Understanding TraÆc Dynamics at a Backbone POP

Spatial and temporal information about traÆc dynamics is central to the design of e ective traÆc engineering practices for IP backbones. In this paper we study backbone traÆc dynamics using data collected at a major POP on a tier-1 IP backbone. 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 traÆc matrices. Our results show that there is wide disparity in the volume of traÆc headed towards di erent egress POPs. At the same time, we nd that current routing practices in the backbone tend to constrain traÆc between ingress-egress POP pairs to a small number of paths. As a result, there is a wide variation in the utilization level of links in the backbone. Frequent capacity upgrades of the heavily used links are expensive; the need for such upgrades can be reduced by designing load balancing policies that will route more traÆc over less utilized links. We identify traÆc aggregates based on destination address pre xes and nd that this set of criteria isolates a few aggregates that account for an overwhelmingly large portion of inter-POP traÆc. We also demonstrate that these aggregates exhibit stability throughout the day on per-hour time scales, and thus they form a natural basis for splitting traÆc over multiple paths in order to improve load balancing.