According to an aspect, there is provided a method of operating a terminal device, the method comprising maintaining one or more indices and a mapping between the one or more indices and respective network identifiers, each network identifier identifying a network and/or a network node; and in communications between the terminal device and a first network in which a particular network and/or a particular network node is to be identified, using the index associated with the particular network and/or the particular network node to identify the particular network and/or the particular network node. Methods of operating network nodes in a network are also provided.