The present invention relates to a session handling entity in a communication system, the session handling entity (S-CSCF) maintain a relationship between at least one public user identity, at least one private user identity and at least one contact address of a user of a communication system. Then receives from a subscription entity an indication of a correlation identity associated with the user, and stores the indication of the correlation identity as part of the relationship maintained by the maintaining means. When a session request of the user is received, determining the correlation identity for the user based on a contact address of the user included in the session request and the indication of a correlation identity associated with the user take place, and the correlation identity is included in the session request.