In this paper, we study traffic demands in an IP bacbkone, identify the routes used by these demands, and evaluate traffic granularity levels that are attractive for improving the poor load balancing that our study reveals. The data used in this study was collected at a major POP in a commercial Tier-1 IP backbone. In the first part of this paper we ask two questions. What is the traffic demand between a pair of POPs in the backbone? How stable is this demand? We develop a methodology that combines packet-level traces from access links in the POP and BGP routing information to build components of POP-to-POP traffic matrices. Our analysis shows that the geographic spread of traffic across egress POPs is far from uniform. In addition, we find that the time of day behaviors for different POPs and different access links also exhibit a high degree of heterogeneity. In the second part of this work, we examine commercial routing practices to assess how these demands are routed through the ba...