Abstract: A distributed memory switching hub interconnecting heterogeneous local area networks operating at different transmission speeds for receiving, storing and forwarding frames of data. The distributed memory switching hub employs a distributed memory architecture in which memory storage for frames of data received and to be transmitted is located at each low speed LAN port of the distributed memory switching hub. A distributed memory architecture renders unnecessary the need for a central programmable processor or shared common memory to store and forward frames received by the distributed memory switching hub.

Abstract: A plurality of video dynamic random access memory devices (VRAMs) distributed among low speed local area network ports of a distributed memory switching hub interconnecting heterogeneous local area networks operating at different transmission speeds for receiving, storing and forwarding frames of data. The distributed memory switching hub employs a distributed memory architecture in which VRAM devices located at each low speed LAN port of the distributed memory switching hub store frames of data received or to be forwarded. The VRAM device is comprised of serial access memory (SAM) coupled to and transmitting frames of data with a high speed internal data bus at the same speed of the data bus and dynamic random access memory (RAM) coupled to and transmitting frames of data with a low speed local area network at the same speed of the low speed local area network. The SAM and RAM operate asynchronously with respect to each other to provide simultaneous bidirectional transfer of frames of data between them.

Abstract: A translation engine for translating frames of data from one frame format to another frame format in the same manner as an IEEE 802.1D MAC layer transparent bridge as required when transferring frames of data between interconnected heterogeneous local area networks. The translation engine is comprised of a variable length data pipeline capable of maintaining a constant synchronous data stream comprising frames of data from the input to the output of the data pipeline, without introducing any gaps in the data stream caused by removing fields of a frame, or causing the data stream to halt by inserting fields of a frame during translation of a frame from one frame format to another frame format.

Abstract: Multicast and broadcast frames transmission rate logic limiting the rate at which multicast or broadcast frames are forwarded by a MAC layer device interconnecting local area networks such as a bridge or switching hub, so as to prevent multicast or broadcast storms from propagating from one local area network to another local area network. Such logic is distributed among a plurality of local area network (LAN) ports of a switching hub, allowing the overall maximum rate at which such frames may be transmitted to be individually tuned on a per LAN port basis. The transmission rate logic includes a burst capability, in which the overall rate to which multicast and broadcast frames may be limited can be exceeded for a finite number of such frames. The burst capability may also be individually tuned on a per LAN port basis.

Abstract: A translation engine for translating frames of data from one frame format to another frame format in the same manner as an IEEE 802.1D MAC-layer transparent bridge as required when transferring frames of data between interconnected heterogeneous local area networks. The translation engine is comprised of a variable length data pipeline capable of maintaining a constant synchronous data stream comprising frames of data from the input to the output of the data pipeline, without introducing any gaps in the data stream caused by removing fields of a frame, or causing the data stream to halt by inserting fields of a frame during translation of a frame from one frame format to another frame format.