Abstract: A method of providing restoration routes for protecting traffic in a mesh network is described. The method comprises the steps of generating a set of eligible restoration routes for each span in the network, establishing a bi-criteria objective function in terms of route length and capacity cost for selecting a set of restoration routes, and selecting a set of restoration routes for each span from the eligible restoration routes in dependence upon the bi-criteria objective function. Embodiments of the invention may be useful for shortening the lengths, in terms of hops, of existing restoration routes in a mesh-restorable network and in some cases with negligible spare capacity penalty.

Abstract: A method of connecting a telecommunications network, in which the network is formed of plural nodes connected by plural spans. Each node has a nodal switching device for making connections between adjacent spans meeting at the node. Method steps A-F are followed. A) Select a set of candidate rings, each candidate ring being formed of nodes connected by spans, the candidate rings each being capable of serving a number of demands and having a ring construction cost C. B) Assess the total transport utility U of each candidate ring, wherein the total transport utility is a measure of at least the number of demands served by the respective candidate ring. C) Assess the construction cost of each candidate ring. D) Calculate a ratio formed of U/C for each candidate ring. E) Choose, from the set of candidate rings, a best set of candidate rings, wherein candidate rings in the best set of candidate rings have a higher ratio of U/C than candidate rings not in the best set.

Abstract: A simple and effective pre-processing step to reduce the complexity of solving p-cycle network design problems involving pre-selecting candidate cycles based on their topological score (TS) and a priori efficiency (AE) is disclosed. The disclosure contains a case study that examines joint optimization of working routes with placement of p-cycles.

Abstract: This disclosure introduces a significant extension to the method of p-cycles for network protection. The main advance is the generalization of the p-cycle concept to protect multi-span segments of contiguous working flow, not only spans that lie on the cycle or directly straddle the p-cycle. This effectively extends the p-cycle technique to include path protection, or protection of any flow segment along a path, as well as the original span protecting use of p-cycles. It also gives an inherent means of transit flow protection against node loss. We present a capacity optimization model for the new scheme and compare it to prior p-cycle designs and other types of efficient mesh-survivable networks. Results show that path-segment-protecting p-cycles (“flow p-cycles” for short) have capacity efficiency near that of a path-restorable network without stub release.

Abstract: A mechanism for path provisioning between an origin node (O) and a destination node (D) over BLSR networks. All ring pairs including O and D are examined and a communications path is calculated for each valid ring sequence. The calculated path is compared with the current best path until an optimal path is found. Significantly improved run-time is obtained using ring sequence reduction (RS-R) and path construction reduction (PC-R) while the quality solution set is maintained. A path provisioning tool calculates the optimal path and a Pareto curve for the BLSR network. The optimal path displays inter-ring connection configurations, the signal flows, and associated data like cost and unavailability. The Pareto curve allows various levels of assured availability to be provided while keeping the cost to a minimum.

Abstract: Whether in a SONET or a dense-WDM (DWDM) transport environment, we can expect to see a continuance of the two main survivable architectures: ring and mesh. The differing advantages of these technologies has allowed both of them to find applications, although they are usually deployed and operate quite separately. To date, the problem of optimally combining ring and mesh technologies into a single integrated transport design remains largely unstudied. This patent document presents a planning principle and related optimization theory to strategically embed rings into a mesh network, with the purpose of obtaining a lower total design cost than that of either a pure-mesh or pure-ring design. The new design approach is based on a recently developed insight into the nature of spare capacity requirements in a mesh-restorable network. So-called “forcer” analysis identifies the spans that drive the dimensioning of spare quantities in the network.

Abstract: A method for restoring traffic in a network. The network includes plural distinct nodes interconnected by plural distinct spans, each span having working links and spare links. Each node has a digital cross-connect switch for making and breaking connections between adjacent spans forming span pairs at a node. Cross-connections between spare links in adjacent spans are made such that sets of successive nodes through which the adjacent spans form span paths form closed paths. A method of finding and construction closed paths is described in which statelets are broadcast through the network. In a preferred method of implementation of the method, the statelet broadcast occurs not in response to a network failure, but across the entire network before any particular span failure and may be carried out during normal network operations as a continual re-configuration of the network.

Abstract: Ongoing growth in transport demand is served while deferring or eliminating expenditure for additional capacity by reclaiming the protection capacity and inefficiently used working capacity in existing multi-ring network. Reclamation is through re-design of the routing and restoration in the network using mesh principles within the pre-existing ring capacities. The installed working and protection capacity of existing rings is viewed as a sunk investment, an existing resource, to be “mined” and incorporated into a mesh- operated network that serves both existing and ongoing growth. Three ways of approaching the idea are given. The last is a detailed planning model for minimum cost evolution out to a given total growth multiplier (or a scenario of individual future growth multipliers on each O-D pair) that considers the costs of new mesh capacity additions, nodal costs for mesh access to existing ring working and protection capacity and selective ADM conversions and re-use decisions.

Abstract: A method of designing a telecommunications network, the method comprising the steps of A) for all working demand flows required to be routed in the telecommunications network, finding an initial topology of spans between nodes in the telecommunications network that is sufficient for routing all working demand flows, while attempting to minimize the cost of providing the spans; B) given the initial topology of spans identified in step A, finding a set of additional spans that ensures restorability of working demand flows that are required to be restored in case of failure of any span in the initial topology of spans, while attempting to minimize the cost of providing additional spans; and C) starting with the initial topology of spans and the additional spans identified in step B, finding a final topology of spans between nodes in the telecommunications network that attempts to minimize the total cost of the final topology of spans, while routing all working demand flows and ensuring restorability of working d

Abstract: A method of providing restoration routes for protecting traffic in a mesh network is described. The method comprises the steps of generating a set of eligible restoration routes for each span in the network, establishing a bi-criteria objective function in terms of route length and capacity cost for selecting a set of restoration routes, and selecting a set of restoration routes for each span from the eligible restoration routes in dependence upon the bi-criteria objective function. Embodiments of the invention may be useful for shortening the lengths, in terms of hops, of existing restoration routes in a mesh-restorable network and in some cases with negligible spare capacity penalty.

Abstract: A Method for restoring traffic in a network. The network includes plural distinct nodes interconnected by plural distinct spans, each span having working links and spare links. Each node has a digital cross-connect switch for making and breaking connections between adjacent spans forming span pairs at a node. Cross-connections between spare links in adjacent spans are made such that sets of successive nodes through which the adjacent spans form span paths form closed paths. A method of finding and construction closed paths is described in which statelets are broadcast through the network. In a preferred method of implementation of the method, the statelet broadcast occurs not in response to a network failure, but across the entire network before any particular span failure and may be carried out during normal network operations as a continual re-configuration of the network.

Abstract: A method to increase the capacity efficiency of span-restorable mesh networking on sparse facility graphs. The new approach views the network as a “meta-mesh of chain sub-networks”. This makes the prospect of WDM mesh networking more economically viable than with previous mesh-based design where the average nodal degree is low. The meta-mesh graph is a homeomorphism of the complete network in which edges are either direct spans or chains of degree-2 nodes. The main advantage is that loop-back type spare capacity is provided only for the working demands that originate or terminate in a chain, not for the entire flow that crosses chains. The latter “express” flows are entirely mesh-protected within the meta-mesh graph which is of higher average degree and hence efficiency for mesh restoration, than the network as a whole. Nodal equipment savings also arise from the grooming of express lightpaths onto the logical chain-bypass span.

Abstract: Tis invention provides a ‘capacity slice’ nodal switching device (in the ADM-like sense) that is designed for deployment under the p-cycle concept. The device's key architectural properties are access, east and west interfaces, with one spare and working port, on each of these interface sides, plus at least two straddling side interfaces. The straddling side interfaces each have equal line capacity to those of east and west interfaces, but all are usable for working capacity. In application, the plug cards in the nodal switching device are supplied to provide up to two line signal units on the straddling side of the p-cycle device, per diverse span arriving at the site. Network level deployment and configuration of the devices requires that they be arranged in p-cycles.

Abstract: A distributed method for creating telecommunications paths in a network, particularly after a span failure. The network includes plural distinct nodes interconnected by plural distinct spans, each span having working links and spare links. Each node has a digital cross-connect switch for making and breaking connections between adjacent spans forming span pairs at a node. At least one of the end nodes of a path to be created broadcasts statelets. Each intermediate node between the end nodes broadcasts incoming statelets in a manner that favours use of restoration paths that eliminate the fewest other paths. Statelets that have traversed spans with greater spare capacity, considering the number of statelets competing to be broadcast along the spans, are preferentially broadcast.

Abstract: A method for restoring traffic in a network. The network includes plural distinct nodes interconnected by plural distinct spans, each span having working links and spare links. Each node has a digital cross-connect switch for making and breaking connections between adjacent spans forming span pairs at a node. Step 1: For each of at least two possible span failures, (a) find the number of restoration routes available in case of the occurrence of each span failure, (b) determine the resources used by each restoration route, and (c) determine the amount of flow to be restored for each span failure. Step 2: find, in a computer, the amount of flow f.sup.p to be restored along each restoration route that minimizes total unrestored flow for all possible span failures identified in step 1. Step 3: form connections at each digital cross-connect switch in the network along each restoration route before occurrence of one of the possible span failures identified in step 1 to permit the amount of flow f.sup.

Abstract: Delay-tolerant calls access slack capacity in a telecommunications network under variable pricing controlled by the network so as to permit the network to pick up or stimulate background traffic loads as and when desired to gain revenue from background idle capacity.

Abstract: A method and apparatus of phase synchronizing a plurality of spatially distributed application modules having synchronizing clocks requiring synchronization, each application module being connected, at a predetermined site nearest the module, to an outgoing path and, at a corresponding site nearest the module, a return path of a pulse reference path, the method comprising the steps of injecting reference pulses at a predetermined frequency into an injection site of the reference path such that the pulses travel along the outgoing path to a remote site and return to the injection site along the return path; determining, for each application module, the time interval for each pulse to travel from the predetermined site to the corresponding site associated with the application module; monitoring, for each application module, the elapsed time interval for each pulse to travel between the predetermined and corresponding sites associated with the application module; producing, for each application module, a local p

Abstract: A method for determining the highest, common bi-directional transmission rate between two stations of an ISDN communications link includes the steps of a) selecting a candidate transmission rate from a range of candidate transmission rates, b) transmitting a test signal at the candidate transmission rate through an attenuator along the link from one of the stations to the other of the stations for a first predetermined time interval, c) determining whether a return signal transmitted by the other station over the link and at the candidate transmission rate has been correctly received at the one station, d) repeating steps a), b) and c) until predetermined criteria have been satisfied; and e) storing the highest candidate transmission rate for which a return signal at that rate was correctly received within the first time interval; and f) removing the attenuator for final verification of operation.

Abstract: A method of modulating a DS3 signal for addition thereto of an auxiliary, transparent signalling channel, the DS3 signal having framing bits which provide a predetermined pattern for which frame-finding circuits hunt to demultiplex the payload of the DS3 signal. The method comprises cyclically forcing an framing-bit error onto every D-spaced framing-bit of the DS3 signal during an initial ON period of an ON-oFF modulation cycle, the ON period and the modulation cycle having lengths such that no more than two verification attempts are required to complete reframing of the signal in the presence of the framing-bit modulation, and wherein the Modulation Spacing, D, is selected so as to provide a low probability of coincidence between the framing-bit Modulation Spacing and a verification window following a secondary reframing hunt.

Abstract: A method and apparatus of restoring communications between a pair of nodes in a network having an arbitrary number of nodes and an arbitrary number of spans interconnecting the nodes, each span having working circuits between nodes designated for transmitting actual communications traffic and spare circuits capable of, but not designated for, transmitting actual communications traffic, the method comprising the steps of (a) establishing one or more independent communication paths between the pair of nodes through a series of spare circuits of spans interconnecting the pair of nodes and other interconnected nodes in the network; and (b) redirecting communications traffic intended for one or more failed spans interconnecting the pair of nodes through one or more of the paths.