Optimal capacity placement for path restoration in STM or ATM mesh-survivable networks
TL;DR: A method for capacity optimization of path restorable networks which is applicable to both synchronous transfer mode (STM) and asynchronous transfermode (ATM) virtual path (VP)-based restoration and jointly optimizing working path routing and spare capacity placement.
Abstract: The total transmission capacity required by a transport network to satisfy demand and protect it from failures contributes significantly to its cost, especially in long-haul networks. Previously, the spare capacity of a network with a given set of working span sizes has been optimized to facilitate span restoration. Path restorable networks can, however, be even more efficient by defining the restoration problem from an end to end rerouting viewpoint. We provide a method for capacity optimization of path restorable networks which is applicable to both synchronous transfer mode (STM) and asynchronous transfer mode (ATM) virtual path (VP)-based restoration. Lower bounds on spare capacity requirements in span and path restorable networks are first compared, followed by an integer program formulation based on flow constraints which solves the spare and/or working capacity placement problem in either span or path restorable networks. The benefits of path and span restoration, and of jointly optimizing working path routing and spare capacity placement, are then analyzed.
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TL;DR: The main findings are that p-cycles do exhibit threshold hop-limiting effects at about three or four hops above those in corresponding mesh networks and that cycle limiting is a simple and effective surrogate for direct limitation on path lengths in p-cycle design problems.
14 citations
TL;DR: In this article, the authors proposed a distributed fault restoration algorithm, called the Dynamic Multiple Ring Algorithm (DMRA), for WDM mesh networks, where nodes use distributed control to search for neighboring nodes and establish the relationship between them to build numerous logical rings.
Abstract: This work describes a distributed fault restoration algorithm, called the Dynamic Multiple Ring Algorithm (DMRA), for application in WDM mesh networks. This study explores the choice of restoration paths and the assignment of fault-tolerant bandwidth when a link, node, or channel failure occurs according to the change in traffic load, number of nodes, and transmission delay including propagation and switching delays. Accordingly, the primary aim of this work is to use networking segments near faults to share the restoration load throughout a mesh network. Each node searches for restoration paths in their near environment using the proposed DMRA. Nodes use distributed control to search for neighboring nodes and to establish the relationship between them to build numerous logical rings. Nodes can also locate faults in the logical rings. These rings establish the restoration paths. The traffic load over failed links or nodes can be diverted to other paths in the networking segments. The cost of the restoration paths is computed at each node based on both the current capacity and the transmission delay. The selected restoration paths are suitable transmission routes in the network neighborhood. Hence, restoration paths can be identified and wavelength assigned quickly according to network bandwidth and traffic load. Simulation results reveal that the proposed method works extremely quickly and has a high success rate. Consequently, it is very useful for applications in real WDM networks, where the status varies from minute to minute.
14 citations
15 Dec 2003
TL;DR: The choice of restoration paths and the assignment of fault-tolerant bandwidth when a link, node, or channel failure occurs according to the change in traffic load, number of nodes, and transmission delay including propagation and switching delays is explored.
Abstract: This work proposes a distributed algorithm for fault restoration, called the dynamic multiple rings algorithm (DMRA), in a DWDM mesh network. This study explores how to choose restoration paths and distribute a fault-tolerant bandwidth when link, node and channel faults occur. Mesh network topology is becoming increasingly popular, and includes many restoration paths. Calculating the appropriate restoration paths will take a long time if the whole network is considered. Accordingly, the basic idea of this paper is trying to use networking segments near faults to share the restoration load in mesh networks. Each node is responsible for searching restoration paths around it using the proposed DMRA. Nodes use the distributed algorithm to search nearby nodes and establish the relationship between them to build many logical rings. Nodes also can locate the fault in which logical rings are, and these logical rings will establish restoration paths. The traffic load over faulty links or nodes can be diverted to other paths in the networking segments. The cost of restoration paths is computed at each node from both current capacity and transmission time. The selected restoration paths are the appropriate transmission routes in the nearby networks. Accordingly, searching restoration paths and assigning wavelength routings can be performed quickly, depending on network bandwidth and the traffic load. Furthermore, the proposed algorithm is adapted to dynamic networks, and the control messages are to be transmitted in bi-directional control channels. The proposed fault-tolerant mechanism is designed not only for a single fault, but also for multiple faults in the network. Improving the stability and load balance of the network is therefore helpful. Therefore, the method proposed herein can be adopted in a large-scale and complex network topology. The simulation environment employed in this paper is based on the architecture of NFSNet, which includes 14 nodes and 21 links. There are 10 wavelengths in each link. Each node can compute the multiple rings architecture, and some nodes will start up to broadcast to search for a multiple rings architecture in a period for the entire network topology. The traffic loads are simulated dynamically and set from 10% to 90% of entire network utilization. The blocking probability of restoration paths using DMRA is compared with that using p-cycle in various traffic loads when a fault occurs. The results show that the blocking probability using DMRA is lower than that using p-cycle. So, it is obvious that the performance of DMRA is better than that of p-cycle. Other relevant issues, such as fault restoration in GMPLS, burst switching, and load balance, are under investigation.
13 citations
TL;DR: Three approaches to cope with shared backup tree (BT) lightpath protection in multi-protocol lambda switching are proposed and compared in order to compare these approaches in terms of performance and computing effort.
Abstract: Multi-protocol lambda switching (MPλS) has recently been applied in the optical network control plane to provide fast lightpath provisioning. As an increasing amount of traffic is carried in optical transport networks (OTNs), single network failures can affect a vast amount of traffic, making lightpath protection crucial. Therefore, shared backup tree (BT) lightpath protection is a promising paradigm in MPλS networks due to its ability of fast recovery and its efficiency in consumed resources. A shared BT is used to protect a group of working lightpaths towards the same destination. From the working lightpaths in such a group, only one affected lightpath at a time can be recovered using the BT. The main problem is how to group and route the working paths (WPs) and how to route the BTs, in such a way that the capacity resources used by the WPs and the BTs are minimized. In Part One of this study (presented in this paper), we propose three approaches to cope with this problem. The first approach is a purely integer linear programming (ILP) based method. The second one is a combination of ILP and a heuristic technique. The last one is a purely heuristic approach. In this paper, these approaches are theoretically compared. In Part Two [1] of this study, several simulations are carried out in order to compare these approaches in terms of performance and computing effort. The experimental results are in line with the theoretical expectations.
13 citations
Patent•
AT&T1
TL;DR: In this article, the authors proposed a method and apparatus for increasing the capability of a network topology model having a plurality of nodes connected by existing links to maintain service continuity in the presence of faults.
Abstract: A method and apparatus for increasing the capability of a network topology model having a plurality of nodes connected by existing links to maintain service continuity in the presence of faults. The steps of the method include adding new links to the network topology model to protect against single node failures, and adjusting link weights for the network topology model to reduce at least one of a cost of network operation and an imbalance in link utilizations. Preferably, the link weights are adjusted to reduce the imbalance in link utilizations without deteriorating the cost of network operation. The link weights are preferably adjusted to reduce the cost of network operation without increasing the imbalance in link utilizations. Preferably, the link weights are adjusted to reduce the cost of network operation without increasing the imbalance in link utilizations while keeping the utilization for each link below a specific threshold. In addition, links can be added to the network topology model to reduce the cost of network operation.
13 citations
References
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Book•
16 Feb 1970
TL;DR: Interestingly, integer programming and network flows that you really wait for now is coming, it's significant to wait for the representative and beneficial books to read.
Abstract: (1970). Integer Programming and Network Flows. Journal of the Operational Research Society: Vol. 21, No. 4, pp. 500-501.
638 citations
TL;DR: Self-healing network techniques suitable for ATM networks in order to realize a high-reliablity B-ISDN are proposed and high-speed restoration technique which exploits the benefits of the VP is proposed and described.
Abstract: This paper proposes self-healing network techniques suitable for ATM networks in order to realize a high-reliablity B-ISDN. First, the characteristics of the virtual paths (VP) and their influence on failure restoration are discussed. A high-speed restoration technique which exploits the benefits of the VP is then proposed and described. The technique simplifies the message transmission processes and reduces the number of generated messages by using preassigned backup virtual paths. Next, the scheme used to design the backup VP routes and spare resource distribution for each link is proposed in order to create a network that applies the proposed restoration scheme. Next, self-reconstruction techniques of backup virtual paths are proposed for the realization of a reversionless restoration cycle. Finally, the feasibility of the distributed control operation is discussed. >
233 citations
TL;DR: A comparative study of the effectiveness of KSP versus Max Flow as an alternative rerouting criteria in the context of transport network span restoration, and the hypothesis is made that a generalized "trap" topology is responsible for all KSP-Max Flow capacity differences.
Abstract: In the development of technologies for span failure restoration, a question arises about the restoration rerouting characteristics to be specified. In theory, maximal rerouting capacity is obtained with a maximum flow (Max Flow) criterion. However, rerouting that realizes the k-successively shortest link disjoint paths (KSP) may be faster, easier, and, in distributed implementation, more robust than a distributed counterpart for Max Flow. The issue is, therefore, what the restoration capacity penalty is if KSP is used instead of Max Flow. To explore this tradeoff, the authors present a comparative study of the effectiveness of KSP versus Max Flow as an alternative rerouting criteria in the context of transport network span restoration. The comparison applies to both centrally controlled and distributed restoration systems. Study methods include exhaustive span failure experiments on a range of network models, and parametric and analytical investigations for insight into the factors resulting in KSP versus Max Flow differences. The main finding is that KSP restoration capacity is more than 99.9% of that from Max Flow in typical network models. The hypothesis is made that a generalized "trap" topology is responsible for all KSP-Max Flow capacity differences. The hypothesis is tested experimentally and used to develop analytical bounds which agree well with observed results. These findings and data are relevant to standards makers and equipment developers in specifying and engineering future restorable networks. >
199 citations
NEC1
TL;DR: In order to achieve fast restoration, a distributed control mechanism that is applicable to both line and path restoration is proposed, and the shared use of spare channels for various failure scenarios, including multiple failure cases, are allowed.
Abstract: With the advent of networking technologies intelligent network elements, such as the digital cross-connect system (DCS), will make it possible to dynamically reconfigure a network for restoration purposes. Both restoration control of DCSs and spare-channel design issues are presented, and how they work together so that a fast and economical SONET self-healing network is obtained. In order to achieve fast restoration, a distributed control mechanism that is applicable to both line and path restoration is proposed. The proposed method allows the shared use of spare channels for various failure scenarios, including multiple failure cases, so that the efficient use of spare channels can be achieved. A linear-programming-based scheme is proposed to obtain spare-channel assignment, where a network-flow technique is used. Through a simulation study, a fast and economical self-healing network is verified. >
193 citations
"Optimal capacity placement for path..." refers background or methods in this paper
...Previous work used an IP approach based on -flow -cut considerations to solve the spare capacity placement problem in a span-restorable network [4], [11], [20]....
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...Issues related to the restoration mechanisms themselves are addressed in related works [1], [2], [4], [21], [27]....
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Proceedings Article•
01 Jan 1987
180 citations