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: An air and water vapor permeable open cell solid resin foam resistant to passage therethrough of noxious chemicals in liquid or vapor form said foam having dispersed therein a particulate adsorbent material for said noxious chemicals said particulate adsorbent material being bonded in said foam by an organic binder which is substantially free from substances which substantially deactivate the adsorbent.

Abstract: Laminated fabric materials which are resistant to the passage of noxious chemicals in the form of liquids and condensible vapors and gases, but which are relatively permeable to air and water vapor, are described. Said laminated materials comprise (a) an air and water vaporpermeable open cell solid resin foam resistant to passage therethrough of noxious chemicals in liquid or vapor form, said foam having dispersed therein a particulate adsorbent material for said noxious chemicals, said particulate adsorbent material being bonded in said foam by an organic binder which is substantially free from substances which substantially deactivate the adsorbent; and (b) an air and water vapor-permeable fabric backing to which the aforesaid foam is bonded.