Network latency metrics for server proximity

This paper investigates network latency metrics in the context of the server proximity problem. Using a combination of experimentation and statistical analysis, we study the correlation among number of network and administrative system (AS) hops, and round-trip time (RRT). We ran experiments involving 601 Internet sites spanning 5 continents. Our results show reasonably strong AS hop-network hop correlations of up to 70%. We also observe an average RTT-number of hop correlation close to 50%, which represents a considerable improvement over what Crovella and Clark observed in 1995. Based on our results, we argue that, when choosing a single metric for network latency, RTT should be the metric of choice when trying to reduce clients´ perceived latency. However, hop counts are good indicators of network resource usage. Another factor that favors RTT is that it is the least expensive metric to measure