Path-agnostic network measurements using distributed sketches

To make meaningful decisions about a network, network-wide and consistent measurement of the sizes of all flows is essential. Existing measurement efforts assume that the path of a flow remains the same throughout, while in practice, it changes due to load balancing, network updates etc. It is also assumed that the controller is aware of path-changes, which may not be true always due to activities confined entirely to the data plane. To approximately measure the sizes of all flows, in a path-agnostic manner, we propose that flow ids may be stored, and corresponding measurements stored in sketches, and the memory available may be split between both. Moreover, measurement sketches may be distributed across a network for efficient resource usage, on a subset of switches, called the contributing switches, such that a packet gets counted only once per path, instead of multiple times, as is currently done. When the counters of a sketch corresponding to a flow header are full, the counters in the next contributing switch in the path of the packet may begin counting the flow. We propose a switch algorithm that stores per-epoch measurements and evicts and resets them periodically and lazily. The controller adds the flow sizes estimated from individual sketches and flow identifiers of an epoch, to get the total flow sizes. We implement and evaluate the algorithm on a simulated data center network, with realistic workloads and demonstrate its feasibility.