Method for enabling server allocation in an Internet Protocol Multimedia Subsystem, IMS, based Multimedia over Internet Protocol, IP, network, including the following steps: - receiving by a Serving Call Session Control Function, S-CSCF, server (4.1, 4.2, 4.3) of the network registration data, upon registration of said subscriber in said network, - receiving by the S-CSCF server (4.1, 4.2, 4.3) subscription data upon registration of said subscriber in said network, the registration data and the subscription data together forming subscriber data, - transmitting, by the S-CSCF server (4.1, 4.2, 4.3), information representative of the subscriber data, including one of said subscriber data or a storage address where the subscriber data can be obtained, needed in the S-CSCF server (4.1, 4.2, 4.3) for originating session establishment from the subscriber to a Proxy Call Session Control Function, P-CSCF, server (2.1, 2.2, 2.3) for storing the information representative of the subscriber data, including one of said subscriber data or a storage address where the subscriber data can be obtained, in a memory by the P-CSCF server (2.1, 2.2, 2.3) and - transmitting, by the S-CSCF server (4.1, 4.2, 4.3), information representative of the subscriber data, including one of said subscriber data or a storage address where the subscriber data can be obtained, needed in the S-CSCF server (4.1, 4.2, 4.3) for originating or terminating session establishment from c.q. towards the subscriber to a Home Subscriber Server, HSS (6.1, 6.2), for storing the information representative of the subscriber data, including one of said subscriber data or a storage address where the subscriber data can be obtained, in a memory by the HSS (6.1, 6.2), - transmitting, by the S-CSCF server (4.1, 4.2, 4.3), a S-CSCF group address to the P-CSCF server (2.1, 2.2, 2.3) and to the HSS (6.1, 6.2), respectively, said S-CSCF group address being representative of a group of S-CSCF servers, the S-CSCF server (4.1, 4.2, 4.3) being included in said group of S-CSCF servers,- receiving by the Proxy Call Session Control Function, P-CSCF, server (2.1, 2.2, 2.3) a multimedia service request, being a session initiation message for initiating a communication session or a non-session related multimedia service transaction, - selecting, by the P-CSCF server (2.1, 2.2, 2.3), a Serving Call Session Control Function, S-CSCF, server (4.1, 4.2, 4.3) on the basis of the S-CSCF group address, and - including, by the P-CSCF server (2.1, 2.2, 2.3), information representative of the subscriber data, including one of said subscriber data or a storage address where the subscriber data can be obtained, said subscriber data being needed in the selected S-CSCF server (4.1, 4.2, 4.3) for originating session establishment from the subscriber, in the multimedia service request, and transmitting said multimedia service request to the selected S-CSCF server (4.1, 4.2, 4.3). - receiving by a Serving Call Session Control Function, S-CSCF, server (4.1, 4.2, 4.3) of the network registration data, upon registration of said subscriber in said network, - receiving by the S-CSCF server (4.1, 4.2, 4.3) subscription data upon registration of said subscriber in said network, the registration data and the subscription data together forming subscriber data, - transmitting, by the S-CSCF server (4.1, 4.2, 4.3), information representative of the subscriber data, including one of said subscriber data or a storage address where the subscriber data can be obtained, needed in the S-CSCF server (4.1, 4.2, 4.3) for originating session establishment from the subscriber to a Proxy Call Session Control Function, P-CSCF, server (2.1, 2.2, 2.3) for storing the information representative of the subscriber data, including one of said subscriber data or a storage address where the subscriber data can be obtained, in a memory by the P-CSCF server (2.1, 2.2, 2.3) and - transmitting, by the S-CSCF server (4.1, 4.2, 4.3), information representative of the subscriber data, including one of said subscriber data or a storage address where the subscriber data can be obtained, needed in the S-CSCF server (4.1, 4.2, 4.3) for originating or terminating session establishment from c.q. towards the subscriber to a Home Subscriber Server, HSS (6.1, 6.2), for storing the information representative of the subscriber data, including one of said subscriber data or a storage address where the subscriber data can be obtained, in a memory by the HSS (6.1, 6.2), - transmitting, by the S-CSCF server (4.1, 4.2, 4.3), a S-CSCF group address to the P-CSCF server (2.1, 2.2, 2.3) and to the HSS (6.1, 6.2), respectively, said S-CSCF group address being representative of a group of S-CSCF servers, the S-CSCF server (4.1, 4.2, 4.3) being included in said group of S-CSCF servers,- receiving by the Proxy Call Session Control Function, P-CSCF, server (2.1, 2.2, 2.3) a multimedia service request, being a session initiation message for initiating a communication session or a non-session related multimedia service transaction, - selecting, by the P-CSCF server (2.1, 2.2, 2.3), a Serving Call Session Control Function, S-CSCF, server (4.1, 4.2, 4.3) on the basis of the S-CSCF group address, and - including, by the P-CSCF server (2.1, 2.2, 2.3), information representative of the subscriber data, including one of said subscriber data or a storage address where the subscriber data can be obtained, said subscriber data being needed in the selected S-CSCF server (4.1, 4.2, 4.3) for originating session establishment from the subscriber, in the multimedia service request, and transmitting said multimedia service request to the selected S-CSCF server (4.1, 4.2, 4.3).