Abstract: In an ATM network interface controller, a traffic management system is provided to allow implementation of available bit rate, or ABR, flow control by an external processor and the use of a new ABR controller within the traffic management system which provides functions that enable an external processor to control the flow control behavior of the network interface controller. The ABR controller accesses an external memory to control the flow of cells injected into the network. In one embodiment, the subject system uses a traffic shaper to control cell transmission rates, submits requests to an external memory which are processed by an external processor, and reads data from an external memory to adjust cell transmission rates and/or generates Resource Management, or RM, cells.

Abstract: A switch for digital communication networks includes a queuing system cape of implementing a broad class of scheduling algorithms for many different applications and purposes, with the queuing system including both a tag-based primary queue which contain ATM cells organized by priority and a secondary queue which contains ATM cells which are not yet scheduled for transmission and which are organized by virtual channel. A queuing decision module is provided to determine in which queue an incoming ATM cell should be deposited. A requeuing module operates when an event occurs that unblocks a particular virtual channel. The requeuing module, on occurrence of such an event, accesses the secondary queue to obtain another cell, to assign it priority and to move it to the primary queue. The queuing decision module, along with a virtual channel table, can be used easily to block virtual channels when necessary. The combination of queues also allows for round robin scheduling.

Abstract: In an ATM network, a traffic shaping system is provided with a number of timing subchains each having slots at which cells are queued and each having a pointer to specify the readout of cells at a slot. The system eliminates the necessity for providing large numbers of slots for low data rate traffic while at the same time accommodating high data rate transmission by moving pointers for low data rate traffic at slower rates than pointers for higher data rates. In one embodiment, this is accomplished by increasing the time scale for slots far away from the current time by moving the time pointer increasingly slower for ever more distant slots. When a pointer is at a slot, cells queued at this slot are moved to a slot in the next prior subchain, with cells in the top subchain transmitted when selected by the associated pointer.

Abstract: A system for controlling traffic in a digital communication network to avoid data loss due to congestion utilizes both credit-based and rate-based traffic control approaches within a common framework, and adjusts the rate at which data is transmitted from a source in accordance with feedback in a form of credit values from a destination reflecting the ability of the network to transmit data and the destination to receive data. In one embodiment, the destination receives the information about network congestion, and, knowing its own capacity to receive more data, generates a credit in the form a numeric value which is fed back to the source so that the source adjusts its transmission rate to avoid data loss due to congestion in the network.

Abstract: A system is provided for generating the minimum synchronous bandwidth allocation h.sub.i for token ring networks in which this minimum bandwidth allocation is utilized by the node to request appropriate synchronous bandwidth reservation from the network manager. This permits the synchronous bandwidth allocation h.sub.i to be set dependent upon the minimum message generation period, T, the maximum message transmission time, C, the requested message delivery delay bound, d, and the target token rotation time of the network, TTRT. The system is not limited to d=T as is common in prior systems, but rather accommodates any value of d. As a result, the system is both simpler to implement, and covers many more applications having different message delivery time constraints. The calculation of h.sub.i is done by ensuring that the time that a node is allowed to transmit messages in the worst-case is no smaller than the time that the node needs to satisfy the message delivery time constraints.

Abstract: A method and apparatus for improved data communications over a token ring interface in which a target token rotation time value is a function of an initial target token rotation time value, the summation of the high priority token holding times for each node on the ring, and the time required to transmit a maximum size packet. Furthermore, the target rotation timer for the token ring network is activated only when the node is not transmitting in a synchronous manner.