Abstract: A communication network consists of end units (EUs) and distribution units (DUs) coupled together by links which may include local area networks (LANs). The units maintain neighbor tables by sending out Hello messages which indicate the unit type and contain the network service access point (NSAP) IDs or addresses of the units. Data messages (packets) mainly originate and end at EUs. An EU maintains only partial routing information about neighbors, while the DUs collectively maintain complete information about all NSAPs. So if an EU wants to send a packet to an EU which is not a neighbour (and sometimes even if it is), it need merely send it to a neighboring DU; that DU, along with the other DUs, must find a route to the destination EU. This invention provides a hybrid unit (HU), which acts as a DU to EUs but as an EU to DUs. The HU provides DU-like message forwarding but only on a local basis within a subnetwork of EUs and HUs.

Abstract: An encryption system employing a one-time key-pad uses a shared secret number and a one-way hash function with which both the originator and recipient of a message generate successive segments of a key-pad to encrypt and decrypt the message respectively. In one arrangement each key-pad segment is generated by applying the hash function to a combination of the secret number and the previous key-pad segment. In the other embodiment of the invention, each key-pad section is generated by applying the one-way hash function to a combination of the secret number and a corresponding segment of the ciphertext version of the message.

Abstract: Frame processing apparatus, and a related method for its operation, for use in a station connected to a token ring network, to ensure rapid stripping of frames from the network without reference to source addresses in the frames, and in spite of the possible presence of extraneous no-owner frames on the network. The adverse effects of extraneous no-owner frames are avoided by any of three techniques. First, transmitted information frames are preceded by a start strip delimiter frame and followed by an end strip delimiter frame. The process strips all incoming frames (except tokens and ring initialization frames, which are specially handled), but does not count the stripped frames until the start strip delimiter frame is detected. Therefore, extraneous frames preceding the transmitted information frames will be stripped but not counted, and all of the transmitted frames will be stripped. In another approach, an estimated stripping time is used to terminate stripping.

Abstract: A system for stripping frames transmitted by a station on a token ring network is disclosed. During operation of the system, the station receives a grant of permission to transmit onto the network. In an example embodiment, the grant of permission is a token. After receipt of the grant of permission to transmit, the station transmits one or more information frames onto the network. Upon transmission of the information frames, the station stops forwarding frames received from the network, thus removing received frames from the network. Removing received frames from the network is referred to as `stripping`. Following transmission of the information frames, the station transmits an end strip delimiter frame onto the network. Upon receipt of the end strip delimiter frame, the station terminates stripping. In an example embodiment, the system is used in a bridge station, the bridge station connecting a first network with a second network.

Abstract: A system to enable individual locator devices or badges developed for location of people or objects to (1) determine whether their identification transmissions are received by sensor stations and to (2) take appropriate actions when the transmissions are not received. Each badge in the system can transmit to any sensor station in the system a request for an acknowledgement within a set interval of time. Each time a sensor station receives a request for acknowledgement from a badge the sensor station sends a message of acknowledgement to the badge. If the badge does not receive an acknowledgement within the set interval of time, the badge takes appropriate action due to its occlusion from the system. If the badge receives an acknowledgement within the interval of time, it resets its internal timer.

Abstract: A controller for a communication system having a plurality of networks and a plurality of stations communicating with each other by sending messages from a source station to a destination station is disclosed. A plurality of stations may be assigned to a group. A communication history for the stations is determined, where the history corresponds to the messages communicated. The stations are connected into a common network in accordance with the communication history. The communication history corrresponds to a series of packets and is based on a source address and a destination address of each of the packets. A station may have a matrix, the matrix having rows indexed by source system address and columns indexed by destination system address, for storing a value indicating a quantity of information transferred from each station to each other station.

Abstract: Two devices HR and FR are coupled to a bus with a common memory via a port controller. Device HR requires a high (or maximum) average rate of access, device FR requires a fast response (minimum latency) in establishing access. Request signals HRQ, FRQ from the devices are latched by latches 20 and 21, passed as HRX, FRX through an arbitration or resolver circuit 22 as HRY, FRY to a sequence control unit 23 to initiate an access cycle. Cycle timing is determined by a delay line timebase circuit 24, which responds to a single change of level of a signal DLY (in either direction). Latch 21, when set, generates an request pending signal FRRP which is fed to the HR device to cause it to increase its cycle length so that the FR access cycle will finish before the next HR access cycle is initiated.

Abstract: An apparatus for storing and retrieving data acts as an interface between modules such as data collection devices and data analysis tools. The apparatus provides the capability of maintaining a data standard so the number of translation tools needed to transfer data from one module to another is reduced. The apparatus maintains the data standard by means for storing a configuration data structure having table data structures. The configuration data structure and the table data structure define a data model. The data model is editable. Complex, as well as simple, items may be stored in the table data structure.

Abstract: A network adapter with an interrupt generation circuit to minimize the number of host computer system interrupts needed to notify the host computer system that the network adapter has consumed one or more host memory buffers. The interrupt generation circuit issues an interrupt to the host computer system when the host computer system has entered both a transmit sleep state and a receive sleep state, and the network adapter has consumed a host memory buffer not processed by the host computer system. When the host computer system has no work to do with respect to transmit buffers in the host computer memory, it enters a transmit sleep state and indicates to the network adapter the last transmit buffer it processed. When the host computer system has no work to do with respect to receive buffers in the host computer memory, it enters a receive sleep state and indicates to the network adapter the last receive buffer it processed.

Abstract: A database-management system (10) generates bounded-disorder indexes on its database keys. In such an index, the leaf nodes (51, 62) are large and are divided into a number of buckets (52, 54, 56, 58), only one of which ordinarily is accessed in any given single-record database operation. The key values in a leaf node are distributed among the leaf node's buckets in accordance with a hashing function. The lockable ranges locked for scanning functions are defined in accordance with key-valued locking, in which each lockable range is bounded by successive key values that exist in the database. But the multiple-bucket accesses that would otherwise be required, because of the hash-function distribution of key values among a node's several buckets, are avoided because the lockable ranges are defined by the sequence of key values in the bucket rather than in the node.

Abstract: A technique for managing bidirectional data flow between a first data bus, such as in a local area network, having a fixed data flow rate once access has been obtained, and a memory or storage device connected to a second data bus having variable latency. Inbound data from the first data bus are temporarily stored in a receive buffer memory and later forwarded to the storage device. Outbound data bursts are retrieved from the same storage device, temporarily stored in a transmit buffer memory, and later transmitted onto the first data bus. The invention controls the steps of forwarding inbound data to the storage device and retrieving outbound data from the storage device, in such a manner as to make efficient use of the second data bus and to minimize the possibility of overflowing the receive buffer memory during a receive operation, or underflowing the transmit buffer memory during a transmit operation.

Abstract: An apparatus for storing and retrieving data acts as an interface between modules such as data collection devices and data analysis tools. The apparatus comprises a means for storing a configuration data structure, the configuration data structure having a plurality of data items. The attributes of a data item are a name, a data type, a size, and a mapping parameter. The plurality of data items may contain administrative data, instrument identification data, global sample identification data, detection method data, raw unprocessed data, data peak processing method, data peak processing results, instrument calibration data, multicomponent sample calibration method, results from multicomponent sample calibration, sample sequence data, dimension data, control events for instrument data, reprocessing method data, and reprocessing results data. The apparatus provides the capability of maintaining a data standard so the number of translation tools needed to transfer data from one module to another is reduced.

Abstract: A method for connecting a first communications system with a second communications system is disclosed. A first frame is received at a first station. The first station is connected to both the first communication system and the second communication system. The first frame has a destination address field, and the destination address field contains a desired destination address. The first station forwards, in response to the desired destination address, the first frame onto the second communications system as a second frame, and the first station writes a second destination address into a destination address field of the second frame. The first station writes the desired destination address into a predetermined field of the second frame. The first station writes, an indicator into the second frame, the indicator is capable of being interpreted by a receiving station to mean that the desired destination address is written into the predetermined field of the second frame.

Abstract: A novel mechanism prevents interleaving of packet cells from different source nodes on the same multicast port group at switches of a multicast virtual circuit in a cell-switched network: however, different cells bound for different multicast port groups may be interleaved. The mechanism comprises specific routing information that is stored in each multicast group port entry of a forwarding table located within each switch of the multicast virtual circuit. The forwarding table also stores information relating to each multicast port group including a virtual circuit value for each port of the multicast group. The specific routing information is provided for each multicast port group entry to notify the switch when data traffic for a particular packet is pending through a port of the multicast group and when that data traffic ceases, i.e., when the "end-of-packet" is reached. This ensures that the packets may be correctly reassembled at the destination nodes.

Abstract: A flow control system is disclosed, for a transmitting node and a receiving node. The transmitting node and the receiving node are linked together through multiple connections or virtual circuits. The receiving node includes a connection specific pool of buffers for receiving data transmission units from the transmitting node over each specific connection, and a common pool of buffers for storing data transmission units received from the transmitting node over any of the connections between the transmitting node and the receiving node. A flow control circuit in the transmitting node limits the number of data transmission units transmitted from the transmitting station, and not yet copied out of the receive buffers in the receiving node, to the total number of receive buffers in the receiving node.

Abstract: A connection apparatus for connecting a first communication system with a second communication system and a third communication system. A first frame is received from the first communication system, where the first frame has a multicast address as a destination address, and where the destination address requires the first frame to be transmitted onto the second communication system. The multicast address is translated into a functional address, and the functional address is written into a second frame transmitted onto the second communication system. The second frame is received and is transmitted onto a third communication system, and the functional address is translated into a multicast address for the third communication system, and the multicast address is written into a destination field of the frame as it is transmitted onto the third communication system. The second communication system may be a token ring system based upon an IEEE 802.

Abstract: A communications system is disclosed, having a first communications link, a second communications link, a first end station attached to said first communications link, a first packet forwarding apparatus attached to the first communications link, a second end station attached to the second communications link, and a second packet forwarding apparatus attached to the second communications link. Each packet forwarding apparatus routes packets it receives having destination address equal to a data link destination address of the apparatus, and bridges all other received packets. When the first end station wishes to send a packet to the second end station, it first transmits an ARP request message to learn the data link address of the second end station. The first apparatus receives the ARP (Address Resolution Protocol) request message, and determines that the end station for which a data link address is requested is attached to a remote communications link.

Abstract: A way of doing source address and destination address lookups is described, as may be used in a packet data communication system. A way of searching a relatively large database is described, using a combination of programmable hash algorithms, binary search algorithms, and a small content-addressable memory (CAM). The technique is efficient in space, time and cost, compared to prior methods. For example, prior methods using conventional binary reads may have used thirteen reads, whereas this technique requires on average two reads, with a worst case of four reads.

Abstract: A technique for establishing and maintaining full duplex communication between two stations connected to a token ring network, without physically reconfiguring the station connections or otherwise disturbing the network. Each station continually performs a two node test to ascertain whether there are only two active stations on the network, and updates a two node flag that indicates whether or only two active stations are present. The two node test uses both upstream neighbor and downstream neighbor addresses to update the two node flag, and requires validation of either one of these addresses if the other one of them appears to have changed since the previous observation. A concurrently running full duplex control process uses the two node flag and other conditions to decide whether to initiate or continue transition to full duplex mode.

Abstract: An apparatus for correcting an X-ray tomographic image is presented, where the tomographic image is created by measuring an X-ray transmission coefficient at each of a plurality of X-ray beam paths through an object to enable reconstructing a tomographic image of the object. There is a device for selecting a plurality of volume averaged voxels along at least one of the X-ray beam ray paths, and for placing contiguous volume averaged voxels in a run length of volume averaged voxels, to make a plurality of run lengths of volume averaged voxels. There is a device for dividing the plurality of run lengths of volume averaged voxels into a plurality of subslices. There is a device, responsive to the plurality of subslices and responsive to the plurality of run lengths of volume averaged voxels, for computing a corrected value of X-ray attenuation coefficient for the X-ray beam ray path.