Specifications include, but are not limited to: 1. The network between the PSAP and the ESInet will be private or a virtual private network (VPN) that supports, at a minimum, Transmission Control Protocol (TCP)/IP, UDP, and RTP. 2. It will have scalable bandwidth to support new enhanced services. Some existing network infrastructure, like a legacy Frame Relay network, is not scalable enough for an ESInet, and may present other problems. Other legacy technologies like Asynchronous Transfer Mode (ATM) are scalable, but present other issues. Metro Ethernet or Multi-Protocol Label Switching (MPLS) are preferred over ATM for this reason. NENA-INF-016 Emergency Services IP Network Design (ESIND) Information Document describes multiple options to choose from for building ESInets that support scalable bandwidth, and provides details on other advantages and disadvantages for each option. All of this should be considered when developing the requirements for an RFP to procure ESInet infrastructure and NG 9-1-1 Core Services.