US Patent 10021605 Non-interrupted handoff of real-time network-distributed services

A real-time service is distributed across multiple hosts, with different instances of the service running on the different hosts. Instances of a current (non-updated) version of a service run concurrently with instances of an updated version of the same service for some period of time. In order to smoothly handoff the handling of client requests so as to handle all packets, the different instances of the service evaluate one or more criteria that include a listed data timestamp of packets embodying the client requests. Use of objective criteria such as the listed data timestamp allow the different service instances to evaluate the criteria in a way that is consistent with the evaluations of the other instances, despite computer network-induced variability such as imperfect clock synchronization among hosts and variance in request delivery time.