scope:

The purpose of this military standard (MIL-STD) is to provide a baseline for a gateway between tactical networks and strategic networks. The tactical networks are digital networks based on Tri-Service Tactical Communications (TRI-TAC) specifications. The strategic networks are digital networks based on Integrated Services Digital Network (ISDN) standards. This MIL-STD addresses the requirements for transmission of voice and data, through the gateway, between tactical and strategic circuit-switched networks. The requirements are specifically for the gateway and do not address requirements for a gateway switch. These requirements further presume that a call is always set up as a dial-up, circuit-switched call and that it progresses such that an inband, end-to-end, encrypted phase can be established with the New Terminal to support secure voice or secure data transmissions. This MIL-STD is a further development of sections 4.1.3 and 5.2.4 of the following planning standard: MIL-STD-187-700, Interoperability and Performance Standards for the Defense Information System.

This MIL-STD applies to interfaces between digital communications systems only. Analog interfaces are covered in Joint Interoperability and Engineering Organization (JIEO) Technical Interface Specification (TIS) 9115.

This MIL-STD has three objectives:

a. To achieve interoperability between strategic (ISDN) and tactical (TRI-TAC) digital circuit-switched networks for voice and data.

b. To achieve cost-effective interoperability and performance across the interface by referencing specific subsets of military and commercial standards.

c. To provide the following gateway capabilities:

1. Five levels of precedence and preemption.

2. Common-channel-signaling message conversion.

3. Choice of rate adaption or transcoding for voice algorithm conversion.

4. Direct digital interfacing that preserves bit-count integrity (BCI).

5. Support of end-to-end transmission and reception of secure voice and secure data.

This MIL-STD is based on the Defense Information System (DIS) framework (see 4.1, Figure 1) described below.

a. The DIS concept provides for an evolutionary integration of existing and future Department of Defense (DOD) computer and telephone communications systems. DOD Services and Agencies adopted the DIS framework as a guide for developing MIL-STD-187-700. The DIS framework provides efficient, end-to-end, integrated services for information sources, sinks, and processors. Integrated services provide for voice, message, graphic, and imagery transfer across a single network interface. By definition, the DIS framework includes all components necessary to achieve interoperability between and among DOD users.

b. The DIS framework consists of three major sections demarcated by reference points A and B. Users may access the DIS through subscriber network elements, such as source, sink, or processor terminal equipment. These terminal equipment include telephones, facsimile machines, and other data terminal equipment (DTE). For the information source, sink, and processor elements to be interoperable, all seven layers of the International Standards Organization (ISO) Open Systems Interconnection (OSI) Reference Model must be interoperable.

c. DTEs exchange information through information-transfer utilities. Information-transfer utilities are composed of local-network elements, wide-network elements, and their respective interoperability reference points. DOD Services and Agencies provide fixed-plant, local-network elements to support strategic users and base operations. They also provide tactical local-network elements to support garrison operations and access to wide-network elements, as well as tactical-network elements to support deployed combat forces. The Defense Information Systems Agency (DISA) provides wide-network elements to interconnect geographically separated local-network elements. The wide-network elements include the Defense Communications System (DCS) and public switched telephone networks (PSTN). Since the local - and wide-network elements and interoperability reference points in the information-transfer utilities represent the telecommunications portion of DIS, their functionality is limited to the lower three layers of the OSI Reference Model.

d. Advances in computer and telephone communications technology allow multiple services to be provided by a single network, such as ISDN. Wherever applicable, the DIS framework allows the adoption of commercial standards for ISDN. Within the DIS framework, circuit-switched voice and data services are based on TRI-TAC specifications for tactical systems and ISDN commercial standards for strategic systems.