A Framework-Based Approach to the Development of Network-Aware Applications

Bolliger, J. and Gross, T.

Abstract

Modern networks provide a QoS (quality of service) model to go beyond best-effort services, but current QoS models are oriented towards low-level network parameters (e.g., bandwidth, latency, jitter). Application developers, on the other hand, are interested in quality models that are meaningful to the end-user and therefore struggle to bridge the gap between network and application QoS models. Examples of application quality models are response time, predictability, or a budget (for transmission costs).

Applications that can deal with changes in the network environment are called {\em network-aware}. A network-aware application attempts to adjust its resource demands in response to network performance variations. This paper presents a framework-based approach to the construction of network-aware programs. At the core of the framework is a feedback loop that controls the adjustment of the application to network properties. The framework provides the skeleton to address two fundamental challenges for the construction of network-aware applications: (i) how to find out about dynamic changes in network service quality and (ii) how to map application-centric quality measures (e.g., predictability) to network-centric quality measures (e.g., QoS models that focus on bandwidth or latency).

Our preliminary experience with a prototype network-aware image re\-trie\-val system demonstrates the feasibility of our approach. The prototype illustrates that there is more to network-awareness than just taking network resources and protocols into account and raises questions that need to be addressed (from a software engineering point of view) to make a general approach to network-aware applications useful.