3com Corporation

Bruce W Mitchell

Mark S Isfeld

Michael J Seaman

Tracy D Mallory

Nagaraj Arunkumar

John H Hughes

Pyda Srisuresh

Greg Walter

James S Cho

Roger D Rothhaar

A communication technique for high volume connectionless-protocol, backbone communication links in distributed processing systems provides for control of latency and reliability of messages transmitted. The system provides for transmit list and receive list processes in the processors on the link. On the transmit side, a high priority command list and a normal priority command list are provided. In the message passing process, the command transmit function transmits commands across the backplane according to a queue priority rule that allows for control of transmit latency. Messages that require low latency are written into the high priority transmit list, while a majority of messages are written into the high throughput or normal priority transmit list. A receive filtering process in the receiving processor includes dispatch logic which dispatches messages either to a high priority receive list or a normal priority receive list. The filtering function also acts to drop messages received according to the amount of available buffer space in the receiving processor, as measured against watermarks based on reliability tags in message headers. The messages received are routed to either the high priority receive list or a normal priority receive list based on another control bit in the message headers. The receiving processor processes the messages in the receive queues according to a priority rule that allows for control of the latency between receipt of a message, and actual processing of the message by the receiving processor.

High throughput message passing process using latency and reliability

A high performance scalable networking bridge/router system is based on a backbone communication medium and message passing process which interconnects a plurality of input/output modules. The input/output modules vary in complexity from a simple network interface device having no switching or routing resources on board, to a fully functional bridge/router system. Also, in between these two extremes input/output modules which support distributed protocol processing are supported. A central internetworking engine includes a shared memory resource coupled to the backbone. The architecture includes a physical layer communication system for transferring control messages and data packets across the backbone, a logical layer interprocessor messaging system which operates over the physical layer across the backbone for communication between intelligent input/out modules, and between such modules in the central internetworking engine, and distributed protocol modules which are supported on intelligent input/output modules, and communicate using the logical interprocessor messaging system with the central internetworking resources.

Bridge/router architecture for high performance scalable networking

A bus protocol technique removes the transaction used for posting indications of events to the host processor from the bus. The invention takes advantage of the fact that addresses typically on a high speed bus contain fewer bits than the entire bus width. Particularly, for a 32 bit bus, the 32 bit address space is not always necessary. The remaining bits on the bus are used for an encoded event tag. A bus transaction involves a first bus transfer which provides an address for writing or reading data, along with the event tag. The event tag is detected and decoded by the destination, and the event is posted to the processor which monitors and responds to events, in a manner which is synchronous with completion of the transaction. Thus, after the transaction on the bus, the message subject of the transaction is waiting in the memory, and notification of the event has occurred automatically and synchronously with completion of the transfer.

Synchronous event posting by a high throughput bus

A tri-state synchronous bus driver avoids contention between succeeding cycles by shutting off each device's output enable early, so that it is guaranteed to no longer drive the line by the time any other device begins to drive. Enable activation occurs on a leading edge of the bus clock, and deactivation occurs at a delayed half phase clock edge. A low current bus holding cell is coupled to each bi-directional line to maintain the driven signal value until it can be sampled by a receiving device. This has the advantages that set up time is not eroded by the technique, and that the disable timing is relatively non-critical. The technique is particularly useful in gate array technology as process, temperature, and voltage variation can cause considerable fluctuation in the actual timing of circuits.

Driver for tri-state bus

A system uses a message passing paradigm for transferring large amounts of input/output data among a plurality of processors, such as a network intermediate system or router. A bus interconnects the plurality of processors with a plurality of bus interface devices. The bus interface device which originates a transfer includes a command list storing lists of commands which characterize transfers of data messages from local memory across the bus and a packing buffer which buffers the data subject of the command being executed between local memory and the bus. A bus interface device which receives a transfer includes a free buffer list storing pointers to free buffers in local memory into which the data may be loaded from the bus, and a receive list storing pointers to buffers in local memory loaded with data from the bus. The command list includes a first high priority command list and a second lower priority command list for managing latency of the higher priority commands in the software of the processor. The bus interface which receives the transfer includes control logic which manages data transfer into and out of an inbound buffer, including receiving burst transfers of message transfer cells from the bus, loading free buffers in local memory from the inbound buffer with message transtar cells, and updating the receive list. The receive list includes a first higher priority receive list and a second lower priority receive list for reliability management, and logic which monitors the free list so that lower priority messages may be dropped to prevent overflow of free buffer resources.

Network intermediate system with message passing architecture

An internetwork device which manages the flow of packets of I/O data among a plurality of network interface devices includes a bus coupled to the plurality of network interface devices, a core memory storing only packets of I/O data and control structures needed by the plurality of network interface devices, and a processor including local memory isolated from the core memory storing routines and internetwork information involved in updating control structures and control fields in the packets of I/O data to direct movements of packets of I/O data among the plurality of network interface devices. A bus-memory interface is provided through which transfers of packets of I/O/data and control structures used by the plurality of network interface devices are conducted between the core memory and the bus. A processor-memory interface is provided through which transfers of data to or from control structures or control fields in packets of I/O data are conducted between the core memory and the processor. Finally, a processor-bus interface is included through which configuration information concerning control structures and I/O data buffers in the core memory are transferred between the plurality of network interface devices and the processor across the bus. The processor-bus and processor-memory interfaces include structures for decoupling processor accesses to configuration stores in the plurality network interface devices and to the core memory from contention with bus-memory interface transfers between the core memory and the plurality of network interface devices.

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San Jose, CA, United States of America

Bruce W Mitchell