The integrity@ confidentiality@ and availability of Emergency Telecommunication Service (ETS) in a multi-provider Next Generation Network (NGN) environment will depend on the security of each individual network involved in an end-to-end communication. To allow network provided security of end-to-end ETS communications in a multiprovider environment@ intra-network domain and inter-network domain security requirements for ETS protection are needed. This ATIS standard provides minimum security requirements for the security protection of ETS in a multi-provider NGN environment. The scope of this ATIS standard is common (i.e.@ requirements that are independent of network type or technology) and core network security requirements in the context of supporting ETS in a multi-provider NGN environment. The scope of the security requirements includes integrity@ confidentiality@ and availability protection for ETS communications within a network and across network boundaries (i.e.@ between different network domains). Purpose The purpose of this ATIS standard is to provide a minimum set of security requirements that can be used to facilitate the security protection of ETS communications across directly or indirectly interconnected networks. The requirements in this standard are intended to protect ETS applications and resources against security threats@ including protection of the network infrastructure supporting the ETS applications. Another purpose of this standard is to promote interoperability in a multi-network@ multi-service provider@ and multi-vendor environment.