow control method that provides a Pareto optimal bandwidth distribution and high utilization (over 90% in simulation results). Discussions about stability and the Pareto optimal distribution are given, as well as simulation results using actual MPEG-compressed video traffic.

An architecture for adaptive QoS and its application to multimedia systems design

We describe a prototype implementation of a distributed multimedia system that generalizes the concept of QoS to all layers of its software architecture. Each layer deals with QoS at its appropriate level of abstraction using a generic API for communicating QoS parameters and values to layers above and below. The aggregation of these parameters and values is called a service contract. This architecture provides a hierarchical framework to design adaptive multimedia systems. Furthermore, the API allows for reporting of contract violations as well as dynamic renegotiation of the contract terms. A proof-of-concept multimedia system was built to evaluate the proposed architecture. Key components of this system are: a graphical user interface that dynamically requests the quality expected by the user to lower level components, a dynamic network service that efficiently matches network resources to user requirements and a processor scheduler which schedules tasks according to their execution requirements. Our experience with this system showed that the proposed architecture is an efficient framework for building adaptive multimedia systems.

ORBIT Measurements framework and library (OML): motivations, implementation and features

In this paper we present ORBIT measurement framework and library (OML), which is a distributed software framework enabling real-time collection of data in a large distributed environment. The success of a multiuser distributed testbed facility depends largely on the ease of use, remote access as well as on the ease of collecting useful measurements from experimental runs. OML provides a flexible and dynamic way in which data is collected and made available for realtime access to the experimenters. Application programmers can use simple interfaces provided to transfer measurements and other performance data to a central repository. This paper focuses on the motivation, requirements, design, implementation and real world usage of OML that is designed to provide a scalable, controllable and easy to use mechanism for experimenters to collect useful results from the experiments conducted on the ORBIT testbed.

A dynamic quality of service framework for video in broadband networks

A dynamic framework for QoS control of video in distributed multimedia applications is presented. The framework allows flexible and efficient video delivery with application-level QoS support. Key components of the framework are client QoS renegotiation, server source rate control, and dynamic bandwidth allocation. The coordinated functionality of these distributed components provides soft QoS to adaptive applications. A proof-of-concept prototype of a video browser with user-level control of soft QoS is implemented within the proposed framework. The implementation uses a distributed software architecture that represents soft QoS requirements by software objects called service contracts. These objects are exchanged among servers, network nodes, and clients to achieve distributed soft QoS control. Experiences with the prototype and its performance are discussed.

Teleconferencing eye contract using a virtual camera

To preserve eye contact in teleconferencing both the camera and the monitor need to be positioned on the same optical axis which, in practice, is usually not possible. We propose a method to construct the view from a virtual coaxial centered camera given two cameras mounted on either side of the monitor. Stereoscopic analysis of the two camera views provides a partial three-dimensional description of the scene. With this information it is possible to “rotate” one of the views to obtain a centered coaxial view that preserves eye contact.

ATM connection and traffic management schemes for multimedia internetworking

The rapid advances being made in microprocessor technology have stimulated significant interest in distributed multimedia applications supported by high-speed networks. Examples of distributed multimedia applications include multimedia database retrieval, distributed multimedia documents, and video mail. Due to the large amount of multimedia traffic for audio/visual applications, these applications require high speed networks to retrieve data in real time, instead of huge local disk storage

Source-location privacy for networks of energy-constrained sensors

Wireless sensor networks are currently being investigated for ubiquitous computing applications. Privacy is a critical issue for these networks as adversaries may be able to eavesdrop or observe the presence of sensor data to infer information that was not intended to be revealed. The devices that constitute sensor networks are low-powered, compute-constrained devices. Any privacy solution should carefully consider the tradeoffs between supporting location-privacy and energy consumption. We explore two main classes of privacy issues: content privacy and originator location privacy. Content privacy can be maintained through conventional cryptographic methods that provide data confidentiality. We briefly discuss system design techniques that are needed to prevent an adversary from correlating observations from multiple messages to infer the content of encrypted sensor readings. We then examine the issue of protecting the originating sensors location by studying several multihop routing mechanisms for ad hoc networks. We focus our discussion on three classes of routing protocols: the class of the shortest path routing protocols, the class offloading protocols, and a hybrid class of routing.

Measurement Architectures for Network Experiments with Disconnected Mobile Nodes

Networking researchers using testbeds containing mobile nodes face the problem of measurement collection from partially disconnected nodes. We solve this problem efficiently by adding a proxy server to the Orbit Measurement Library (OML) to transparently buffer measurements on disconnected nodes, and we give results showing our solution in action. We then add a flexible filtering and feedback mechanism on the server that enables a tailored hierarchy of measurement collection servers throughout the network, live context-based steering of experiment behaviour, and live context-based control of the measurement collection process itself.