IP Fast Reroute in Networks with Shared Risk Links

Abstract. IP fast reroute is a mechanism that is used to reroute packets around a failed link as soon as the link fails. Most of the IP fast reroute mechanisms, that have been proposed so far, focus on single or dual link failures but can not handle Shared Risk Link Group (SRLG) failures when several links fail at the same time because of some common underlying component failure. Furthermore, most of current work is based on the assumption that each node in the network has access to some global topology information of the network. In this paper, we present the first IP fast reroute mechanism for SRLG failures that is not based on the assumption that the nodes in the network have global topology information of the network. In our mechanism, nodes in the network use "relay bits" to identify themselves as "relay nodes" for a reroute link in a fully distributed mannner. Through simulation, we show that our mechanism succeeds in rerouting around SRLG failures alomst 100% of the time, with average length of a reroute path about 1.5 times the re-converged shortest path

Exploring the Limits of Static Failover Routing

We present and study the Static-Routing-Resiliency problem, motivated by routing on the Internet: Given a graph $G$, a unique destination vertex $d$, and an integer constant $c>0$, does there exist a static and destination-based routing scheme such that the correct delivery of packets from any source $s$ to the destination $d$ is guaranteed so long as (1) no more than $c$ edges fail and (2) there exists a physical path from $s$ to $d$? We embark upon a systematic exploration of this fundamental question in a variety of models (deterministic routing, randomized routing, with packet-duplication, with packet-header-rewriting) and present both positive and negative results that relate the edge-connectivity of a graph, i.e., the minimum number of edges whose deletion partitions $G$, to its resiliency.Comment: 30 page

Efficient Algorithms to Enhance Recovery Schema in Link State Protocols

With the increasing demands for real-time applications traffic in net- works such as video and voice a high convergence time for the existing routing protocols when failure occurred is required. These applications can be very sensitive to packet loss when link/node goes down. In this paper, we propose two algorithms schemas for the link state protocol to reroute the traffic in two states; first, pre-calculated an alternative and disjoint path with the primary one from the source to the destination by re-routing traffic through it, regardless of the locations of failure and the number of failed links. Second, rerouting the traffic via an alternative path from a node whose local link is down without the need to wait until the source node knows about the failure. This is achieved by creating a new backup routing table based on the original routing table which is computed by the dijkstra algorithm. The goal of these algorithms is to reduce loss of packets, end-to-end delay time, improve throughput and avoiding local loop when nodes re-converge the topology in case of failure.Comment: 15 page

Survivability issues in WDM optical networks

WDM optical networks make it possible for the bandwidth of transport networks to reach a level on which any failures would cause tremendous data loss and affect a lot of users. Thus, survivability issues of WDM optical networks have attracted a lot of research work. Within the scope of this dissertation, two categories of problems are studied, one is survivable mapping from IP topology to WDM topology, the other is p-cycle protection schemes in WDM networks.;Survivable mapping problem can be described as routing IP links on the WDM topology such that the IP topology stays connected under any single link failure in the WDM topology. This problem has been proved to be NP-complete [1]. At first, this dissertation provides a heuristic algorithm to compute approximated solutions for input IP/WDM topologies as an approach to ease the hardness of it. Then, it examines the problem with a different view, to augment the IP topology so that a survivable mapping can be easily computed. This new perspective leads to an extended survivable mapping problem that is originally proposed and analyzed in this dissertation. In addition, this dissertation also presents some interesting open problems for the survivable mapping problem as future work.;Various protection schemes in WDM networks have been explored. This dissertation focuses on methods based on the p-cycle technology. p-Cycle protection inherits the merit of fast restoration from the link-based protection technology while yielding higher efficiency on spare capacity usage [2]. In this dissertation, we first propose an efficient heuristic algorithm that generates a small subset of candidate cycles that guarantee 100% restorability and help to achieve an efficient design. Then, we adapt p-cycle design to accommodate the protection of the failure of a shared risk link group (SRLG). At last, we discuss the problem of establishing survivable connections for dynamic traffic demands using flow p-cycle

Comparison of New Solutions in IP Fast Reroute

Currently, network requirements are placed on the efficiency and size of the networks. These conditions can be ensured by modern converged networks that integrate the functions of both data and telecommunication networks. Line or router failures have always been a part of transmission networks, which is no different from converged networks. As a result of outages, which can take from ms to tens of seconds, packets are lost. These outages cause degraded transmission quality, which is undesirable when transmitting real-time multimedia services (Voice over IP, video). To solve the mentioned problems, the IETF organization has developed IP Fast Reroute mechanisms to minimise the time to restore the connection after a line or node failure and, consequently, less packet loss. The article reviews and compares the latest IP Fast Reroute mechanisms deployed in the last three years. First, we have Optimistic Fast Rerouting, which calculates optimistic and fallback scenarios. The second is Post-processing Fast Reroute, which decomposes the network according to metrics such as load and route length. Third, Local Fast Reroute focused on low congestion and random access

Demand Engineering: IP Network Optimisation Through Intelligent Demand Placement

Traffic engineering has been used in IP and MPLS networks for a number of years as a tool for making more efficient use of capacity by explicitly routing traffic demands where there is available network capacity that would otherwise be unused. Deployment of traffic engineering imposes an additional layer of complexity to network design and operations, however, which has constrained its adoption for capacity optimisation. The rise of Software Defined Networks has renewed interest in the use of traffic engineering approaches leveraging centralised network controllers for capacity optimisation. We argue that future networks can realise the network optimisation benefits of traffic engineering without incurring additional network complexity through closer coupling between the network and the applications and services using the network. This can be achieved through leveraging a network- and traffic-aware controller to directly influence where applications and services site or locate service instances, i.e. which implicitly impacts the paths that the applications or services traffic demands take through the network. We call this technique Demand Engineering. Demand Engineering has the additional benefit of providing an admission control capability, i.e. which can provide an assurance that network SLAs can be met. In this paper we describe the concept of Demand Engineering, give examples of its use and present simulation results indicating its potential benefits. We also compare demand engineering to traffic engineering

An efficient pre-computed backup path on the IGP network communication

Currently, data communication during heavy traffic transmission on the network suffers from node failures. A failure in the network is required to be restored by the routing protocols in the networks. Traditional routing protocols schemes normally compute a routing table which contains all paths between all nodes on the network. Hence, the data packets will be passed via the single shortest path which is the best path between each source and destination. In this paper, a pre-computed alternate path is introduced to assist the congested networks to continue passing the data packets from its source to the final destination once failure occurs. The proposed alternative routing table (ART) algorithm aims to re-route the traffic through a backup route when the primary path has failed. We have evaluated the performance of the proposed scheme with OSPF routing protocol through NS2 simulator. The results show that packet losses, rerouting and end to end delay times of the proposed methods are substantially improved

Analysis, Review and Optimization of SONET/SDH Technology for today and future aspects

Network layers are analyzed for their design and issues of researches, while dense wavelength division multiplexing equipment has been deployed in networks of major telecommunications carriers for a long time, the efficiency of networking and relation with network control and management have not caught up to those of digital cross-connect systems and packet-switched counterparts in higher layer networks