1. A method comprising: at a service controller for a network comprising a plurality of service nodes each configured to apply a service function to traffic that passes through the respective service node, defining a service chain identifying a set of service functions and an order in which they are applied; receiving an indication that the service chain has been instantiated at a classifier; and creating a unique service path for the service chain, wherein the unique service path includes the service chain and the classifier at which the service chain is instantiated.