Trajectory sampling for direct traffic observation

Traffic measurement is a critical component for the control and engineering of communication networks. We argue that traffic measurement should make i t possible to obtain the spatial flow of traffic through the domain, i.e., the paths followed by packets between any ingress and egress point of the d omain. Most resource allocation and capacity planning tasks can benefit fro m such information. Also, traffic measurements should be obtained without a routing model and without knowledge of network state. This allows the traf fic measurement process to be resilient to network failures and state uncer tainty. We propose a method that allows the direct inference of traffic flo ws through a domain by observing the trajectories of a subset of all packet s traversing the network. The key advantages of the method are that 1) it d oes not rely on routing state; 2) its implementation cost is small; and 3) the measurement reporting traffic is modest and can be controlled precisely . The key idea of the method is to sample packets based on a hash function computed over the packet content. Using the same hash function will yield t he same sample set of packets in the entire domain, and enables us to recon struct packet trajectories.