A method of processing data in a telecommunications network, the network comprising: a cluster of network nodes responsible for conducting registration procedures for subscriber devices and/or processing routing data relating to communication sessions conducted in the network; and a shared registration data store comprising registration data for a plurality of subscriber devices, the shared registration data store being accessible by each of the network nodes of the cluster of network nodes, the method comprising, at a first network node of the cluster of network nodes: receiving a communication session setup request requesting the setup of a communication session with a subscriber device in the plurality of subscriber devices; retrieving (3b, 3c) registration data relating to the subscriber device from the shared registration data store; and routing the communication session setup request according to the retrieved registration data, the retrieved registration data relating to the subscriber device having been previously stored in the shared registration data store by a second network node of the cluster of network nodes in relation to a registration procedure conducted for the subscriber device by the second network node, the second network node being a different network node than the first network node in the cluster of network nodes, characterised in that: the registration data relating to the subscriber device is retrieved from the shared registration data store by the said first network node which is different from the second network node in the cluster of network nodes in response to receipt of the communication session setup request at the said first network node. a cluster of network nodes responsible for conducting registration procedures for subscriber devices and/or processing routing data relating to communication sessions conducted in the network; and a shared registration data store comprising registration data for a plurality of subscriber devices, the shared registration data store being accessible by each of the network nodes of the cluster of network nodes, the method comprising, at a first network node of the cluster of network nodes: receiving a communication session setup request requesting the setup of a communication session with a subscriber device in the plurality of subscriber devices; retrieving (3b, 3c) registration data relating to the subscriber device from the shared registration data store; and routing the communication session setup request according to the retrieved registration data, the retrieved registration data relating to the subscriber device having been previously stored in the shared registration data store by a second network node of the cluster of network nodes in relation to a registration procedure conducted for the subscriber device by the second network node, the second network node being a different network node than the first network node in the cluster of network nodes, characterised in that: the registration data relating to the subscriber device is retrieved from the shared registration data store by the said first network node which is different from the second network node in the cluster of network nodes in response to receipt of the communication session setup request at the said first network node. receiving a communication session setup request requesting the setup of a communication session with a subscriber device in the plurality of subscriber devices; retrieving (3b, 3c) registration data relating to the subscriber device from the shared registration data store; and routing the communication session setup request according to the retrieved registration data, the retrieved registration data relating to the subscriber device having been previously stored in the shared registration data store by a second network node of the cluster of network nodes in relation to a registration procedure conducted for the subscriber device by the second network node, the second network node being a different network node than the first network node in the cluster of network nodes, characterised in that: the registration data relating to the subscriber device is retrieved from the shared registration data store by the said first network node which is different from the second network node in the cluster of network nodes in response to receipt of the communication session setup request at the said first network node.