Fujitsu Network Communications, Inc.

Robert H Constantin

Thomas A Manning

David N Peck

Stephen R Veit

David E Hammond

Mark A W Stewart

Shantnu Sharma

Peter W Bretschneider

Mashood Illikkal

Andrew Michal

Sajin R Valoth

Salma Abu-Ayyash

A highly available communications system capable of circuit reestablishment and tear-down without manual intervention. The communications system includes a plurality of nodes interconnected by a plurality of communications paths to form at least one communications network. The nodes forward control packets on the network by way of a signaling protocol employing an out-of-band control technique. At least a portion of the nodes comprises a software configuration including a topology manager and a protocol manager. The protocol manager is operative to determine whether a control path is operational and whether a data transmission channel along a corresponding data path is established. In the event the control path is not operational, the protocol manager maintains the data transmission channel along the data path so long as the channel is established. The topology manager is operative to acquire network topology data, and the protocol manager is further operative to receive the topology data, deduce network topology changes therefrom, and reestablish and tear-down communications paths interconnecting the nodes based at least in part on the deduced topology changes.

Circuit reestablishment and tear down in a highly available communications system

Each switch along a call setup path in a network decides whether the call request should be upgraded from a non-flow-controlled service type to a flow-controlled service type. Each switch bases the decision on whether a boolean variable for the calling subscriber that appears in a management information base (MIB) is set to a value indicating that the subscriber is entitled to the upgrade. In addition, the upgrade is performed only if an interface on the route to the called party on which the call setup request is to be forwarded supports flow-controlled connections. When the call is to be upgraded, the switch replaces the service type indicator in the setup message with a value indicating a flow-controlled service type, and forwards the setup message toward the called subscriber. If the MIB variable is set to a value indicating that the upgrade is not to be performed, it is still possible for a subscriber to request flow-controlled service directly, by indicating this service type in the original call setup message. Each switch also makes a call downgrade decision. When a call setup message is received requesting flow-controlled service but destined for an interface that does not support flow-controlled operation, the switch replaces the service type indicator in the outgoing setup message with a value indicating a non-flow-controlled service type.

Distributed control of service category request mapping

A system for allocating resources at network elements along a path through a communications network. Resources are allocated at a network element along the path in response to a connection request message. The delay budget is the minimum of a calculated cell transfer delay and a calculated cell delay variation. The calculated cell transfer delay is determined by finding a difference between a target end to end cell delay and an accumulated cell delay, and then dividing that difference by a number of network elements remaining in the path between the network element and the end of the path. To determine the calculated cell delay variation, the network element first finds a difference between the Max CDV QoS parameter and the sum of the accumulated cell delay variation and the switching delay for the network element. The calculated cell delay variation is then equal to that difference divided by the number of network elements remaining in the path between the network element and the end of the path. The target end to end cell delay is for example determined by the first network element in the path as equal to the Max CTD QoS parameter minus the end to end link propagation delay for the path and the link propagation delay for the incoming link to the first network element over which the message was received. The first network element generates and forwards a modified connection request message including the determined target end to end cell delay value, as well as a designated transit list indicating each network element in the prospective path, and including a current network element pointer.

Network element delay allocation for efficient use of network resources

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Cambridge, MA, United States of America

Robert H Constantin