At&t Bell Laboratories

American Telephone & Telegraph Co., At&t Bell Laboratories

Charles R Kalmanek

Alexander Gibson Fraser

Robert H Delaney

Robert C Restrick, Iii

Srinivasan Keshav

Ellen L Hahne

Samuel P Morgan

Apparatus and methods for time multiplexing a resource among a plurality of entities at average rates and with deterministic delays between accesses to the resource by an entity. An entity accessing the resource receives a time slot on the resource; a fixed number of time slots constitute a frame. Each entity receives a fixed allocation of time slots in the frame. When an entity has work for the resource to do, it receives access to the resource for a number of slots in each frame equal to the lesser of the number of slots required to do the work and the number of slots in the allocation. A rate-controlled server is disclosed which defines a frame and allocations therein, as well as a hierarchy of servers which combines rate-controlled traffic with best effort traffic. In the hierarchy, a rate-controlled server activates a round-robin server when the entities served by the rate-controlled server do not require all the slots in a frame. A hierarchy of rate-controlled servers is further disclosed which permits access to the resource at widely-differing average rates. In that hierarchy, a number of slots in the frame for a given member of the hierarchy are reserved for the next member down of the hierarchy and the next member down is active only during those slots. Further disclosed are nodes of ISDN networks employing ATM which incorporate the servers and hierarchies thereof.

Apparatus and method for time multiplexing a resource among a plurality

A method of controlling congestion in a virtual circuit packet network. A initial packet buffer is assigned to each virtual circuit at each node into which incoming packets are stored and later removed for forward routing. If a larger buffer is desired for a virtual circuit to service a larger amount of data, then additional buffer space is dynamically allocated selectively to the virtual circuit on demand if each node has sufficient unallocated buffer space to fill the request. In one embodiment, the criterion for dynamic allocation is based on the amount of data buffered at the data source. In alternative embodiments, the criteria for dynamic allocation may be further based on the amount of data buffered at each node for a virtual circuit and the total amount of free buffer space at each node of a virtual circuit. Signaling protocols are disclosed whereby data sources and virtual circuit nodes maintain consistent information describing the buffer allocations at all times.

Method and apparatus for congestion control in a data network

A local area data distribution system includes a plurality of data processing stations connected to a common bus. Individual data processing stations contend with each other for access to the bus while the bus is held at a predetermined and controlled but overridable logic state by applying their priority code bit by bit to the bus and comparing the logic state of the bus with the bit they are applying thereto. A biasing arrangement holds the bus at the predetermined and controlled logic state during the contention interval at a signal level that may be easily overridden by an output of any one of the individual data processing stations.

Local area network with biasing arrangement for facilitating access

In a local data distribution network configuration a plurality of bidirectional data distribution busses are each connected to a bus master control circuit at a terminal end of the bus. Connected to each of the data distribution busses are a plurality of passive outlets to which intelligent connectors or stations may be connected. Each station has a unique address and is utilized for individually coupling data processing devices to the bus. Grouped pluralities of the bus master control circuits are included within a bus termination hub facility. Data from any of the bus master control circuits may be transferred by the bus termination hub via a data trunk as part of a star type configuration, to a central switching circuit such as a virtual circuit switch. Direction of data flow on each of the bidirectional busses and periodic temporary synchronization of the stations is controlled in response to signals transmitted to the bus by the bus master control circuitry associated with that bus. A bus termination hub switching facility cooperates with the included group of bus master control circuits to interconnect data processing stations on the various busses with the virtual circuit switch via the trunk line and with each other. The bus termination hub facility further includes bus monitoring, status polling and maintenance facilities. A faulty bus will be disconnected if a fault is discovered during monitoring intervals. It will remain disconnected until the fault is corrected.

Growing community of inventors

Hoboken, NJ, United States of America

Charles R Kalmanek