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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Book•
01 Jan 2004TL;DR: Throughout, the authors focus on the traffic demands encountered in the real world of network design, and their generic approach allows problem formulations and solutions to be applied across the board to virtually any type of backbone communication or computer network.
Abstract: In network design, the gap between theory and practice is woefully broad. This book narrows it, comprehensively and critically examining current network design models and methods. You will learn where mathematical modeling and algorithmic optimization have been under-utilized. At the opposite extreme, you will learn where they tend to fail to contribute to the twin goals of network efficiency and cost-savings. Most of all, you will learn precisely how to tailor theoretical models to make them as useful as possible in practice. Throughout, the authors focus on the traffic demands encountered in the real world of network design. Their generic approach, however, allows problem formulations and solutions to be applied across the board to virtually any type of backbone communication or computer network. For beginners, this book is an excellent introduction. For seasoned professionals, it provides immediate solutions and a strong foundation for further advances in the use of mathematical modeling for network design. (Less)
1,093 citations
TL;DR: Numerical results comparing several SCA algorithms show that SSR has the best trade-off between solution optimality and computation speed.
Abstract: The design of survivable mesh based communication networks has received considerable attention in recent years. One task is to route backup paths and allocate spare capacity in the network to guarantee seamless communications services survivable to a set of failure scenarios. This is a complex multi-constraint optimization problem, called the spare capacity allocation (SCA) problem. This paper unravels the SCA problem structure using a matrix-based model, and develops a fast and efficient approximation algorithm, termed successive survivable routing (SSR). First, per-flow spare capacity sharing is captured by a spare provision matrix (SPM) method. The SPM matrix has a dimension the number of failure scenarios by the number of links. It is used by each demand to route the backup path and share spare capacity with other backup paths. Next, based on a special link metric calculated from SPM, SSR iteratively routes/updates backup paths in order to minimize the cost of total spare capacity. A backup path can be further updated as long as it is not carrying any traffic. Furthermore, the SPM method and SSR algorithm are generalized from protecting all single link failures to any arbitrary link failures such as those generated by Shared Risk Link Groups or all single node failures. Numerical results comparing several SCA algorithms show that SSR has the best trade-off between solution optimality and computation speed.
237 citations
Cites methods or result from "Optimal capacity placement for path..."
...This technique is also used to input candidate paths into InP formulation when Branch and Bound (BB) is employed for searching the near optimal solution [ 35 ], [37]....
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...Compared with the path-flow formulations in [ 35 ], [42], this arc-flow model needs additional constraints to find feasible backup paths, but pre-calculated backup path sets are not necessary....
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TL;DR: The factors that affect the complexity of optical protection schemes, such as supporting mesh instead of ring protection, handling low-priority traffic, and dealing with multiple types of failures are discussed.
Abstract: This paper looks at several aspects of optical layer protection techniques from an implementation perspective. We discuss the factors that affect the complexity of optical protection schemes, such as supporting mesh instead of ring protection, handling low-priority traffic, and dealing with multiple types of failures. The paper also looks at how the client layer interacts with the optical layer with respect to protection, in terms of how client connections are mapped into the optical layer, and how protection schemes in both layers can work together in efficient ways. Finally, we describe several interesting optical protection implementations, focusing on the ones that are different from conventional SONET-like implementations.
194 citations
Cites background from "Optimal capacity placement for path..."
..., [16], [26], [13]) to make use of the promised bandwidth efficiency of mesh protection....
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TL;DR: This study addresses the routing and wavelength-assignment problem in a network with path protection under duct-layer constraints in a wavelength-division multiplexing (WDM) network in which failures occur due to fiber cuts.
Abstract: This study investigates the problem of fault management in a wavelength-division multiplexing (WDM)-based optical mesh network in which failures occur due to fiber cuts. In reality, bundles of fibers often get cut at the same time due to construction or destructive natural events, such as earthquakes. Fibers laid down in the same duct have a significant probability to fail at the same time. When path protection is employed, we require the primary path and the backup path to be duct-disjoint, so that the network is survivable under single-duct failures. Moreover, if two primary paths go through any common duct, their backup paths cannot share wavelengths on common links. This study addresses the routing and wavelength-assignment problem in a network with path protection under duct-layer constraints. Off-line algorithms for static traffic is developed to combat single-duct failures. The objective is to minimize total number of wavelengths used on all the links in the network. Both integer linear programs and a heuristic algorithm are presented and their performance is compared through numerical examples.
189 citations
22 Apr 2001
TL;DR: Numerical results comparing several SCA algorithms show that SSR has the best trade-off between solution optimality and computation speed.
Abstract: Spare capacity allocation (SCA) is an important part of a fault tolerant network design. In the spare capacity allocation problem one seeks to determine where to place spare capacity in the network and how much spare capacity must be allocated to guarantee seamless communications services survivable to a set of failure scenarios (e.g., any single link failure). Formulated as a multi-commodity flow integer programming problem, SCA is known to be NP-hard. We provide a two-pronged attack to approximate the optimal SCA solution: unravel the SCA structure and find an effective algorithm. First, a literature review on the SCA problem and its algorithms is provided. Second, a integer programming model for SCA is provided. Third, a simulated annealing algorithm using the above INP model is introduced. Next, the structure of SCA is modeled by a matrix method. The per-flow based backup path information are aggregated into a square matrix, called the spare provision matrix (SPM). The size of the SPM is the number of links. Using the SPM as the state information, a new adaptive algorithm is then developed to approximate the optimal SCA solution termed successive survivable routing (SSR). SSR routes link-disjoint backup paths for each traffic flow one at a time. Each flow keeps updating its backup path according to the current network state as long as the backup path is not carrying any traffic. In this way, SSR can be implemented by shortest path algorithms using advertised state information with complexity of O( Link/sup 2/). The analysis also shows that SSR is using a necessary condition of the optimal solution. The numerical results show that SSR has near optimal spare capacity allocation with substantial advantages in computation speed.
177 citations
Cites methods from "Optimal capacity placement for path..."
...Multi-commodity flow (MCF) models have been widely used to formulate spare capacity allocation problems in different networks like SONET/SDH [19], [20], [21], [6], [22], ATM [6], [7], WDM [8], [9], and IP/MPLS [23]....
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...This technique can also be extended to input InP formulation when Branch and Bound (BB) is employed for searching the optimal solution [20], [6]....
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References
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14 Jun 1992
TL;DR: Algorithms and tools which are useful both to support the activity of network planners and to build an automatic network protection system are presented.
Abstract: The protection of transmission networks is discussed. Algorithms and tools which are useful both to support the activity of network planners and to build an automatic network protection system are presented. A definition of general and constrained routing and protection problems in a transmission network is given. Protection planning tools, their functions,and implementation are discussed. An algorithm for multiconstrained routing and protection problems is introduced. The concept of the automatic network protection system is given, and its main features are described. The results of a protection study carried out using the described algorithms are presented. >
14 citations
DOI•
01 Dec 1997TL;DR: In this article, the authors propose an optimized distributed real-time path restoration mechanism, named OPRA, which synthesizes link-disjoint loop-free pathsets that are very close to the multicommodity, max-flow ideal by autonomous, database-free, self-organizing interaction between nodes.
Abstract: Intense competition between transport network service providers and the widespread deployment of vulnerable high-capacity fiber optic transport facilities has created the need for capacity-efficient transport networks with short restoration times. Ensuring service continuity affordably and quickly is called the restoration problem in modern tellecommunications practice. Solving the restoration problem not only requires restoring a failure quickly, but determining an economic capacity placement which permits full restoration. This thesis solves the restoration problem in path restorable mesh networks by formulating a capacity design methodology, and an optimized distributed real time path restoration mechanism, named OPRA.
One of the main contributions of this thesis is OPRA. OPRA synthesizes link-disjoint loop-free pathsets that are very close to the multicommodity, max-flow ideal by autonomous, database-free, self-organizing interaction between nodes. The results presented in this thesis show that OPRA will in practice very likely restore a failure in a tightly spared network in less than two seconds, regardless of a network's size and topology, the distribution of alarms in time, and the number and location of connected demand pairs affected by a failure.
The second main contribution of this thesis is the capacity design methodology which uses integer programming. The integer program formulated in this thesis uses flow constraints based on a suitable set of predefined routes over which pathsets are implemented to optimize the spare and/or working capacity of a path restorable network. The results presented in this thesis show mesh restorable networks using path restoration are the most capacity efficient, reducing the total capacity of the corresponding span restorable network design by up to 19%.
Together these advances make feasible path restorable transport networks which restore failures within two seconds and require less spare capacity than existing transport networks. In the envisaged network, capacity would be minimized using the integer program, and failures would be restored in real time in an entirely autonomous distributed manner using OPRA.
7 citations
"Optimal capacity placement for path..." refers background or methods in this paper
...This routing information may be used directly in the case of a centralized restoration control strategy or used as the ideal reference solution in assessing the efficiency of a distributed real-time protocol for path restoration, as in recent studies of a real-time path restoration protocol [21]....
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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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TL;DR: In this paper, an integer program formulation permitting controlled exploitation of this intrinsic difference between ATM and STM transport is presented. But the authors do not consider the impact of restoring VP restoration on the overall capacity of the network.
Abstract: Work on capacity design for VP restoration in ATM has to date either been heuristic in nature or has treated the capacity design problem in a 1 for 1 VP replacement manner that is essentially the same as for STM path restorable networks. However, the inherently statistical nature of the traffic in ATM should allow formulation of a backup VP restoration capacity design that permits a controlled maximum of convergent flow overloads on spans during restoration. Results show that significant capacity savings can be obtained relative to STM if ATM restoration is allowed even modest restoration overload factors. We give an integer program formulation permitting controlled exploitation of this intrinsic difference between ATM and STM transport and present results showing the significant capacity benefits motivating this approach.
5 citations
"Optimal capacity placement for path..." refers methods in this paper
...Results for the ATM case are presented and analyzed separately [24]....
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