The article first provides a list of terms and definitions used as the basis for the article. The terms defined are IP (Internet Protocol) telephony; LMR (land mobile radio) IP trunking systems; Project 25 Inter RF Subsystem Interface (P25 ISSI); radio over IP; radio-over-IP bridging; VoIP (voice over IP); and VoIP telephony. The article next presents some basic guidelines on protocol alternatives, information that is useful for comparison purposes. After presenting definitions and basic guidelines on protocol alternatives, the article makes some “apples-to-apples” comparisons of the options. This discussion addresses a comparison of telephony and two-way LMR services and a comparison of radio over IP and LMR IP trunking. The article then turns to a discussion of considerations for decisionmaking about which alternatives to choose. The article notes that different agencies have their distinctive requirements, may operate on bands of differing frequencies, and/or be at different points in the system replacement cycle. In addition, solutions are increasingly likely to involve connections across two or more systems. In the latter instance, technology is advancing to assist in making these connections. The relevant technologies are described in this section. The article concludes with a description of how to connect to LMR IP trunking systems. The primary methods of connection are network to network, a console operator patch, site links, air interface, and radio wireline gateway. 2 tables and 2 figures