This Recommendation provides guidance, principles and requirements for addressing reference points located at subscribers' premises, servers allowing communications between terminals, applications and persons in B-ISDN networks. This revision of E.191 was required in order to reflect the fact that B-ISDN addressing has also incorporated the use of non-E.164 ATM End System Addresses (AESAs) to be recognized in ATM Service Providers (ASP) networks. This Recommendation proposes that ASPs use the ITU-IND AESA as the preferred method of B-ISDN addressing. Native E.164 and E.164 AESAs will continue to be supported. It is also recognized that other AESA formats are assigned and in use by ASPs.