Cisco Systems, Inc. Cisco Systems, Inc. Cisco Systems, Inc. Nokia Huawei This document defines a mechanism to allow clients, using NETCONF or RESTCONF, to configure and select YANG schema for interactions with a server. This functionality can help servers support clients using older revisions of YANG modules even if later revisions contain non- backwards-compatible changes. It can also be used to allow clients to select between YANG schema defined by different organizations. This draft provides a solution to YANG versioning requirements 3.1 and 3.2.