Integrated Services Digital Network (ISDN) – Layer 3 Signaling Specification for Circuit Switched Bearer Service for Digital Subscriber Signaling System Number 1 (DSS1)
|Publication Date:||1 June 2014|
Scope and purpose
This standard specifies the procedures for the establishing, maintaining, and clearing of network connections at the Integrated Services Digital Network (ISDN) user-network interface for support of circuitswitched calls. These procedures are defined in terms of messages exchanged over the D-channel. The functions and procedures of this protocol, and the relationship with other layers, are described in general terms in ITU-T Recommendation Q.930, ISDN User-Network Interface: Layer 3 General Aspects.
One of the key characteristics of an ISDN is the use of an internationally standardized set of messages and procedures as a layer 3 protocol for control of connections at interfaces between users and the ISDN ("user-network interfaces").
This document defines the messages and procedures employed for control of circuit-switched connections at user-network interfaces. These messages and procedures are applicable to both basic-rate and primary-rate interfaces. They are generally aligned with those defined in ITU-T Recommendation Q.931, ISDN User-Network Interface: Layer 3 Specification.
Packet-mode connections and supplementary services are not addressed in this standard.
Messages and procedures for the control of packet-mode connections and supplementary services are defined in other American National Standards.