Abstract: A local network system is provided using ATM-like framing and cells for data transmission. A bus architecture is defined, making the cost per port relatively low compared to matrix switching. For high performance, the bus is bit parallel instead of being a serial link. Like other LANs, the average bandwidth per interface (per port) is a low percentage of the peak bandwidth. A single physical bus is used to interconnect a potentially large number of ATM interfaces, on the order of hundreds. The system employs a bus master which provides timing and resolves all arbitration requests. Interfaces connected to the bus are allotted at least one cell per frame for sending data, and write to the allotted cell in synchronization with the frame, cell and bit clocks circulated on the bus from the master.

Abstract: A telecommunications network of the type having links with long propagation delay uses an asynchronous transfer mode in which small, fixed-length blocks of information (cells) are transferred at very high speed. Each long-haul hop within the network is phase-locked to a fixed period, and time slots of a granularity of one cell are pre-allocated to the virtual circuits. The network operates in a near-synchronous (plesiochronous) manner. By pre-allocating cells, it is assured that the cells will not arrive at a faster rate than that at which each receiving node can forward them on to the next hop. When bursts of heavy traffic occur, the network responds by slowing or limiting access, rather than by loss of data at intermediate nodes due to buffer overflow.

Abstract: A data communication network subject to bursty traffic employs a bandwidth allocation scheme to avoid congestion. When a source node has a burst of traffic to send, it first sends a bandwidth request message through the network from source to destination. At each intermediate node, this bandwidth request is examined and the node determines how much of the requested traffic level it will be able to support at a time in the future of one round-trip interval hence, and this node either grants the request or marks down the request to a level that it can support, then passes it on. When the request reaches the destination, it is returned along the same path to the source, and the source then employs the marked-down allocation to select the rate used to send the burst of data. The allocation for this source node remains in effect for a limited time, depending upon the amount of data to be sent in the burst, then returns to a "residual" level.