Abstract: A system and method for adding routing information for a node to a routing table, which efficiently makes necessary changes to the routing table to support routing to and from the node, while maintaining the deadlock-free quality of the paths described by the routing table. The routing table is generated by storing routing information in the routing table that reflects and describes a deadlock-free set of paths through a network of nodes. A row of entries is added to the routing table describing how to forward data units from the node. A column of entries is added to the routing table describing how to forward data units addressed to the node. The forwarding information within each entry added to the routing table maintains the deadlock-free quality of the set of paths represented by the forwarding table.

Abstract: A system for selecting routing information from a routing table describing alternative routes between end nodes. The routing table represents a set of minimum cost, deadlock-free routes between end nodes. The selected routing information is included in forwarding tables, and sent to networking devices in the network. The selected routing information is optimized for at least one network performance metric, such as overall network capacity or fault tolerance. Capacity optimization is obtained by selecting from alternative routes stored within the routing table such that the standard deviation of the number of routes flowing over each link in the network is minimized. Fault tolerance optimization is achieved by selecting from the alternative routes stored in the routing table such that the selected route for a given end node pair has a “failover” route with a maximum number of dissimilar links from the selected route.

Abstract: A distributed system and method for generating “layered routes.” The layered routes generated by the disclosed system reflect a layered representation of the network. By operating in accord with the layered representation of the network, the disclosed system provides deadlock-free routes. The layered representation consists of an ordered set of layers, where each layer is a deadlock-free sub-topology of the network. In determining routes using links from different layers, the links used in each route are constrained to be taken from layers of non-decreasing order as the route extends from source to destination.

Abstract: A method and apparatus that constructs a “router database” and then uses the database to determine a longest match between a piece of target data, such as an address in a packet to be routed, and the database. The database contains a comparison table having a plurality of entries. In a first embodiment, each entry has up to k values, where 2<=k<=N, where N is a number of comparison values in the database. In a second embodiment, each entry has up to k−1 values. During operation, various ones of the comparison table entries are loaded and compared to the address to determine a longest matching prefix in the router database. The comparison can be done in parallel.

Abstract: A method of detecting congestion in a computer network uses a receiving station which determines a first number of messages missing in a first acknowledgment window. The station then determines a second number of messages missing in a subsequent acknowledgement window. The station then measures congestion on the network in response to an increase in the number of missing messages as indicated by the first number of missing messages in the first acknowledgement window and the second number of missing messages in the second acknowledgement window.

Abstract: Receiver stations located close together in a computer network dynamically form a multicast repair tree by a plurality of receiver stations choosing a repair head station from among the closely located receiver stations. A receiver station calculates its distance from a repair head station by subtracting the decremented TTL value read from the IP header from the initial value of the TTL parameter carried in field TTL SCOPE of HELLO messages, transmitted by repair head stations. Using a criteria that a closer repair head station is a more optimum repair head station, receiver stations listen to each received HELLO message, calculate the distance to the repair head station, and reaffiliate with the closest repair head station.

Abstract: A multicast repair tree is established, the repair tree having one sender station and a plurality of repair head stations. A repair head station has an affiliated group of member stations. A repair head station retransmits a lost message to its affiliated group of member stations upon receipt from a member station of a NACK message indicating that the selected message was not received. Acknowledgment windows (ACK windows) are established in a member station for transmission of ACK or NACK message by the member station. A number of messages transmitted by the sender station during a transmission window is established. Also a same size of ACK window is established in the receiving stations, with a slot in the ACK window corresponding to each message transmitted by the repair head station. Each receiving station is assigned a slot in the ACK window during which time that receiving station transmits its ACK or NACK messages.

Abstract: To authenticate and authorize prospective members in a reliable multicast data distribution setup, the prospective members contact a central authority to obtain a “participation certificate” for the multicast session. The central authority authenticates each node and issues a digitally signed certificate to the node. Each certificate contains information specifying the manner in which the respective node is authorized to participate in the multicast session in addition to the respective node's public key. The nodes exchange their participation certificates with each other during session-establishment dialog to prove their identities and their authorization to participate. Each node verifies the rights of other nodes based on authorization information contained in the participation certificate received from the other node. Thus, a node is allowed to participate as a repair node only if it presents a participation certificate authorizing it to do so.

Abstract: A method and system for pruning slow multicast group members in a multicast group that includes a sending node and member nodes. The sending node and selected ones of the other nodes comprise repair heads of a repair tree. Each repair head has at least one child. Each of the member nodes generates a slowness metric. Each member node repair head aggregates its own slowness metric with the slowness metrics of their respective children in the tree along with a subtree flag that indicates whether the respective slowness metric is due to the reporting node or a node downstream of the reporting node. The member node repair heads propagates the largest of the aggregated slowness metrics upstream along with a subtree flag associated with the propagated slowness metric. Via this process the sending node receives the largest slowness metrics generated in respective branches of the repair tree along with corresponding subtree flags associated with the respective metrics.

Abstract: A base node of a computer network sends concurrent TTL query messages using multicast to other receiving nodes of the computer network. Each of the TTL query messages has a different time-to-live (TTL) parameter value and records the TTL parameter of the TTL query message into a message body. The receiving nodes receive one or more of the TTL query messages, namely, those TTL query messages whose TTL parameter values are sufficient to allow the TTL query message to reach the receiving node. Each receiving node can determine the TTL distance to the receiving node from the base node by determining the lowest TTL parameter value of all TTL query messages which reached the receiving node. Each receiving node communicates the TTL distance by sending to the base node a TTL query response message which indicates, in the message body, the least TTL parameter value of all TTL query messages received by the receiving node.

Abstract: An embodiment consistent with the present invention includes a method and apparatus for forming a multicast repair tree. The method may be performed by a data processor and comprises the steps of determining, for each of a plurality of potential heads in a multicast group, a ranking value associated with the potential head; advertising, by the potential heads to a plurality of potential receivers; prioritizing, by a potential receiver, the ranking values from the potential heads; and binding, by a potential receiver to the head having the highest ranking value, thereby forming a group of which the potential receiver is a member and the potential head is the head. The head may also be the sender. There may be a plurality of heads. The ranking values may include “able”, “unable”, “willing”, and “reluctant.” The ranking value of a potential head may be determined in accordance with a static or a dynamic configuration.

Abstract: In a digital data network, a plurality of devices interconnected by a communication link organize themselves into a tree structure. Each of the devices has an associated suitability value that generally relates to the device's suitability for becoming a node in the tree structure. The devices organize themselves into a tree structure in one or more iterations, each iteration comprising two general steps, namely, a node election step and a tree establishment step. In the node election step, the devices whose suitability values are such that they can become nodes in the tree broadcast over the communication link node election messages including their respective suitability values. These devices also receive the node election messages that are broadcast by other devices. Each device determines whether it is elected a node in the tree structure in connection with a comparison between its suitability value and suitability values of node election messages received thereby.

Abstract: Method and apparatus for operating a digital communication network to avoid congestion by detecting load conditions at intermediate stations exceeding an overload condition, and flagging information packets associated with those streams of traffic accounting for more than their fair share of throughput at such overloaded stations.

Abstract: Method and apparatus for operating a digital communication network to avoid congestion by detecting load conditions at intermediate stations exceeding an overload condition and adjusting the rates at which source stations that are utilizing more than their fair share of throughput capacity transmit information through the intermediate stations.

Abstract: Method and apparatus for operating a digital communication network to avoid congestion by detecting load conditions at intermediate stations exceeding an overload condition, flagging information packets associated with those streams of traffic accounting for more than their fair share of throughput at such overloaded stations, and reducing at the end systems the throughput of those streams of traffic of which more than a predetermined fraction of the information packets received by the end systems are flagged.

Abstract: Method and apparatus for operating a digital communication network to avoid congestion by detecting load conditions at the routers exceeding their knee capacities, flagging information packets associated with those streams of traffic accounting for more than their fair share of throughput at such overloaded routers, and reducing at the end systems the throughput of those streams of traffic for which more than a predetermined fraction of information packets received by the end systems are flagged.

Abstract: A method is used for collecting information at the session level for a multiple node distributed processing system. A first component software program monitors all packets passing through a node and extracts packet headers having a predetermined format from all nodes. A second component software program identifies a session in which each of the extracted packet headers was transmitted and, for each session, accumulates characterizing information about that session and calculates statistical data concerning all the sessions.