Traffic Matrix Reloaded: Impact of Routing Changes

A traffic matrix represents the load from each ingress point to each egress point in an IP network. Although networks are engineered to tolerate some variation in the traffic matrix, large changes can lead to congested links and poor performance. The variations in the traffic matrix are caused by statistical fluctuations in the traffic entering the network and shifts in where the traffic leaves the network. For an accurate view of how the traffic matrix evolves over time, they combine fine-grained traffic measurements with a continuous view of routing, including changes in the egress points. Analyzing seven months of data from eight vantage points in a large Internet Service Provider (ISP) network, they show that routing changes are responsible for the majority of the large traffic variations.