The Network Configuration Protocol (NETCONF) defines ways to read and edit configuration data from a NETCONF server. In some cases@ part of this data may not be set by the NETCONF client@ but rather a default value known to the server is used instead. In many situations the NETCONF client has a priori knowledge about default data@ so the NETCONF server does not need to save it in a NETCONF configuration datastore or send it to the client in a retrieval operation reply. In other situations the NETCONF client will need this data from the server. Not all server implementations treat this default data the same way. This document defines a capability-based extension to the NETCONF protocol that allows the NETCONF client to identify how defaults are processed by the server@ and also defines new mechanisms for client control of server processing of default data.