International Business Machines Corporation

Felix H Closs

Johann R Mueller

Pitro A Zafiropulo

Werner K Bux

Harmen R Van As

Robert P Lee

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 demand access broadcast transmission method and means is capable of supporting random port access and any-to-any transmission at very high data rates. A communication medium (FIG. 2) formed from an inverted tree network of nodes (1, 18, 22) and full duplex connecting links (13, 17, 19) permits the establishment of a path lock up-link through the network from a demanding port to a root node on a first-come first-serve demand access basis with arbitration at each distinct tree node level (FIG. 3). Broadcast transmission is perfected down-link over all fan-out paths from the root node. Collision is avoided by locking a path to a port and by limiting race conditions among active ports to only the leading edges of messages. Thus, relinquishment of a broadcast channel overlapped with transmission of a message does not result in path seizure since the occurrence of message leading edges is the singular path connection invoking event.

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Adliswil, Switzerland

Felix H Closs