The migration feature of NFSv4 provides for moving responsibility for a single filesystem from one server to another, without disruption to clients. Recent implementation experience has shown problems in the existing specification for this feature. This document discusses the issues which have arisen and explores the options available for curing the issues. It also explains the choices made regarding updating the NFSv4.0 specification and those to be made with regard to the NFSv4.1 specification, in order to properly address migration.