International Business Machines Corporation

International Business Corporation

David R Hughes

Hollis P Posey

Alexander Polischuk-Sawtschenko

Robert Thomas Cato

James M White

Brian Edward Blair

Arthur Latimer Bond

Arthur M Wiencken, Jr

Carl J Moreschi

A data source on a main local area network (LAN) transmits broadcast messages via bridges to remote stations. A ring buffer in a bridge on the main LAN buffers a selected number of packets received from the data source. When the main bridge on the main LAN receives a 'Lost Frame Message' from a remote bridge, not on the main LAN, the main bridge backs up to the address of the lost packet in the ring buffer, and retransmits the lost packet and then continues sequential transmission of subsequent packets. If buffer is, filled above a pre-set criteria, retransmission is slowed or stopped until buffer is mostly emptied.

Data distribution network with improved broadcast feature

A procedure for bringing-up and/or establishing the operability of a distributive data processing system comprises the steps of providing, at each terminal of said system, a display having a plurality of individually activatable indicators and/or indicia configured in a predetermined geometrical pattern with the position in the pattern and the electrical state of each indicator being representative of the operational readiness of an assigned terminal; running a series of operational tests in each terminal and selectively enabling the indicator and/or displaying an alphanumeric character representing said terminal on the successful completion of the operability tests.

Method of monitoring the bring up of all units in a multiple system from

Apparatus and method for defining I/O devices connected to terminals of a distributive data processing system and for downloading programs from a control computer into said terminals. A global listing containing identities of all devices that can be coupled to the terminal is prepared at each terminal. A configuration list of devices which are actually coupled to the terminal is derived from the global list. The configuration list is stored at the terminal and at the control computer. Thereafter, only programs that are required for controlling the devices that are actually coupled to the terminal are downloaded into the terminal.

Self configuring terminal which polls loop network and generates list of

Described is an architecture and protocol for exchanging messsages within a distributive data processing system. Instead of transmitting a frame with a beginning flag field (SDEL) followed by an address field as is the usual case, the SDEL field and address field collapsed and merged into a single field. The field includes a control bit whose setting determines whether the field is the beginning of a frame or otherwise. A second control bit within the single field is used to identify the type of message being transmitted and the response that a recipient station is permitted to return to a control unit issuing the message. The protocol is well suited for framing messages in the well known SDLC communications format. In this format it allows the detection of delimiters without resorting to bit stuffing.

Method and apparatus for communicating with remote units of a

A digital data communication network in which half-duplex communications are established between a central station and a plurality of remote terminal devices under control of the central station and in which said remote terminal devices are grouped and each group is serially connected and receives data signals in parallel over a simplex link from the central station and in which one group of serially connected stations is selectively connected to a second simplex link for transmitting, in a predetermined sequence, data signals to the central station.

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Raleigh, NC, United States of America

David R Hughes