A method for establishing a multi-domain network slice in a telecommunications network, the telecommunications network being an internetwork of a first network domain and second network domain, in which the first network domain and second network domain are of different network types being one of an access network, backhaul network and a core network, the method comprising the steps of: a network node receiving a request from one of a first set of network nodes in the first network domain to establish a multi-domain network slice across the first and second network domains, the multi-domain network slice using a first network slice operating on one or more of the first set of network nodes of the first network domain and a second network slice operating on one or more of a second set of network nodes of the second network domain, wherein the request includes requirement data for the multi-domain network slice for one or more attributes; the method characterised by: the network node including a network slice database storing data on a plurality of network slices established in the first and second network domains; the network node receiving data indicating a change to the plurality of network slices established in the first and second network domains and, in response, updating the network slice database; the network node identifying the second network slice by: retrieving, from the network slice database, network slice capability data for the second network slice, the network slice capability data indicating the second network slice's capability for the one or more attributes, comparing the retrieved network slice capability data for the second network slice with the requirement data for the multi-domain network slice, and selecting the second network slice based on the comparison; and the network node responding to the request with an identifier for the second network slice. a network node receiving a request from one of a first set of network nodes in the first network domain to establish a multi-domain network slice across the first and second network domains, the multi-domain network slice using a first network slice operating on one or more of the first set of network nodes of the first network domain and a second network slice operating on one or more of a second set of network nodes of the second network domain, wherein the request includes requirement data for the multi-domain network slice for one or more attributes; the method characterised by: the network node including a network slice database storing data on a plurality of network slices established in the first and second network domains; the network node receiving data indicating a change to the plurality of network slices established in the first and second network domains and, in response, updating the network slice database; the network node identifying the second network slice by: retrieving, from the network slice database, network slice capability data for the second network slice, the network slice capability data indicating the second network slice's capability for the one or more attributes, comparing the retrieved network slice capability data for the second network slice with the requirement data for the multi-domain network slice, and selecting the second network slice based on the comparison; and the network node responding to the request with an identifier for the second network slice. the network node including a network slice database storing data on a plurality of network slices established in the first and second network domains; the network node receiving data indicating a change to the plurality of network slices established in the first and second network domains and, in response, updating the network slice database; the network node identifying the second network slice by: retrieving, from the network slice database, network slice capability data for the second network slice, the network slice capability data indicating the second network slice's capability for the one or more attributes, comparing the retrieved network slice capability data for the second network slice with the requirement data for the multi-domain network slice, and selecting the second network slice based on the comparison; and retrieving, from the network slice database, network slice capability data for the second network slice, the network slice capability data indicating the second network slice's capability for the one or more attributes, comparing the retrieved network slice capability data for the second network slice with the requirement data for the multi-domain network slice, and selecting the second network slice based on the comparison; and the network node responding to the request with an identifier for the second network slice.