08.03.15 - 11.03.15, Seminar 15112

Network Calculus

Diese Seminarbeschreibung wurde vor dem Seminar auf unseren Webseiten veröffentlicht und bei der Einladung zum Seminar verwendet.

Motivation

The network calculus has established as a versatile methodology for the queueing analysis of resource sharing based systems. Its prospect is that it can deal with problems that are fundamentally hard for alternative methodologies, based on the fact that it works with bounds rather than striving for exact solutions. The high modelling power of the network calculus has been transposed into several important applications for network engineering problems, traditionally in the Internet’s Quality of Service proposals IntServ and DiffServ, and more recently in diverse environments such as wireless sensor networks, switched Ethernets, Systems-on-Chip, as well as smart grids.

The goal of this Dagstuhl seminar is to gather the deterministic and stochastic network calculus community, to discuss recent research activities, to identify future research questions, and to strengthen cooperation. Open questions and challenges that will be topics of this Dagstuhl seminar arise in the following areas:

  • Network topology: A remarkable quality of the network calculus is that it includes a variety of systems that can be composed to arbitrary network topologies. Various analytical as well as numerical approaches have been explored to analyze different types of topologies, such as line topologies or feed-forward networks. The goal of this seminar is to identify relevant classes of topologies, their defining properties, and corresponding methods.
  • Parallel systems: The area of performance evaluation of parallel systems has recently become increasingly important due to the prevalence of modern parallel computational models. It is thus a great opportunity for the network calculus community to develop new models and methods which can enable a fundamental and broad understanding of the performance of parallel systems.
  • Wireless systems: For the analysis of wireless networks, a question of interest is how the stochastic properties of wireless channels impact delay and backlog performance. The usual statistical models for radio signals in a propagation environment do not lend themselves easily to a queueing model. Promising methods that will be elaborated in the seminar are effective capacities and a recent network calculus of fading channels.
  • Flow transformations: A great challenge of existing methodologies for queueing analysis is to deal with flow transformations, which occur when the flows’ data is altered inside the network, e.g., in case of a video transcoder. While some progress for specific scaling elements has been made in the last few years, there are still many open issues. The promise of this topic is high as it widens the modelling scope of the network calculus dramatically
  • Lower bounds and tightness of bounds: Based on the ability to solve some fundamentally hard queueing problems, the stochastic network calculus is regarded as a valuable alternative to the classical queueing theory. The derivation of performance bounds in the stochastic network calculus, e.g., for backlog, and delay, frequently exploits well known tail estimates, such as Chernoff bound and others. The tightness of these bounds and alternative more accurate models and techniques will be a topic of the seminar.
  • Finite buffers: A typical and convenient assumption in network calculus is that queueing buffers are infinite. It is of significant interest to re-consider this fundamental assumption and develop new models which can be more suitable for finite buffer systems.