Integrated Services Digital Network (ISDN) – Signaling Specification for X.25 Packet-Switched Bearer Service for Digital Subscriber Signaling System Number 1 (DSS1)
The scope of this standard covers the following procedures at the S@ T@ or U reference point: Circuit-switched access to Packet- Switched Public Data Network (PSPDN) services - case A. This standard defines the use of the procedures of ANSI T1.602 and ANSI T1.607@ when appropriate@ on basic rate interfaces and primary rate interfaces for the establishment and release of circuit-switched calls through ISDN to the access port of PSPDN. These circuit-switched calls may be initiated by the user or the access port of PSPDN. Only the B-channel is used in this instance; Packet-switched access to an ISDN virtual circuit service - case B. This standard defines the use of the procedures of ANSI T1.602 and ANSI T1.607@ when appropriate@ on basic rate interfaces and primary rate interfaces for the establishment and release of packet-mode access connections to a packet-handling (PH) function provided within the ISDN. These packet- mode access connections may be initiated by the user or the Pl! function within the ISDN. B-channels and D-channels may be used in this instance; X.25 LAPB procedures on the B-channel and LAPD procedures on the D-channel@ as described in ANSI T1.602. X.25 LAP procedures are not supported in this standard; X.25 packet level procedures on B-channels and D-channels. NOTE - Alternative methods of access via any bearer channel to Packet-Switched Public Data Networks are for further study. Purpose This interface standard was written to provide a set of requirements for user-network signaling for ISDN support of packetized data transfer@ while conforming@ wherever possible@ with the I-Series Recommendations of the International Telegraph and Telephone Consultative Committee (CCITT)@ and while not compromising the principles of evolution expressed therein. Equipment may be implemented with additional functions and procedures. This standard presents the procedures at the S@ T@ or U reference point for B-channel@ and D-channel access connection on basic rate interfaces and primary rate interfaces to a Packet-Handling (PH) function within the Integrated Services Digital Network (ISDN) to support ISDN virtual circuit service. Procedures at the S@ T@ or U reference point for B-channel access to a Packet-Switched Public Data Network (PSPDN) are also specified. Structure Clause 1 describes the purpose@ scope@ and structure of this document. Clause 2 lists reference documents. Clause 3 lists definitions helpful in interpreting the specifications. Clause 4 provides an overview of packetmode call control and defines the control states for case A circuit-switched calls and case B packet-mode access connections. Clause 5 specifies the message functional definitions. Clause 6 specifies the message structure for case A circuit-switched calls and case B packet-mode access connections. Clause 7 specifies the procedures for packet communication at the S@ T@ or U reference point. Clause 8 specifies the system parameters.