Browse Prior Art Database

ISDN Primary Rate Interface with Multiple Protocol Support and Scalable Performance

IP.com Disclosure Number: IPCOM000108105D
Original Publication Date: 1992-Apr-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 4 page(s) / 141K

Publishing Venue

IBM

Related People

Saalmueller, J: AUTHOR

Abstract

This article describes a very powerful solution for an ISDN (integrated services digital network) primary rate interface. This interface is capable of handling all standard protocols recommended by CCITT (Consultative Committee on International Telegraph and Telephone). The intention of the proposed concept is to allow the direct attachment of a primary rate interface to an ES/390 system. The described interface supports not only HDLC (high-level data link control)-based protocols but also bit stuffing (V.110) or multiplexing (V.120) protocols whose support is important for connecting equipment of other vendors. In addition, voice handling is possible.

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ISDN Primary Rate Interface with Multiple Protocol Support and Scalable Performance

       This article describes a very powerful solution for an
ISDN (integrated services digital network) primary rate interface.
This interface is capable of handling all standard protocols
recommended by CCITT (Consultative Committee on International
Telegraph and Telephone).  The intention of the proposed concept is
to allow the direct attachment of a primary rate interface to an
ES/390 system. The described interface supports not only HDLC
(high-level data link control)-based protocols but also bit stuffing
(V.110) or multiplexing (V.120) protocols whose support is important
for connecting equipment of other vendors.  In addition, voice
handling is possible.

      ISDN is the future technology in telecommunications. Compared
with analog methods currently used, it considerably enhances the
security, the quality and the speed of data transmission.  While the
basic rate interface with two data (B) channels is for applications
in the end-user environment (phone, FAX, PCs, terminal adapters), the
primary rate interface with 30 data channels is for PBX (private
branch exchange) applications and direct connection of multi-user
workstations and mainframes to the ISDN network.  The I., X. and V.
series of the CCITT recommendations allow the use of several
different protocols (such as V.110, V.120, LAP-E (HDLC)) in
B-channels, voice or analog modem signals.  All of these require
specific processing of the data received or to be transmitted.

      A straightforward way to build a primary rate interface is to
use a chipset to access the B-channels via a memory and to process
the data of the 30 B-channels by one processor and a DMA (direct
memory access) interface.  The data is then directly routed to the
host or, in the case of a gateway, directly to another I/O unit.
However, postprocessing of the data (e.g., analog modem functions
requiring filter functions and modem signal decodes or asynchronous
protocols, such as V.110, additionally requiring start/stop handling)
necessitates a lot of performance which leads to complicated bus
structures at the memory interface of the I/O processor or to load
transfer to the host CPU.

      The described approach affords a scalable performance for the
several requirements and multiple protocol support.

      To access the primary rate interface, a vendor chipset is used.
The line front end is built from an IPAT (ISDN primary access
transceiver) and an ACFA (advanced CMOS frame aligner) which provides
for a time slot-oriented bus (PCM (pulse code modulated) highway) on
the local side...