At&t Bell Laboratories

At+t Corp.

Vikram Punj

Ronald A Spanke

Rolfe E Buhrke

Kai Y Eng

Robert B Dianda

Mark A Pashan

Gary D Martin

Dennis L DeBruler

Alessandro L Isidoro

Albert Kai-sun Wong

Nancy S Stevens

Line cards provide an input/output interface between synchronous communication channels and an asynchronous network. An input line card generates a plurality of packets where each packet contains information carried by a group of synchronous communication channels; each synchronous communication channel of the group having a destination of the same output line card. A mechanism is provided for selecting a sequence for the sequential transmission of packets from the input line cards to the asynchronous network. The selecting mechanism minimizes the probability that a plurality of the input line cards will concurrently transmit a packet to the same output line card thereby creating a collision of packets requiring that all but one of the colliding packets be stored in a queue. Thus, minimizing collisions also minimizes queuing delays.

Telecommunication system with synchronous-asynchronous interface

Line cards provide an input/output interface between synchronous communication channels and an asynchronous network. The input line card translates information received from the synchronous communication channels into packets for transmission to the asynchronous network. Each line card generates and stores packets corresponding to a time frame associated with the synchronous communication channels. A sequence is selected for the sequential transmission of packets by each input line card to the asynchronous network. The cumulative number of packet collisions that would occur at each output line card during the predetermined time frame is determined. If the cumulative number of collisions exceeds a predetermined delay threshold, the number of packets actually transmitted to the system is reduced preferably by denying service to new call origination requests. This technique keeps the maximum cumulative collisions for each output line card within the predetermined delay threshold.

Telecommunication system with detection and control of packet collisions

An arrangement for pooling service circuits so that they become available to a plurality of switching systems in a telecommunications network. A regional control node receives a request for a service circuit to be connected to a call. The regional control node maintains the availability status of the service circuits in a pool for the region. In response to a request for a service circuit, the regional control node selects an appropriate circuit and transmits order to the switches and the circuit to establish the proper connections among these units in order to associate the service circuit with the requesting call. Advantageously, such an arrangement permits a large pool of individually expensive service circuits to serve a large number of switching systems, thus, increasing the efficiency of utilization of these service circuits. The arrangement is also used for controlling the allocation of transmission resources to any call, thus optimizing the use of the regional transmission resources.

Service circuit allocation in large networks

A data stream is converted from a synchronous transfer mode (STM) to an asynchronous transfer mode (ATM) by extracting data of a number of payload signals from the data stream, writing data of the payload signal into a random access memory (RAM), separately recording address locations of the data of each of the payload signals in separate buffers, directing the RAM to separately read the data of the payload signals, and attaching a cell header to the data read from the RAM to form ATM cells.

STM-to-ATM converters

This invention relates to methods and apparatus for interfacing between computer channels and a Broadband Integrated Services Digital Network (B-ISDN) in order to allow such channels to communicate with a large number of other channels over the long distances and large bandwidth provided by B-ISDN. In a terminal adapter, channel addresses are translated into network addresses and channel format data is converted into B-ISDN format data in order to allow data messages between channels to be transmitted over the B-ISDN network.

Channel adapter for broadband communications at channel speeds

This invention relates to a method and apparatus for determining which bus should be used for transmitting data to another station of a dual queue, dual bus DQDB network. Initially, data is transmitted over both buses. As each station receives an entity of data, such as packets or cells, over one bus, each entity including the identification of a transmitting station, the receiving station updates its memory to record that entities of data to that transmitting station should be transmitted over the other bus. The bus selection record is audited when packets are received to confirm its accuracy.

Initialization of data stations on a dual bus data subnetwork

This invention relates to a method and apparatus for controlling overload in a data network. The exemplary embodiment is a Broadband Integrated Services Digital Network (B-ISDN) in which data is transmitted within data cells included in a larger data frame using the Asynchronous Transfer Mode (ATM) protocol. In response to the network detecting overload, the network sends slow down messages to selected virtual channels to decrease their data rates. The network also acts to block or decrease resource allocations to transmission requests that are likely to overload the network.

Bandwidth and congestion management in accessing broadband ISDN networks

The invention relates to methods and apparatus for regulating traffic in a Broadband Integrated Services Digital Network (B-ISDN). Terminal adapters interface between terminals and the B-ISDN. Whenever a first terminal wishes to transmit a data message to a second terminal, the source adapter, connected to the first terminal, allocates transmit bandwidth for the transmission of the message and sends a request message to a destination adapter, connected to the second terminal, for checking availability of and allocating receive bandwidth. The data message is sent only if bandwidth has been allocated on both ends. Overflow traffic is throttled at the adapters before it enters the network, thereby reducing the number of data cells lost because of the limited storage of the network.

Arrangement for regulating traffic in a high speed data network

This invention relates to a method and apparatus for transmitting constant and variable bit rate traffic in a broadband ISDN switch. Data from constant bit rate sources such as television cameras is entered into a group of queues. Each member of the group for queuing data of a different band of bit rates. Data is transmitted from these queues with highest priority from the queue storing data of the highest band of bit rates. If the longest enqueued entity of data in one of the other queues has been enqueued for more than a prespecified period, its priority is increased. Analytic studies have shown that use of three queues for constant bit rate traffic and a fourth queue for variable bit rate traffic allows a high occupancy in the output channels to be maintained with a negligible number of data entities excessively delayed.

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Naperville, IL, United States of America

Vikram Punj