Abstract: A distributed queue dual bus (DQDB) network has two, oppositely-directed, unidirectional busses. A node with data to send on one bus, can request access to that bus, by sending a bus request signal to all nodes upstream on the bus. The bus request signal is sent to the nodes as part of the traffic flowing on the second bus. Each node counts the number of successive bus request signals transported on the second bus. In a multiple priority system, multiple counts are maintained, one for each priority level. When a given or local node detects an idle slot on the first node, it may write data into that slot if there are no pending downstream access requests of higher priority and if the local node has allowed enough idle slots to pass since its last write operation to service access requests existing at the time of that operation at the same or higher priority levels.

Abstract: In complex networks, data frames may be routed through different systems having different frame or addressing requirements. When the frames are transferred or bridged between such systems, known changes may have to be made in the frame contents to accommodate these requirements. To maintain the integrity of error checking provided by Cyclical Redundancy Checking (CRC) techniques, a system receiving a frame uses an improved Frame Check Sequence value modification technique which modifies a Frame Check Sequence (FCS) field value only as a function of the known or planned changes to be made in the frame. If unplanned changes (that is, errors) are introduced at the receiving system, application of standard CRC error checking techniques at the next system to receive the frame will indicate those errors.

Abstract: Enhanced type 2.1 nodes for SNA networks provide network routing of information between non-adjacent network nodes and program-to-program linkage across the network. These nodes are called "advanced peer to peer networking" (abbreviated APPN) nodes. Network state information, describing the topology and resources of the network is disseminated betweeen APPN nodes by a first data link control exchange of identification (XID) information indicating node type (and thereby distinguishing APPN nodes from other nodes) and other exchanges conducted over a newly defined control point to control point (abbreviated CP--CP) session having a message architecture unique to APPN type nodes. The XID exchange is conducted whenever a link between nodes is activated, and when the exchanging nodes are both APPN, and if both are available to participate in as CP--CP session, they automatically engage in a second exchange of session binding signals which establish a pair of sessions between the nodes.

Abstract: In a communications network, each network node can maintain its own list of network resources in a topology database. When the state of a resource "owned" by a particular node changes, that node broadcasts a topology database update (TDU) message to adjacent nodes. Each adjacent node updates its own topology database and rebroadcasts the message. To minimize the amount of information that must be included in TDU messages when two nodes are reconnected after an outage, each node assigns flow reduction sequence numbers (FRSNs) to TDU meassages and keeps a record of the FRSN for the last TDU message sent to an adjacent node. The node also records, for each resource in its database, the FRSN of the last TDU message including that resource. When two nodes are reconnected, the sending node includes in the TDU message only those resources having a FRSN greater than the FRSN assigned to the last TDU sent to the adjacent node to which the TDU message is directed.

Abstract: The invention is an improvement in a liquid crystal display device of the type having spaced front and rear glass panels, a transparent electrode layer, and an array of individually addressable pel electrodes separated from the transparent electrode layer by a cavity filled with liquid crystal material. The improvement comprises a color filter layer in the form of a decal pattern. The decal pattern is formed using interference film techniques which form an inorganic color filter. The decal is placed on one of the glass panels using known decal transfer methods. The inorganic nature of the color filter layer and the decal transfer methods allow for enhanced optical density of the color liquid crystal display.

Abstract: Decal technology is employed to provide a color filter layer for a thin film transistor liquid crystal display device. The red/green/blue color regions and an opaque surround are printed on a suitable substrate using gravure printing techniques and colored glass frit materials. Once the printed decal is transferred to one of the glass panels, it can be heated to fuse it to the glass. Electrodes can be deposited directly on this fused color filter layer.

Abstract: The links in a data communications network following Systems Network Architecture may be categorized as limited resource links if those links are shared access transport facilities, such as a switched telephone network, X.21, X.25 or token ring local area network facilities. In setting up LU--LU sessions between network users, a limited resource session identifier field is set to a specific value if any of the links in the session data path is defined as a limited resource link. When a conversation between two users ends, the primary logical unit responds by determining whether the session has been identified as a limited resource session. If it has, the primary logical unit initiates action to deactivate the session without waiting for network control operation action. Allowing the primary logical unit to deactivate a limited resources session assures that the limited resource link or links will not remain allocated needlessly to an unused session.

Abstract: A least weight route computation algorithm for use in computing routes through a data communications network is improved by recording the number of equally weighted paths to a particular node through different predecessor nodes. If a route must be selected to the particular node, the relative numbers of equally weighted routes through different predecessor nodes determines the probability with which a route will be selected through the particular predecessor node.

Abstract: The invention enables two nodes in a communications network to dynamically establish the transmission group number used to partially identify a given link between the nodes. When the link is being activated, both nodes simultaneously propose either a zero or a non-zero number to each other in an exchange of exchange identification (XID) messages. If only one of the nodes proposed a non-zero number, that non-zero number is selected as the transmission group number. If both nodes had proposed zero or both had proposed non-zero numbers, predetermined criteria are employed to select a controlling node. The controlling node chooses the final transmission group number and communicates that choice to the non-controlling node.

Abstract: A LOCATE search dynamically locates resources (e.g., logical units (LUs) and transaction program and files associated with LUs) in a computer network so that a session can be established between the origin and the destination of the search.In a network which includes end nodes associated with server nodes, a resource contained in any node is located by a requesting node. The requesting node initiates a search of the resources residing within itself. If the resource does not reside in the requesting node, the server node searches the resources known to the server node that reside anywhere in the nework. If the resource is not known by the server node, it searchers all resources that reside in its associated end nodes. If the resource does not reside in the associated end nodes, either a request is sent to a central directory if one exists or a search of all resources in the network is made.

Abstract: When computing a least weight path from an origin node to a destination node in a data communication network, a route-computing network node uses information provided by the origin and destination nodes to compute least weight routes from those nodes to adjacent network nodes. The route-computing network node uses information in the topology database to compute least weight routes from network nodes adjacent the origin node to network nodes adjacent the destination node. The results of the computations are concatenated to determine an optimum route from the origin node to the destination node. The topology database need not include information about the transmission groups connecting the origin/destination nodes to network nodes.

Abstract: Each network node in a communications network maintains its own copy of the network topology database defining network resources. Each resource record contains a "timer" field which is initially set to a maximum value but which may be decremented on a daily basis. If the timer field is decremented to zero without being reset, the node unilaterally removes the resource record from its copy of the database. The timer field will normally reach zero only for obsolete resource records since each network node responsible for a resource broadcasts a timer-resetting message for the resource (1) each time the resource status changes, (2) when the node first joins or rejoins the network, and (3) on a periodic (weekly) basis regardless of whether conditions (1) or (2) have occurred.

Abstract: An improved holographic scanner includes circuitry for adjusting the frequency with which an analog photodetector signal is sampled in accordance with the focal length of the scanning beam produced by the active holographic facet. Two embodiments are shown. In one embodiment, facet-edge signals are used to track the facets. A processor retrieves a predetermined frequency scaling factor appropriate for each facet. In the other embodiment, a holographic disk carries an auxiliary data track. The track has timing indicia with spatial frequencies dependent upon the focal length of the adjacent facet. The timing indicia are used to control the output of a voltage controlled oscillator in a circuit including a phase locked loop.

Abstract: A wavelength agile optical receiver can be used in an optical equivalent of an "order wire" data communication system. The receiver includes an acousto-optic grating which can be tuned to deflect optical signals received at a particular wavelength by changing a drive signal produced by an acoustic transducer. A multi-wavelength optical signal is applied to the grating. Under "order wire" or quiescent conditions, light at an order wire wavelength is deflected onto a split optical detector. A processor is employed to select control signals for a voltage-controlled oscillator which drives the acoustic transducer. The processor can cause the transducer output to be changed to provide deflection of optical energy at a selectable wavelength onto the detector.

Abstract: A multi-faceted holographic disk can be copied in a one-step process by using a source disk, actually a sandwich of two thin film layers of photosensitive material. The first thin film layer is capable of producing multiple reference beams simultaneously. The second thin film layers is a "master" copy of the disk to be copied. Both layers are produced using known off-axis holographic techniques. A target disk, having an unexposed film of photosensitive material is located ajacent the second thin film layer. The source disk is illuminated with coherent light, preferably in the form of a conical beam with an apparent point of origin on an axis through the common centers of the source and target disks. Several optical elements capable of producing the conical beam are illustrated.