Abstract: Capacity design of an optical network for demands of connections forms a linear programming sizing problem for a optimal routing. A dual of the linear programming sizing problem is formed and solved with an approximation algorithm. Edge lengths are initialized based on i) the inverse of the edge's capacity and ii) a scalar constant. Then, the approximation algorithm proceeds in phases to route each commodity over the edges of a graph. During each phase, the demand's flow is sent from the source to destination via multiple iterations. During each iteration, the shortest length-bounded path from the source to the destination is determined, a portion of the flow is sent, and the lengths of the edges that carry the flow are updated. The value employed to scale the network is generated after the last phase from the maximum ratio of edge flow to edge capacity.

Abstract: A packet network employs restorable routing with service level guarantees. Restorable routing generates two disjoint paths through a network of nodes interconnected by links for a connection request demand between and ingress-egress node pair. Restorable routing employs minimum interference criteria to generate the two disjoint paths such that two disjoint paths cause little or no interference with demands of future connection requests between different ingress-egress pairs. Restorable routing generates maximum 2-route flows for the network ingress-egress node pairs to determine corresponding sets of 2-critical links. A reduced network is formed, its links are weighted based on criticality indices generated from the sets of 2-critical links, and the relatively optimal two disjoint paths are computed for the connection request. One of the two disjoint paths is selected as an active path for routing data of the connection request, and the other disjoint path is selected as the backup path.

Abstract: A switch schedules guaranteed-bandwidth, low-jitter-traffic characterized by a guaranteed rate table (GRT) method. A rate matrix generated from collected provisioning information is decomposed into schedule tables by a low jitter (LJ) decomposition method. The LJ decomposition method imposes a set of constraints for the schedule tables: schedule tables are partial permutation matrices, weighted sum of the partial permutation matrices is greater than or equal to the weighted sum of the rate matrix, and each entry in the rate matrix belongs to one element of the LJ decomposition schedule matrices. An integer LJ decomposition programming problem is employed to generate the schedule tables that are scheduled for each time slot of the period of the switch. Schedule tables are selected in turn based upon selecting eligible tables having the earliest finishing time. If necessary, the rate matrix is updated prior to decomposition for a subsequent period.

Abstract: Methods and systems for estimating the number of active connections in a node in a communications network are described. The node estimates the number of active connections, without maintaining state information on each connection in the node, by sampling one or more packets in a buffer in the node when the node receives a packet, determining the number of sampled packets that are associated with the same connection as the received packet, and estimating the number of active connections in the node based on the determined number of the sampled packets. The node stabilizes the number of packets in the buffer by estimating the number of active connections in the node based on a sampling of the packets in the buffer when the node receives a packet, determining a probability for discarding the received packet based on the estimated number of the active connections and the recent buffer occupancy, and discarding the received packet according to the determined probability.

Abstract: Apparatus for routing packets in a communication network comprises a plurality of per-connection queues, each queue established for receiving packets from a respective source and temporarily storing received packets before routing to a particular destination; a weighted fair-queuing scheduler for servicing packets from each of the plurality of per-connection queues at guaranteed pre-allocated rates; a sensing device for sensing a presence or absence of packets in queues, the absence of packets in queues indicating availability of excess bandwidth; and, a state dependent scheduler for redistributing excess bandwidth upon sensing of queues absent packets, the state dependent scheduler servicing those queues in accordance with a state variable corresponding to a performance property of the queues, wherein delay and isolation properties for routing packets of respective queues in weighted fair-queuing is preserved.

Abstract: A network element maintains failure information for a packet-based network and usage information for a backup path. Upon receipt of a new demand, with an associated bandwidth, d, the network element determines if the backup path can be shared as a function of the failure information and the usage information associated with the backup path.

Abstract: A packet network of interconnected nodes employs dynamic backup routing of a Network Tunnel Path (NTP) allocates an active and backup path to the NTP based upon detection of a network failure. Dynamic backup routing employs local restoration to determine the allocation of, and, in operation, to switch between, a primary (also termed active) path and a secondary (also termed backup) path. Switching from the active path is based on a backup path determined with iterative shortest-path computations with link weights assigned based on the cost of using a link to backup a given link. Costs may be assigned based on single-link failure or single element (node or link) failure. Link weights are derived by assigning usage costs to links for inclusion in a backup path, and minimizing the costs with respect to a predefined criterion. For single-link failure, each link in the active path has a corresponding disjoint link in the backup path.

Abstract: A network employs integrated, dynamic routing (IDR) of service level (e.g., bandwidth) guaranteed paths for network tunnel paths (NTPs), such as Internet Protocol (IP) packet connections, through an optical network, such as a wavelength division multiplex (WDM) optical network. For example, IDR accounts for both optical network topology (e.g., optical switches and crossconnects as well as the links between nodes) and resource usage information (e.g., the available/provisioned link bandwidth and available/used wavelength paths). The topology and usage information may be available from the IP and optical WDM protocol layers. IDR determines several aspects of routing for an arriving request for a network tunnel path (e.g., a request to set up a new packet connection). First, IDR determines whether to route an arriving request for a network tunnel path over the existing topology or to open a new, available optical wavelength paths.

Abstract: A packet filter for a router performs generalized packet filtering allowing range matches in two dimensions, where ranges in one dimension at least one dimension is defined as a power of two. To associate a filter rule with a received packet EP, the packet filter employs a 2-dimensional interval search and memory look-up with the filter-rule table. Values of sm of filter-rule rm=(sm,dm) in one dimension are desirably ranges that are a power of two, such as prefix ranges, which are represented by a binary value having a “length” defined as the number of bits to of the prefix. The dm may be single points, ranges defined as prefix ranges, and/or ranges defined as continuous ranges. The packet filter employs preprocessing of the filter-rules based on prefix length as a power of 2 in one dimension and decomposition of overlapping segments into non-overlapping intervals in the other dimension to form the filter-rule table.

Abstract: A filter method for designating one of a plurality of packet filter rules contained in a router for routing a packet of information through a network, each packet characterized as having parameters, the method comprising: generating one or more partitioned sets, each partitioned set associated with a different packet parameter with each partition of a set having zero or more associated filter rules; generating a vector corresponding to each of the parameters, the vector defining structure indicating one or more potential filter rules to be applied; comparing each parameter of the received packet with each partition of a corresponding partitioned set and determining one or more potential filter rules to be applied to the packet for each parameter; and determining from each of the vectors one or more identical potential filter rules associated with each vector, one of the identical filter rules capable of being applied to the received packet, with the rule to be applied being the rule of greatest priority.

Abstract: Apparatus and methods are provided for photonic contention resolution in a switch including a plurality of input modules and a plurality of output modules, wherein at least two of the plurality of input modules have cells to be transmitted to a destination output module. The photonic contention resolution device includes a plurality of coherent light sources for emitting a beam of coherent light and a plurality of tunable receivers. Each of the coherent light sources and tunable receivers are tunable by an associated input module to a plurality of distinct wavelengths. Each tunable laser preferably illuminates at least one of the plurality of tunable receivers at the particular wavelength associated with the destination output module such that one of the at least two input modules transmits its cell to the destination output module if none of the plurality of coherent light sources is illuminating its associated tunable receiver at the particular wavelength.

Abstract: A methodology and concomitant circuitry for smoothing delay sensitive traffic utilizes short term traffic forecasts and guarantees meeting a prespecified delay constraint. The pattern of incoming traffic is used to forecast estimates of future incoming data from the present and past incoming data. Corresponding to the estimate is a data rate for propagating stored data to produce a smoothed outgoing data rate, and the interval of time over which such a rate is used so as to satisfy the delay constraint. The estimation procedure is then re-invoked at the end to the time interval, which takes into account data arriving during the time interval, so as to determine the next succeeding data rate and a new time interval for propagating stored data.

Abstract: A scheduler for a packet switch capable of atomic multicasts, that is, allowing one packet at an input port to be simultaneously transmitted to multiple output ports. The scheduling algorithm sequentially polls each of the input ports to determine to which output ports it desires connection for the next transmission slot. If those output ports are available, that input port assigns itself to the slot, and subsequent input ports are blocked from those output ports. The scheduling algorithm does not poll these blocked input ports for the current slot. The scheduler can be advantageously implemented in an optical system having one optical path for indexing control and multiple optical paths corresponding to each of the output ports. Sub-schedulers are arranged serially along all the optical paths. When a sub-scheduler is notified by the indexing control path that its turn to assign has arrived, it checks all of the optical paths corresponding to the output ports to which it desires connection.