*** NOTE: DIETS (and the resources at this site) was the initial prototype of a project that has since moved. The project lives on as the "ISSI Test Tools (ITT)" component of the P25 Wireline Project on Java.net. For the current and maintained resources related to this effort please go to: p25-wireline.dev.java.net ***


NIST and NTIA’s Institute for Telecommunications Sciences (ITS) are working with DHS’s SAFECOM Program to support the emergency response community and industry in their effort to accelerate the development of Project 25 (P25) standards for interoperable communications.

One of the the keys to achieving near-term interoperability of P25 Radios is to bridge between potentially non-interoperable RF systems using standard IP-based Protocols. In P25, this bridge is referred to as the Inter-RF Sub-System Interface (ISSI). The ISSI suite comprises protocols that are built on top of Session Initiation Protocol (SIP) for call control signaling and Real-Time Transport Protocol (RTP) to support Push to Talk (PTT).

NIST's Advanced Network Technologies Division is supporting Project 25 by developing tools and technologies for testing and measuring ISSI equipment and infrastructure. Such tools include the Department of Commerce ISSI Evaluation and Test System (DIETS) which serves as an ISSI reference implementation and an ISSI test and evaluation framework.


  • NTIA / Institute for Telecommunications Sciences (ITS)
  • NIST / Office of Law Enforcement Standards (OLES)
  • DHS SAFECOMM Program
  • Telecommunications Industry Association (TIA) Project 25
  • Association of Public-Safety Communications Officials (APCO) International
  • P25 vendor community


  • M. Ranganathan, NIST/ANTD
  • Nie Pin NIST/ANTD
  • Doug Montgomery, NIST/ANTD
  • Kameron Behnam, NTIA/ITS
  • D.J. Atkinson, NTIA/ITS


  • Dereck Orr, NIST/OLES

    Ex Team Members

  • Steve Quirolgico, NIST/Computer Security Division

    Questions or comments should be sent to xproj-p25-issi-te@antd.nist.gov