Abstract: Methods and apparatus for exchanging frames between bridges distribute load sharing in a communications network. The communications network is of the kind in which bridges, and related stations and local LANS, e.g. Ethernet LANs and 802 LANs, can be linked by paths in a plurality of sub-networks and wherein the bridges are linked to support a Spanning Tree Protocol (STP) which elects one bridge as a root and then with respect to said root, computes and utilizes one and only one loop-free set of primary paths between all bridges. Remaining paths, i.e. paths other than said STP primary paths, between the bridges are examined as possible sub-network paths for a Distributed Load Sharing (DLS) configuration in which frames exchanged between certain stations can utilize more than the STP one set of primary paths. Certain ones of the remaining paths are selected as DLS paths under certain conditions and frame are routed over a selected DLS path only when those frames meet certain criteria.
Abstract: A controller for a bridge interconnecting local area networks operates in two modes. In a first mode the controller receives and transmits station data frames with previously appended frame check sums. In a second mode the controller responds to requests for information from stations by generating data frames from an associated memory. The controller computes and appends frame check sums and then transmits the frames and check sums to the requesting station. The controller is constructed and is effective to operate in a way which insures that all station data frames transmitted from stations to the bridge are received by the bridge without interruption or loss during all periods of operation. The controller receives all such frames at all times, including the time intervals during which circuitry in the controller must be off line and reprogrammed for changing operation between the first and second modes.
Abstract: A communications system interconnects local Area Networks (LAN's) across broadcast simplex channels. The LAN's are connected independently and transparently of protocols above the data link layer so that the system appears to the user at a station in one Local Area Network as one large single network. A bridge interconnects the LAN's across simplex channels. The bridge is constructed to permit more than two local area networks to be interconnected across simplex channels to the bridge and to provide communication between stations.
Abstract: A waveguide apparatus guides a first pair of horizontally polarized transmit and receive frequency signals independently of and in parallel with a second pair of vertically polarized transmit and receive frequency signals. The waveguide apparatus is constructed to operate across the 3.7 to 6.425 GigaHertz band with a very narrow bandwidth for the transmit frequency and a very narrow bandwidth for the receive frequency and with a single size of rectangular waveguide for separating the transmit and receive frequencies. This construction simplifies frequency separation filtering techniques and provides effective operation over this broad band with an apparatus which is efficient in terms of space, compact and implemented by a simple package.
Abstract: A method and apparatus for increasing the capacity of present and future satellite communication systems transmits signals from correspondent pairs of earth stations simultaneously in channels that have at least a partial overlap in bandwidth. Each receiver at each earth station subtracts from the received composite signal the portion of the composite signal which was transmitted by the receiving earth station. This leaves a desired signal which corresponds to the signal transmitted by the other earth station of the correspondent pair and which is then demodulated. Each receiver at each earth station thus reconstructs an estimated target signal which has the amplitude, delay, frequency and phase of the signal as transmitted from the earth station and retransmitted by the satellite. The reconstructed target signal provides a very precise estimate of the portion of the composite signal transmitted by the earth station.