definition is as follows sn_id uniquely identifies a given user who may have many particular service numbers the sn_id is an abstract number independent of any specific service network technology and such a user id can re use any existing service number e g msisdn ip address or any new defined number in future whatever number is used for sn_id it must be capable of uniquely identifying one user from another referring now to fig2 the system architecture 100 of fig1 requires two tables a standard sn records table 24 and an availability mapping table amt 26 in the standard sn records table 24 each user is identified by a sn number 28 and user may have several allowable services in the sn system 100 and all of those services are ranked in a service preference list 30 the availability mapping table 26 is the essential component for a dynamic sn service with mobility awareness and it is defined by three parts an activation flag 32 a service table 34 and an access network an table 36 the activation flag 32 is used to indicate whether the dynamic sn service has been activated or not the service table 34 includes the.