Abstract: A source-aware bridging scheme for supporting bridging between a noisy (“unreliable”) network and another, reliable network. Each device connected to the medium of the unreliable network includes a source-aware MAC that maintains a Bridge Proxy Destination Address list (BPDAlist) of all destination addresses that reside on the other network and are reached by a bridge. The BPDAlist information can be learned by the source-aware MAC during a frame receive and/or received during a channel estimation cycle. The list associates destination addresses with the address of the particular bridge through which the destination addresses are accessed. The bridge serves as a proxy with respect to those destination addresses and thus maintains its own list of the destination addresses for which it serves as proxy, or, IAPlist. The IAPlist can be learned, or passed down to the source-aware MAC from a learning bridge process or from the local host to which the device is coupled.

Abstract: A partial ARQ protocol for multicast and broadcast transmissions in network devices operating in a shared medium access network. To support the partial ARQ, a media access control (MAC) protocol uses robustly transmitted frame delimiters and a MAC management frame structure. In a multicast or broadcast frame with partial ARQ, a destination address field is set to that of a selected proxy device's address, and the address of the intended recipients (of group address of the intended recipients) is placed in an entry in the MAC management frame structure. The frame also contains a multicast flag set to indicate that the transmission is intended for more than one device and a value in the frame delimiters to indicate that a response is requested. Upon receipt of such a frame, the proxy device specified by the destination address field provides an appropriate response type on behalf of the group.

Abstract: A printing apparatus having a moving carriage with a snap action switch mounted thereon to initialize the left and right margins of the printing apparatus. The carriage is moved to the left until the snap action switch strikes a stop on the frame of the machine. The carriage is then moved a predetermined distance to the right, and a left margin counter is set to zero while a right margin counter is set to a count representative of the width of printing between margins. The counters are incremented and decremented by movement of the carriage with the zero point of each counter representing presence of the carriage at that associated margin. Manual devices are provided for setting a narrower printing field with wider margins at either side by resetting the margin counters. Also, a margin release allows movement of the carriage outside of the narrowed printing field but never outside of a maximum printing field.