International Business Machines Corporation

Raif O Onvural

Gerald Arnold Marin

Vijay Srinivasan

Allen Leonid Roginsky

Mohammad Peyravian

Ken Van Vu

James P Gray

Roch A Guerin

Gerald Lebizay

Gary Roy Shippy

Ling-Ching W Tai

Caglan M Aras

Claude R Galand

Lap Thiet Huynh

Aline Fichou

Levent Gun

Bouchung Lin

Serge Fdida

Erol Gelenbe

Xiaowen Mang

Methods, systems and computer program products for controlling scheduling in an ATM node in a network are provided which aggregate connection information for connections to the ATM node to provide a set of aggregate connection information for the ATM node. The set of aggregate connection information is distributed to other ATM nodes in the network and may be used in accepting connections to the ATM network based on the aggregate connection information. Scheduling may be provided by associating a timestamp value in each cell associated with an accepted connection as it is received by the ATM node. Received cells are grouped into a plurality of cell groups in timestamp order based upon characteristics of the cells and cells are selected from each group so as to transmit the cells in earliest deadline first order.

Systems, methods and computer program products for distributing connection information between ATM nodes

Methods, systems and computer program products are provided for evaluating requests for a network connection combining the requested network connection with existing connections so as to provide a representation of the total network connections and accepting the request for a network connection if sufficient resources are available to accept the request for a network connection based upon the representation of the total network connections. Particular embodiments of the present invention determine if sufficient resources are available to accept the request for a network connection based upon diffusion based representations of the existing network connections and the requested network connection and accepting the request for a network connection if sufficient resources are available to accept the request for a network connection. The diffusion based representation may be used to determine the capacity required for existing connections and the requested connection based upon a predefined maximum loss ratio (L).

Statistical call admission control

Systems methods and computer program products for controlling earliest

Methods, systems and computer program products which identify network routing paths having a first performance characteristic less than a first specified limit and a second performance characteristic less than a second specified limit from a plurality of routing paths. These routing paths are identified by combining both the first performance characteristic and the second performance characteristic for one of the plurality of routing paths to provide a third performance characteristic which differs from both the first and the second performance characteristic and which operates as a proxy for the first and second performance characteristic. It is then determined if the third performance characteristic of the routing path is less than a third performance limit associated with the third performance characteristic.

Selection of routing paths in data communications networks to satisfy

An apparatus and method allow two or more members of a network, connected in multipoint-multipoint manner, to synchronize their local service clocks. Overall synchronization is achieved as soon as every member within the network transports its own timing information to other members of the group, plus the maximum propagation delay between the group members, and accordingly minimizes the possibility of overruns and underruns at each node end. Such synchronization is implemented when all members of a network synchronize their internal clocks to a lowest clock frequency within the network.

Recovering a clock signal in a multimedia network using time stamps

An enhanced adaptive rate-based congestion control system for packet transmission networks uses the absolute rather than the relative network queuing delay measure of congestion in the network. Other features of the congestion control system include test transmissions only after a predetermined minimum time, after the receipt of an acknowledgment from the previous test, or transmission of a minimum data burst, whichever takes longest. The congestion control system also provides a small reduction in rate at low rates and a large reduction in rates at high rates. A logarithmic rate control function provides this capability. Rate damping is provided by changing all of the values in a rate look-up tables in response to excessive rate variations. Finally, the fair share of the available bandwidth is used as the starting point for rates at start-up or when a predefined rate damping region is exited.

Adaptive rate-based congestion control in packet networks

An explicit rate algorithm is disclosed for use in an end-to-end closed loop flow control algorithm for an ATM network which carries at least constant bit rate (CBR) traffic, variable bit rate (VBR) traffic and adjustable bit rate (ABR) traffic. The algorithm determines how much additional bandwidth is available for ABR traffic on an output link from a node and produces an explicit rate variable that can be forwarded to a source for the ABR traffic. Both the maximum and minimum bandwidths already reserved for all connections on the output link are determined. A single reserved bandwidth value is chosen within the range defined by the maximum and minimum reserved bandwidth values. The current utilization of the ABR input buffer for the node is also determined. The explicit rate variable is generated as a function of the link capacity, the reserved bandwidth value and the current utilization of the ABR input buffer. The explicit rate variable is written into a resource management cell which is routed through the network to the ABR traffic source. The explicit rate variable is intended to change the input rate of the ABR source to utilize more of the ABR input buffer.

ATM network congestion control system using explicit rate cell marking

A distance learning system consists of a plurality of multi-cast clients of various classes and priorities with one multi-cast client as a primary multi-cast client, a multi-cast server, arbitrator and a distance learning session coordinator. The primary multi-cast client provides the default or primary Audio-Visual Material (AVM) stream. The Multi-Cast Server (MCS) setups a multi-cast over a point to multi-point connection which connects all multi-cast clients that are to take part in a particular distance learning session, along with the Primary multi-cast client. Additionally, the primary multi-cast client is connected to the MCS via a point-to-point link. The multi-cast clients and the primary multi-cast client receive an AVM material stream from the multi-cast server via the point to multi-point connection. When a multi-cast client wishes to speak, a speaking request is sent to the arbitrator, the arbitrator determines whether to grant or deny the speaking request. If permission is granted then a point-to-point link is established between the requesting multi-cast client and the MCS. The requesting multi-cast client then provides an AVM stream to the multi-cast server over the newly established point-to-point connection and the multi-cast server switches or provides the AVM stream associated with the requesting multi-cast Client over the point to multi-point connection. When the requesting multi-cast client is through speaking the MCS switches the AVM stream associated with the primary multi-cast client onto the point to multi-point connection and the point-to-point link with the requesting multi-cast client is terminated.

Method and apparatus for multi-cast based video conferencing

Method system and article of manufacture for multi-casting audio visual

To enhance the security provided by data encryption in a data communication network, the encryption/decryption keys are changed periodically at the source and destination nodes for an established connection. A destination node must know not only the value of any new key but also when to begin using that key to decrypt received data packets. Synchronization (making sure a data packet is decrypted using a decryption key correlated with the encryption key used to encrypt the same packet) is achieved by defining a single bit in each packet header as a key synchronization bit. As long as key synchronization bit value remains unchanged from one received packet to the next, a receiving node will continue to use the same decryption key it has been using. When a change in the key synchronization bit value is detected, the receiving node will begin using a previously-received, new decryption key.

Synchronization of encryption/decryption keys in a data communication

To enhance the security provided by data encryption in a data communication network, encryption/decryption keys are changed periodically at the source and destination nodes for an established connection. A destination node must know not only the value of any new key but also when to begin using that key to decrypt received data packets. Synchronization (making sure a data packet is decrypted using a decryption key correlated with the encryption key used to encrypt the same packet) is achieved through the use of marker cells, which are special purpose cells. When a source node decides to activate a new key, previously sent to and stored at the destination node, a marker cell is transmitted by the source node to the destination node. When the destination node recognizes the marker packet, it discards it and activates the previously received key for use in decrypting subsequently received packets.

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Cary, NC, United States of America

Raif O Onvural