A Study on Network Performance Metrics and their Composition

Research backbone networks like GÉANT2 and the National Research and Education Networks are used by a variety of scientists and research projects. These users and the network engineers operating the networks would like to get access to network performance metrics to optimise their use of the network and to troubleshoot performance degradations, when they happen. A variety of tools for performing network measurements already exist, and the perfSONAR architecture developed within the Joint Research Activity 1 (JRA1) of GÉANT2 aims at integrating them in a coherent framework. However, a harmonised definition of which metrics are mostly interesting and how measurements must be carried out is still lacking. In this paper we suggest the set of elementary metrics which are more relevant, along with indication about how to post process (or “transform”, or “compose”) them in order to obtain derived summary values that can quickly and intuitively give an indication of network performance. Methods to perform the composition are presented, together with constraints which have to be taken into account to get accurate results. In particular, delay measurements are the most delicate ones to compose. We carried out a series of experiments for proofing the validity of composition of delay metrics, and we briefly present some preliminary results.