Paolo Scotton

Network infrastructure for massively distributed games

The popularity of hypertext documents led to the need for specific network infrastructure elements such as HTML caches, URL-based switches, web-server farms, and as a result created several new industries as companies rushed to fill that need. We contend that massive distributed games will have a similar impact on the Internet and will require similar dedicated support. This paper outlines some initial work on prototyping such support. Our approach is to combine highlevel game specific logic and low-level network awareness in a single network-based computation platform that we call a booster box.

Communication Architectures for Massive Multi-Player Games

Massive multi-player games are characterized by a large number of participating players. It is therefore essential that an appropriate communication architecture is deployed in order to support an ever growing number of players. Several such architectures have been proposed, including client-server and peer-to-peer architectures. In this paper, we propose a systematic method to assess the scalability of different architectures in order to identify the most appropriate one for specific game types. The model proposed is very general in that it covers centralized, distributed, and hybrid architectures and it is applied to the client-server, peer-to-peer and the newly introduced federated peer-to-peer architecture. Quantitative expressions that capture the effect of various game types are derived, and the trade-offs among the architectures are identified.

Techniques for integrating sensors into the enterprise network

Cheap programmable sensor devices are becoming commercially available. They offer the possibility of transforming existing enterprise applications and enabling entirely new ones. The merging of sensor networks into the enterprise network poses some distinct problems. In particular, information from theses devices must be obtained in a way which minimizes their energy use and must be aggregated and filtered before being sent to the application server to prevent it from being overwhelmed. We describe a range of complementary techniques for integrating sensors into an enterprise network. These comprise new architectural entities within the enterprise network — edge server — new means of sharing information within the enterprise network — messaging binning — and new protocols for extracting information from the sensor network — Messo.

Edge server software architecture for sensor applications

Edge servers perform computation on data in addition to that performed by the application server. Typically edge servers are deployed just in front of the application server and perform simple generic functions such as load balancing. With the increasing integration of network connected sensors into Internet based applications we foresee the need for the deployment of edge servers at the other end of the network, i.e. at the boundary with the external sensor network. These edge servers reduce the amount of data that has to be sent to the application server by filtering, summarizing and aggregating the sensor data. They are distinct from existing servers in both the location they run and the application-specific functions they perform. Both these differences influence their design. We describe our implementation of such an edge server.

Efficient frontier formulation for additive and restrictive metrics in hierarchical routing

In a hierarchical network, groups of nodes are represented by logical nodes for the purposes of simplifying routing. Each group has a set of ingress-egress nodes, and routing information is conveyed to the outside world in the form of a transition matrix that gives the cost of traversing the network between each ingress-egress node pair. In this paper, we present a minimal logical node representation that has sufficient descriptive power to enable path selection in support of connection admission control for services that have both path (restrictive) and link (additive) constraints. For example, the representation can be used to find a path that maximizes bandwidth subject to a delay constraint or minimizes delay subject to a bandwidth constraint. We present our solution in the form of a matrix whose elements are vectors, each of which specifies the efficient frontier of the solution space, and we specify an efficient procedure for constructing the efficient frontier. We present the least upper bound on the number of elements that must be present in the efficient frontier. We provide numerical examples that illustrate construction of the efficient frontier.

A quality-of-information-aware framework for data models in wireless sensor networks

Wireless sensor networks are used to monitor a given environment, such as indoor heating conditions or the micro-climate of glaciers. They offer a low-cost solution that provides a high data density. Usually the user of such a sensor network has a good idea of how, knowing the environment, the sensed values should behave. This idea can be expressed as a data model. Such models can be used to detect anomalies, compress data, or combine data from many inexpensive sensors to increase the quality of the measurements. This paper presents a framework to process arbitrary sensor-network data models. The framework can then be used to distribute the model processing into the wireless sensor network. Quality of information criteria are used to determine the performance of the models. A prototype of the framework is presented together with a comparison of two existing stochastic data model approaches for wireless sensor networks.

Topology aggregation for combined additive and restrictive metrics

In a hierarchical network, nodes are aggregated to groups for the purpose of simplifying routing. Each group has a set of ingress-egress nodes, and routing information is conveyed to the outside world in the form of a transition matrix (or other equivalent form) that gives the cost of traversing the network between each ingress-egress node pair. In this paper, we present a transition matrix that has enough descriptive power to support service requirements that have both restrictive (bandwidth) and additive (delay) constraints. We present a solution in the form of a matrix whose elements are functions that map requested bandwidth to minimum delay. These functions describe the efficient frontier of the solution space, and we specify a generic procedure for calculating the efficient frontier for various delay functions. The complexity of this procedure is given for a set of well-known delay functions that are of practical importance.

Toward scalable real-time messaging

Conventional messaging technologies have been designed for large transactional systems, making the prediction and calibration of their delay impractical. In this paper, we present a minimal messaging system, implemented in Java™, that is designed to enable the analysis, modeling, and calibration of the expected performance of these technologies. We describe the algorithms and protocols that underlie this messaging system, show how an analysis can be performed, and give the actual measured performance figures. We show that the system achieves a throughput of more than 100,000 messages per second with less than 120-millisecond maximum latency, in the test environment. At 10,000 messages per second, a maximum latency of 5 milliseconds is measured. The algorithms make use of lock-free data structures, which allow the throughput to scale on multi-core systems.

Efficient programmable middleboxes for scaling large distributed applications

A range of application classes is emerging in the Internet whose characteristics differ considerably from those of the point-to-point request/response protocols, which have dominated its recent past. Sensor applications, peer-to-peer systems, and massive multiplayer on-line games are multi-point applications that share both a need for the timely correlation of data generated by different participants in a session and a potentially unlimited number of session participants. We propose the use of middleboxes residing in the network to help in the scaling of these applications. As these emerging applications are not readily subject to standardization, we believe that a programmable model, in which a given middlebox can be instrumented to support various applications either simultaneously or over time, is desirable. We describe our work to date in building such a middlebox that makes use of hardware assists in its data path to maintain high performance.

A low complexity video subband coder for ATM

Abstract This paper discusses a low complexity, very good visual quality video subband coder fully compatible with ATM networks. The coder is designed to compress an incoming video signal bit-rate by a factor of 9–13 and it is applicable to ‘ Head & Shoulders ’ as well as ‘ Full Motion ’ sequences. Such results being obtainable in a 17 Mips calculation complexity environment allow the coder implementation on a conventional digital signal processor. The system exploits the characteristics of subband decomposed image through a ‘multiresolution’ quantization methodology. This new resource allocation technique enables the coder to be layered and variable bit-rate. These two properties are essential for optimal use of the coder on a fast packet switching network.