Method and apparatus for bridging local area networks
First Claim
1. A communications system for interconnecting multiple local area networks across backbone networks independently and transparently of protocols above the data link layer and so that the multiple local area networks appear to the users of stations of all local area networks as one large single local area network, said system comprising,a plurality of local area networks with each local area network having at least one station for sending or receiving communications to or from another station using data link frames containing at least a destination address and a source address,at least one backbone network comprising only simplex broadcast channels and connecting two or more local area networks and wherein each backbone network has one and only one transmit simplex channel associated with one or more receive simplex channels,a plurality of bridge means with each bridge means interconnecting across simplex channels a plurality of local area networks to permit one or more stations in one local area network to communicate with one or more stations in one or more of the other local area networks,each said bridge means comprising,network interface means for interfacing the bridge to related local area networks and for sending information in frame format between related local area networks across one or more backbone networks,bridge management means for defining the association, in a backbone network, of the single transmit simplex channel and the receive simplex channels in three possible topologies, i.e. non-rooted, single rooted and multi rooted,learning means for learning the location of end user stations relative to the backbone network so that frames received from the backbone network can be forwarded or discarded,forwarding means for forwarding a frame received from one station in one local area network to a designated station in another local area network across one or more backbone networks independently and transparently of protocols above the data link layer,discarding means associated with each receive simplex channel for selectively discarding frames,wherein the transmit simplex channel characteristics are completely independent of receive simplex channel characteristics and the characteristics of each individual receive simplex channel are independent of other receive simplex channel characteristics, andwherein the backbone network is not required to be related to the local area network access technique or bandwidth.
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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.
204 Citations
19 Claims
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1. A communications system for interconnecting multiple local area networks across backbone networks independently and transparently of protocols above the data link layer and so that the multiple local area networks appear to the users of stations of all local area networks as one large single local area network, said system comprising,
a plurality of local area networks with each local area network having at least one station for sending or receiving communications to or from another station using data link frames containing at least a destination address and a source address, at least one backbone network comprising only simplex broadcast channels and connecting two or more local area networks and wherein each backbone network has one and only one transmit simplex channel associated with one or more receive simplex channels, a plurality of bridge means with each bridge means interconnecting across simplex channels a plurality of local area networks to permit one or more stations in one local area network to communicate with one or more stations in one or more of the other local area networks, each said bridge means comprising, network interface means for interfacing the bridge to related local area networks and for sending information in frame format between related local area networks across one or more backbone networks, bridge management means for defining the association, in a backbone network, of the single transmit simplex channel and the receive simplex channels in three possible topologies, i.e. non-rooted, single rooted and multi rooted, learning means for learning the location of end user stations relative to the backbone network so that frames received from the backbone network can be forwarded or discarded, forwarding means for forwarding a frame received from one station in one local area network to a designated station in another local area network across one or more backbone networks independently and transparently of protocols above the data link layer, discarding means associated with each receive simplex channel for selectively discarding frames, wherein the transmit simplex channel characteristics are completely independent of receive simplex channel characteristics and the characteristics of each individual receive simplex channel are independent of other receive simplex channel characteristics, and wherein the backbone network is not required to be related to the local area network access technique or bandwidth.
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18. A method of interconnecting in a communications system multiple local area networks across backbone networks independently and transparently of protocols above the date link layer and so that the multiple local area networks appear to the users of stations of all local area networks as one large single local area network, each of the local area networks having at least one station for sending or receiving communications to or from another station using data link frames containing at least a destination address and a source address, said method comprising,
interconnecting local area networks through a plurality of bridges with each bridge having at least one associated backbone network which comprises only simplex broadcast channels and which has one and only one transmit simplex channel associated with one or more receive simplex channels, defining in each bridge the transmit simplex channel and receive simplex channels of an associated backbone network in three possible topologies, i.e. non-rooted, single rooted and multi rooted, and learning the location of end user stations relative to each backbone network so that frames received from the backbone network can be forwarded or discarded, forwarding through a bridge a frame received from one station in one local area network to a designated station in another local area network across one or more backbone networks, selectively discarding frames received on the receive simplex channels, employing transmit simplex channel characteristics which are completely independent of receive simplex channel characteristics and employing characteristics of each individual receive simplex channel which are completely independent of other receive simplex channel characteristics, and forwarding frames across a backbone network in a way which is not required to be related to the local area network access technique or bandwidth.
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19. A bridge for a communications system of the kind in which there are a plurality of local area networks with each local area network having at least one station for sending or receiving communications to or from another station using data link frames containing at least a destination address and a source address and of the kind in which multiple local area networks are interconnected across backbone networks independently and transparently of protocols above the data link layer and so that the multiple local area networks appear to the users of stations of all local area networks as one large single local area network, said bridge means comprising,
network interface means for interfacing the bridge to related local area networks and for sending information in frame format between related local area networks across one or more backbone networks and wherein each backbone network comprises only simplex broadcast channels and has one and only one transmit simplex channel associated with one or more receive simplex channels, bridge management means for defining the association, in a backbone network, of the single transmit simplex channel and the receive simplex channels in three possible topologies, i.e. non-rooted, single rooted and multi rooted, learning means for learning the location of end user stations relative to the backbone network so that frames received from the backbone network can be forwarded or discarded, forwarding means for forwarding a frame received from one station in one local area network to a designated station in another local area network across one or more backbone networks independently and transparently of protocols above the date link layer, discarding means associated with each receive simplex channel for selectively discarding frames, wherein the transmit simplex channel characteristics are completely independent of receive simplex channel characteristics and the characteristics of each individual receive simplex channel are independent of other receive simplex channel characteristics, and wherein the backbone network is not required to be related to the local area network access technique or bandwidth.
Specification