Fujitsu Corporation

Fujitsu Network Communications, Inc.

Jae Park

Roy McNeil

David Delgadillo

Michael J Samori

Jon Allingham

Bruce Pietsch

A communications network employs an optical communications medium carrying a synchronous communications transport signal including a number of time-division-multiplexed (TDM) channels. A number of bridges include respective interfaces to associated local area network (LAN) segments, and the bridges are coupled to the communications medium by associated add-drop circuits. Each add-drop circuit groups the TDM channels of the transport signal into bundles, each bundle being associated with a different bridge. Each add-drop circuit transmits data traffic originated by the associated bridge on only the bundle associated with the bridge, receives data traffic from the other bridges via the bundles associated with the other bridges, forwards the received data traffic to the associated bridge, and re-transmits at least some of the received data traffic on the bundles for receipt by another of the add-drop circuits.

Full multicast connectivity over SONET

A communications network includes a communications medium with a synchronous communications transport signal including time-division-multiplexed (TDM) channels, bridges having respective interfaces to different local area network (LAN) segments, and add-drop circuits coupling associated ones of the bridges to the communications medium. Each add-drop circuit groups TDM channels of the communications transport signal into a bundle, and schedules the use of the bundle to carry data traffic originated by the associated bridge and to carry data traffic originated by the other bridges. Data traffic originated by the associated bridge and destined for the other bridges is transmitted on the bundle in accordance with the scheduling. For data traffic received from the other bridges via the bundle, it is determined whether the received data traffic is destined for the associated bridge, and if so then it is forwarded to the associated bridge. Receieved data traffic destined for the other bridges is re-transmitted on the bundle in accordance with the scheduling for receipt by the add-drop circuit associated with the destination bridge.

Shared VT connectivity over SONET

A network device transfers variable-length data frames across a synchronous network employing a multiple-channel synchronous transport signal. Encapsulation logic encapsulates each data frame in a point-to-point frame including a body portion of the data frame and a length value located in a beginning portion of the point-to-point frame. Segmentation logic divides each point-to-point frame into fixed-sized segments, a first segment carrying the beginning portion of the point-to-point frame. Transmitting circuitry transmits the frame segments as payloads of at least one channel of the synchronous transport signal, the payloads being marked so as to be identifiable. Receiving circuitry receives payloads of at least one channel of the synchronous transport signal and from each received set of payloads regenerates a corresponding point-to-point frame using the length value from the first segment thereof. De-capsulation logic de-capsulates each regenerated point-to-point frame to recover the corresponding data frame.

Transmission of data frames using low-overhead encapsulation and multiple virtual tributaries in a synchronous optical network

A congestion control mechanism in an ATM network access device includes segmentation and reassembly (SAR) logic that sends and receives Asynchronous Transfer Mode (ATM) cells to and from interface logic that transfers the cells to and from a switch fabric. The cells are transferred on ATM connections, including flow-controlled connections for which the sending of cells by the SAR logic is controlled in response to the settings of Generic Flow Control (GFC) bits appearing in the headers of ATM cells received by the SAR logic. The interface logic receives a congestion signal indicative of the level of congestion in a transmit buffer in the switch fabric. In response to the congestion signal, the interface logic sets the GFC bits in the headers of cells transferred to the SAR logic such that the cell transmission rate is maintained at a high average level while undesirable congestion in the transmit buffer is avoided. Hysteresis is employed in the setting of the GFC bits is response to the congestion signal. The interface logic generates idle cells during periods in which no traffic-carrying cells are being transferred from the switch fabric to the SAR logic, and sends the idle cells to the SAR logic to provide GFC signalling during such periods.

Congestion control mechanism in a network access device

LAN interface logic ( ) receives frames from a LAN segment ( ), and frame transport logic ( ) transfers frames to and from an ATM network. Forwarding logic ( ) is used to (i) determine whether a mapping between a destination address (DA) and a virtual connection (VC) in the ATM network exists, (ii) forward frames containing a known DA to the frame transport logic for transfer to the ATM network, (iii) forward frames containing unknown DAs to the frame transport logic for transfer to a broadcast and unknown server (BUS ) in the ATM network, and (iv) pass unknown DAs to a LAN emulation client (LEC) processor ( , FIG. ) to resolve the address. The LEC processor creates a LAN emulation address resolution protocol (LE_ARP) request message containing the unknown DA, and the LE_ARP request message is transferred to a LAN emulation server (LES ). The LES returns an ATM address of a remote LEC via which the destination node can be reached. The LEC processor uses the ATM address to establish a new VC to the destination node, and provides the DA-VC mapping to the forwarding logic for use in forwarding subsequently received frames.

Interface to network protocol software to support hardware acceleration of critical functions

A network access device includes a cell buffer memory ( ) and segmentation and reassembly (SAR) logic ( ) between multiple local area network (LAN) interface logic blocks ( ) and logic ( ) interfacing with a cell-based network such as ATM. The cell buffer memory can be programmably partitioned into distinct buffer regions, each being associated with a respective LAN and with a respective set of virtual connections on the cell-based network. The SAR logic segments received frames into groups of cells, stores each group of cells into the buffer region associated with the respective LAN, and transfers the groups of cells from each buffer region to the cell-based-network interface logic via the associated virtual connections. The SAR logic and the cell memory are shared among multiple LAN bridges implemented by the LAN interface logic blocks and the cell-based-network interface logic, while traffic from the different bridges is kept separate. The SAR logic also manages the network bandwidth assigned to the different bridges separately, so that traffic from one bridge generally does not affect another bridge's use of its allocated bandwidth.

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Congers, NY, United States of America

Jae Park