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Recovery from Link Failures in Networks with Arbitrary Topology via Diversity Coding

Link failures in wide area networks are common. To recover from such failures, a number of methods such as SONET rings, protection cycles, and source rerouting have been investigated. Two important considerations in such approaches are the recovery time and the needed spare capacity to complete the recovery. Usually, these techniques attempt to achieve a recovery time less than 50 ms. In this paper we introduce an approach that provides link failure recovery in a hitless manner, or without any appreciable delay. This is achieved by means of a method called diversity coding. We present an algorithm for the design of an overlay network to achieve recovery from single link failures in arbitrary networks via diversity coding. This algorithm is designed to minimize spare capacity for recovery. We compare the recovery time and spare capacity performance of this algorithm against conventional techniques in terms of recovery time, spare capacity, and a joint metric called Quality of Recovery (QoR). QoR incorporates both the spare capacity percentages and worst case recovery times. Based on these results, we conclude that the proposed technique provides much shorter recovery times while achieving similar extra capacity, or better QoR performance overall.

Hitless recovery from link failures in networks with arbitrary topology

Link failures in wide area networks are common. To recover from such failures, a number of methods such as SONET rings, protection cycles, and source rerouting have been investigated. Two important considerations in such approaches are the recovery time and the needed spare capacity to complete the recovery. Usually, these techniques attempt to achieve a recovery time less than 50 ms. In this paper we introduce an approach that provides link failure recovery in a hitless manner, or without any appreciable delay. This is achieved by means of a method previously introduced, named diversity coding. We present an algorithm for the design of an overlay network to achieve hitless recovery from single link failures in arbitrary networks via diversity coding. This algorithm is designed to minimize spare capacity for recovery. We compare the spare capacity performance of this algorithm against conventional techniques from the literature via simulations. Based on these results, we conclude that the spare capacity requirements of the proposed technique are favorably comparable to existing techniques, while its recovery time performance is much better, since it can provide hitless recovery.

Coded path protection: Efficient conversion of sharing to coding

Link failures in wide area networks are common and cause significant data losses. Mesh-based protection schemes offer high capacity efficiency but they are slow and require complex signaling. Additionally, real-time reconfigurations of cross-connects threaten their transmission integrity. On the other hand, there are other schemes that are proactive. Proactivity results in higher restoration speed, lower signaling complexity, and higher transmission integrity. This paper introduces a coding-based proactive protection scheme, named Coded Path Protection (CPP). In CPP, a backup stream of the primary data is encoded with other data streams, resulting in capacity savings. In addition to a systematic approach of building valid coding structures, this paper presents an optimal and simple capacity placement and coding group formation algorithm. The algorithm converts the sharing structure of any solution of a Shared Path Protection (SPP) technique into a coding structure with minimum extra capacity. We conducted quantitative and qualitative comparisons of our technique with SPP and Shared Link Protection (SLP). Simulation results confirm that the CPP is significantly faster than both the SPP and the SLP. It is clearly more capacity efficient than the SLP while it incurs marginal extra capacity beyond that of the SPP.

Optimal algorithms for near-hitless network restoration via diversity coding

Coding-based restoration techniques have proactive restoration which results in time savings over other state-of-the-art restoration techniques. Diversity coding is a coding-based recovery technique which offers near-hitless restoration with a competitive spare capacity requirement with respect to other techniques. In this paper, we show that diversity coding can achieve sub-ms restoration time. In addition, we develop two optimal algorithms for pre-provisioning of the static traffic and one for the dynamic provisioning of the traffic on-demand. There is one algorithm for systematic and one for non-systematic diversity coding in pre-provisioning. An MIP formulation and an ILP formulation are developed for systematic and non-systematic cases, respectively. The MIP formulation of the systematic diversity coding requires much fewer integer variables and constraints than similar optimal coding-based formulations. In dynamic provisioning, an ILP-based algorithm covers both of the systematic and non-systematic diversity coding. In all scenarios, diversity coding results in smaller restoration time, higher transmission integrity, and much reduced signaling complexity than the existing techniques in the literature. Simulation results indicate that diversity coding has significantly higher restoration speed than Shared Path Protection (SPP) and p-cycle techniques from the literature as well as Synchronous Optical Network (SONET) rings, which are commonly deployed by service providers today. In terms of capacity efficiency, it outperforms SONET rings and 1+1 APS, whereas it may require more extra capacity than the p-cycle technique and SPP. Diversity coding offers a preferable tradeoff which offers two orders of magnitude increase in restoration speed at the expense of less than 26% extra spare capacity.

Extended diversity coding: Coding protection and primary paths for network restoration

The technique of diversity coding offers fast recovery against failures in networks while keeping spare capacity comparable to the alternative state-of-the art network restoration techniques. It provides near-hitless recovery when coding is performed on connections with the same destination node. When the coding structure is extended to cover the primary paths, diversity coding can achieve higher capacity efficiency than its conventional version and other restoration techniques. In this paper, we develop a systematic approach to implement the diversity coding structures for pre-provisioning with coding of the protection and primary paths. In addition, we present an algorithm to map these coding structures into arbitrary topologies. We present simulation results that show capacity efficiency of diversity coding.

Network coding-based link failure recovery over large arbitrary networks

Network coding-based link failure recovery techniques provide near-hitless recovery and offer high capacity efficiency. Diversity coding is the first technique to incorporate coding in this field and is easy to implement over small arbitrary networks. However, its capacity efficiency is restricted by its systematic coding and high design complexity even though it has lower complexity than the other coding-based recovery techniques. Alternative techniques mitigate some of these limitations, but they are difficult to implement over arbitrary networks. In this paper, we propose a novel non-systematic coding technique and a simple design algorithm to implement the diversity coding-based (or network coding-based) recovery over arbitrary networks. The design framework consists of two parts. An ILP formulation for each part is developed. The simulation results suggest that both the novel coding structure and the novel design algorithm lead to higher capacity efficiency for near-hitless recovery. The new design algorithm is able to achieve optimal results in large arbitrary networks.

Link failure recovery in large arbitrary networks via network coding

Network coding-based link failure recovery techniques provide near-hitless recovery and offer high capacity efficiency. In this paper, we propose a simple column generation-based design algorithm and a novel advanced diversity (network) coding technique to achieve near-hitless recovery in large networks. The main problem is solved with Linear Programming (LP) and Integer Linear Programming (ILP), whereas the subproblem can be solved with different methods. Simulation results suggest that both the novel coding structure and the novel design algorithm lead to higher capacity efficiency for near-hitless recovery. The novel design algorithm simplifies the capacity placement problem which enables implementing diversity coding-based techniques in large networks with arbitrary topology.

New diversity coding design algorithms for link failure recovery in communication networks

Diversity coding is a form of network coding for link failure recovery in communication networks. Since it employs coding, there is no feedback signaling, and that feature makes it very fast. Previously, we have employed this basic technique and linear programming to come up with fast link failure recovery systems that also have small extra capacity. One approach, Diversity Coding Tree, employs mixed integer programming and results in very fast restoration. Another approach is called Coded Path Protection, and employs integer linear programming and has the advantage of small extra capacity. This latter technique is based on former work that considers a communication network as consisting of bidirectional links. However, employing coding on bidirectional links results in larger restoration times than the former technique. In this paper, we develop an improved version of our former techniques. This new technique employs a mixed integer linear programming formulation and results in restoration times as fast as Diversity Coding Tree with reduced extra capacity.

Link Failure Recovery Over Large Arbitrary Networks: The Case of Coding

Network coding-based link failure recovery techniques provide near-hitless recovery and offer high capacity efficiency. Diversity coding is the first technique to incorporate coding in this field and is easy to implement over small networks. However, the capacity efficiency of this implementation is restricted by its systematic coding and high design complexity despite having lower complexity than the other coding-based recovery techniques. In this paper, we propose a simple column generation-based design algorithm and a novel advanced diversity coding technique to achieve near-hitless recovery over large networks. The traffic matrix, which consists of unicast connection demands, is decomposed into traffic vectors for each destination node. Further, the connection demands in each traffic vector are partitioned into coding groups. The design framework consists of two parts: a main problem and a subproblem. The main problem is solved with Linear Programming (LP) and Integer Linear Programming (ILP), whereas the subproblem can be solved with different methods. Simulation results suggest that the novel design algorithm simplifies the capacity placement problem, which enables implementing diversity coding-based recovery including the novel coding structure on large networks with arbitrary topology. It achieves near-hitless recovery with an almost optimal capacity efficiency for any single destination-based recovery.