1. A network abstraction gateway (NAG) comprising: at least one abstracted network interface (AN-I) for connectivity with at least one abstracted network (AN) wherein a user has an abstracted endpoint (AE) having a first identity in said abstracted network (AN); at least one communication system interface (CS-I) for connectivity with at least one user's communication system (CS), said communication system interface (CS-I) exposing abstracted endpoint behavior via a second identity in said user's communication system (CS); means (REG) adapted for registering a one-to-one relationship between said first identity and said second identity;means for extracting behavior of said abstracted endpoint (AE), comprising communication features and/or states of said abstracted endpoint (AE); and endpoint abstraction means (AM) adapted for abstracting said abstracted endpoint (AE) in said user's communication system (CS) via an endpoint abstraction (EA) using said second identity, said endpoint abstraction (EA) being responsive to behavior of said abstracted endpoint (AE), being adapted to implement at least one feature and/or state of said user's communication system (CS), and being adapted to bi-directionally map said behavior of said abstracted endpoint (AE) with features and/or states of said user's communication system (CS) via a protocol supported by said user's communication system (CS).
8. A network abstraction gateway (NAG) according to claim 1 , wherein said protocol supported by said user's communication system (CS) is: the Session Initiation Protocol or SIP; the eXtensible Messaging and Presence Protocol or XMPP; the Skype protocol; the Time-Division Multiplexing or TDM protocol; a proprietary Time-Division Multiplexing or TDM protocol; or the Bluetooth protocol.