International Business Machines Corporation

Pitro A Zafiropulo

Werner K Bux

Erwin A Zurfluh

Johann R Mueller

Mehdi M Nassehi

Felix H Closs

Johann R Muller

Harmen R Van As

Hans R Mueller

Daniel Wild

Karl Albert Kuemmerle

Erich Port

Ivor Jones

A protocol and format for multiple accessing and transporting information in a Distributed Queue Dual Bus communications network includes count field in which stations can reserve multiple time slots for transporting data.

Method and apparatus for distributed queue multiple access in a

A distributed queue multiple access technique is disclosed for a system comprising two counterflowing transmission busses (A,B), plural stations (i, j) connected between them, and a headend station generating slots on the first one (A) of the busses; each station transmitting access requests on the second one (B) of the busses and determining its right to transmit data in slots on the first bus on the basis of access requests it has seen. Each station maintains a FIFO queue (41) for sequential storage of numbers representing external (EXT-REQ) and local (LOC-REQ) access requests. To achieve correct timing between access requests entering the queue from the second bus and respective free slots passing a station on the first bus, a station-individual delay is introduced by maintaining in a FIFO delay storage (71) a specific number of entries. This results in an equally fair treatment for all stations, and guarantees the availability of consecutive free slots for any station which requested them.

In a switching exchange for circuit-switched/synchronous traffic (CS) and packet-switched/asynchronous data packet traffic (PS), transmission lines communicate with FIFO buffers interconnected by a data bus on which information is transferred in periodic frames. CS traffic is collected in FIFO input buffers in minipackets each carrying a local routing address. The last minipacket per frame period is identified by a special end tag. Once per frame a daisy-chain signal propagates through access control lines to sequentially read out from FIFO input buffers all CS minipackets up to the next one having a special end tag, transferring them through the data bus to FIFO output buffers. Thereafter a token access mechanism starts enabling selective PS data packet transfer between FIFO input and output buffers. When a new frame begins, and PS data packet transfer is interrupted for a CS minipacket readout process, and thereafter transfer of the interrupted PS packet is resumed.

Method and apparatus for switching information between channels for

In a local area communication system comprising token rings (11) with synchronous bandwidth managers SBM (15) for issuing priority tokens for quasi-synchronous frames at regular intervals, the rings are interconnected by a time division muliplex PBX unit (21) via their SMB units. Buffers are provided in each SBM for synchronous information blocks transferred from and to the ring, and the TDM control (31) can independently access these buffers for TDM switching of the individual bytes of said information blocks. Besides this PBX interconnection for synchronous information or voice, the rings are also interconnected by a backbone bus or ring for transfer of asynchronous data between rings. A special slot rearrangement procedure is provided to improve the filling of time slots in the quasi-synchronous frames that are no longer used after release of a connection, to allow for adapting the frame length (number of issued slots) to the number of existing connections.

Local area communication system for integrated services based on a

A method and a TDM multiplexer by which circuit-switched synchronous data and packet-switched asynchronous data are optimally combined for transmission over a common channel. Time slots of variable width are assigned to circuit-switched traffic, while the remaining capacity of the TDM frame is used for transmission of store-and-forward traffic which is inserted in the gaps between assigned time slots in the form of an intermittent bit stream.

Method of transmitting information and multiplexing device for executing

A closed loop communication system in which the terminals are grouped into priority classes. Any terminal can seize a free channel if certain priority conditions exist. A channel (frame) is always preceded by a header comprising a priority request field and a priority grant field. The request field has n bits assigned to the n priority classes; a terminal requiring service sets that bit to '1' which corresponds to its class. Thus, the controller receives a compiled overall request and inserts, for the next cycle, into the grant field an indication as to which priority class or classes are now allowed access to the channel. This is accomplished by shifting the contents of the request field to the grant field. A terminal can only seize the channel if its priority class is allowed for that cycle by the grant field, and if the channel is still free.

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Ruschlikon, Switzerland

Pitro A Zafiropulo