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DATA FRAME ROUTING METHOD AND NETWORK BRIDGE
US2012044837
A method operates at the data link level. Each bridge associates, during a guard time, the port through which a frame is first received with a source MAC address until a unicast reply frame confirms the matching two-way path between the source and destination addresses. Any frame from the same source received through another different port is discarded. Each bridge forwards the received broadcast frames through the rest of the ports, except those involving prohibited (down-up) turns, and deviates (or optionally returns) the unicast frames with an unknown or aged destination address through the spanning tree. The protocol can operate with encapsulation in the border bridges or without encapsulation, using in this case the replacement of universal MAC addresses in the border bridges with local MAC addresses. The establishment and control of paths can optionally be performed proactively by the border bridges, especially the bridges connected to servers.
The advantages are that it requires a smaller number of MAC addresses to be learnt and only requires learning the prefix of the bridge instead of that of the hosts. Mechanisms for controlling the consistency of the ARP caches in the hosts are necessary. Briefly, other advantages of the invention over the prior state of the art are: In comparison with the protocols routing frames, it allows aggregating routes between the border bridges by means of hierarchical addressing. In comparison with the protocols operating in the control plane such as LSOM (“Link State Over MAC”) and others such as HURP which assign hierarchical local addresses (HLMACs), it does not require the periodic exchange of routes between bridges, operating in a transparent manner by means of backward learning on the data frames. In comparison with the protocols which are not compatible with the Ethernet frame format, the protocol is compatible.