QoS estimators for client-side dynamic server selection: limitations and keys

The traditional way to cope with the increasing number of users in distributed information services is to use server replication, but additional and complementary strategies have been proposed in the last few years, in this paper, we evaluate those server selection strategies in which, by means of a packet burst sent from the client side, some QoS parameters such as delay, available bandwidth and packet loss can be estimated. In particular, our study is focused on the estimation of available bandwidth, proposing a two-step algorithm to measure it in the path to each server. Ethernet, ISDN and ADSL technologies have been used, and different scenarios and packet conditions have been tested in order to identify the limitations and design keys of bandwidth estimation methods.