Optimizing IGP Link Costs for Improving IP-level Resilience

Recently, major vendors have introduced new router platforms to the market that support fast IP-level failure pro- tection out of the box. The implementations are based on the IP Fast ReRoute–Loop Free Alternates (LFA) standard. LFA is simple, unobtrusive, and easily deployable. This simplicity, however, comes at a severe price, in that LFA usually cannot protect all possible failure scenarios. In this paper, we give new graph theoretical tools for analyzing LFA failure case coverage and we seek ways for improvement. In particular, we investigate how to optimize IGP link costs to maximize the number of protected failure scenarios, we show that this problem is NP- complete even in a very restricted formulation, and we give exact and approximate algorithms to solve it. Our simulation studies show that a deliberate selection of IGP costs can bring many networks close to complete LFA-based protection

Fast emergency paths schema to overcome transient link failures in ospf routing

A reliable network infrastructure must be able to sustain traffic flows, even when a failure occurs and changes the network topology. During the occurrence of a failure, routing protocols, like OSPF, take from hundreds of milliseconds to various seconds in order to converge. During this convergence period, packets might traverse a longer path or even a loop. An even worse transient behaviour is that packets are dropped even though destinations are reachable. In this context, this paper describes a proactive fast rerouting approach, named Fast Emergency Paths Schema (FEP-S), to overcome problems originating from transient link failures in OSPF routing. Extensive experiments were done using several network topologies with different dimensionality degrees. Results show that the recovery paths, obtained by FEPS, are shorter than those from other rerouting approaches and can improve the network reliability by reducing the packet loss rate during the routing protocols convergence caused by a failure.Comment: 18 page

High Availability in the Future Internet

With the evolution of the Internet, a huge number of real- time applications, like Voice over IP, has started to use IP as primary transmission medium. These services require high availability, which is not amongst the main features of today’s heterogeneous Internet where fail- ures occur frequently. Unfortunately, the primary fast resilience scheme implemented in IP routers, Loop-Free Alternates (LFA), usually does not provide full protection against failures. Consequently, there has been a growing interest in LFA-based network optimization methods, aimed at tuning some aspect of the underlying IP topology to maximize the ratio of failure cases covered by LFA. The main goal of this chapter is to give a comprehensive overview of LFA and survey the related LFA network op- timization methods, pointing out that these optimization tools can turn LFA into an easy-to-deploy yet highly effective IP fast resilience scheme

Smart Sensor Technologies for IoT

The recent development in wireless networks and devices has led to novel services that will utilize wireless communication on a new level. Much effort and resources have been dedicated to establishing new communication networks that will support machine-to-machine communication and the Internet of Things (IoT). In these systems, various smart and sensory devices are deployed and connected, enabling large amounts of data to be streamed. Smart services represent new trends in mobile services, i.e., a completely new spectrum of context-aware, personalized, and intelligent services and applications. A variety of existing services utilize information about the position of the user or mobile device. The position of mobile devices is often achieved using the Global Navigation Satellite System (GNSS) chips that are integrated into all modern mobile devices (smartphones). However, GNSS is not always a reliable source of position estimates due to multipath propagation and signal blockage. Moreover, integrating GNSS chips into all devices might have a negative impact on the battery life of future IoT applications. Therefore, alternative solutions to position estimation should be investigated and implemented in IoT applications. This Special Issue, “Smart Sensor Technologies for IoT” aims to report on some of the recent research efforts on this increasingly important topic. The twelve accepted papers in this issue cover various aspects of Smart Sensor Technologies for IoT

Efficient Routing Protection Algorithm Based on Optimized Network Topology

Network failures are unavoidable and occur frequently. When the network fails, intra-domain routing protocols deploying on the Internet need to undergo a long convergence process. During this period, a large number of messages are discarded, which results in a decline in the user experience and severely affects the quality of service of Internet Service Providers (ISP). Therefore, improving the availability of intra-domain routing is a trending research question to be solved. Industry usually employs routing protection algorithms to improve intra-domain routing availability. However, existing routing protection schemes compute as many backup paths as possible to reduce message loss due to network failures, which increases the cost of the network and impedes the methods deployed in practice. To address the issues, this study proposes an efficient routing protection algorithm based on optimized network topology (ERPBONT). ERPBONT adopts the optimized network topology to calculate a backup path with the minimum path coincidence degree with the shortest path for all source purposes. Firstly, the backup path with the minimum path coincidence with the shortest path is described as an integer programming problem. Then the simulated annealing algorithm ERPBONT is used to find the optimal solution. Finally, the algorithm is tested on the simulated topology and the real topology. The experimental results show that ERPBONT effectively reduces the path coincidence between the shortest path and the backup path, and significantly improves the routing availability

Scalability and Resilience Analysis of Software-Defined Networking

Software-defined Networking (SDN) ist eine moderne Architektur für Kommunikationsnetze, welche entwickelt wurde, um die Einführung von neuen Diensten und Funktionen in Netzwerke zu erleichtern. Durch eine Trennung der Weiterleitungs- und Kontrollfunktionen sind nur wenige Kontrollelemente mit Software-Updates zu versehen, um Veränderungen am Netz vornehmen zu können. Allerdings wirft die Netzstrukturierung von SDN neue Fragen bezüglich Skalierbarkeit und Ausfallsicherheit auf, welche in dezentralen Netzstrukturen nicht auftreten. In dieser Arbeit befassen wir uns mit Fragestellungen zu Skalierbarkeit und Ausfallsicherheit in Bezug auf Unicast- und Multicast-Verkehr in SDN-basierten Netzen. Wir führen eine Komprimierungstechnik für Routingtabellen ein, welche die Skalierungsproblematik aktueller SDN Weiterleitungsgeräte verbessern soll und ermitteln ihre Effizienz in einer Leistungsbewertung. Außerdem diskutieren wir unterschiedliche Methoden, um die Ausfallsicherheit in SDN zu verbessern. Wir analysieren sie auf öffentlich zugänglichen Netzwerken und benennen Vor- und Nachteile der Ansätze. Abschließend schlagen wir eine skalierbare und ausfallsichere Architektur für Multicast-basiertes SDN vor. Wir untersuchen ihre Effizienz in einer Leistungsbewertung und zeigen ihre Umsetzbarkeit mithilfe eines Prototypen.Software-Defined Networking (SDN) is a novel architecture for communication networks that has been developed to ease the introduction of new network services and functions. It leverages the separation of the data plane and the control plane to allow network services to be deployed solely in software. Although SDN provides great flexibility, the applicability of SDN in communication networks raises several questions with regard to scalability and resilience against network failures. These concerns are not prevalent in current decentralized network architectures. In this thesis, we address scalability and resilience issues with regard to unicast and multicast traffic for SDN-based networks. We propose a new compression method for inter-domain routing tables to address hardware limitations of current SDN switches and analyze its effectiveness. We propose various resilience methods for SDN and identify their key performance indicators in the context of carrier-grade and datacenter networks. We discuss the advantages and disadvantages of these proposals and their appropriate use cases. Finally, we propose a scalable and resilient software-defined multicast architecture. We study the effectiveness of our approach and show its feasibility using a prototype implementation

Recursive Loop-Free Alternates for full protection against transient link failures

In this paper, we propose a routing technique, “recursive Loop-Free Alternates (rLFAs)”, to alleviate packet loss due to transient link failures. The technique consists of a backup path calculation with corresponding re-routing scheme based on the Loop-Free Condition (LFC) as defined in the basic specification for IP Fast Re-Route (IPFRR). Under this routing strategy, nodes calculate backup paths by modifying the weights of links in the primary shortest path tree. If a failure occurs, the detecting node determines the number of recursions, which indicates the number of times packets must be forwarded along the alternate next hops to bypass the failed link. This technique guarantees full repair coverage for single link failures. We evaluate the performance of our proposed technique through simulations and show that the incurred overheads, the stretch of its pre-computed alternate paths, and the failure-state Maximum Link Utilisation (MLU) are minimal

Carrier grade resilience in geographically distributed software defined networks

The Internet is a fundamental infrastructure in modern life, supporting many different communication services. One of the most critical properties of the Internet is its ability to recover from failures, such as link or equipment failure. The goal of network resilience heavily influenced the design of the Internet, leading to the use of distributed routing protocols. While distributed algorithms largely solve the issue of network resilience, other concerns remain. A significant concern is network management, as it is a complex and error-prone process. In addition, network control logic is tightly integrated into the forwarding devices, making it difficult to upgrade the logic to introduce new features. Finally, the lack of a common control platform requires new network functions to provide their own solutions to common, but challenging, issues related to operating in a distributed environment. A new network architecture, software-defined networking (SDN), aims to alleviate many of these network challenges by introducing useful abstractions into the control plane. In an SDN architecture, control functions are implemented as network applications, and run in a logically centralized network operating system (NOS). The NOS provides the applications with abstractions for common functions, such as network discovery, installation of forwarding behaviour, and state distribution. Network management can be handled programmatically instead of manually, and new features can be introduced by simply updating or adding a control application in the NOS. Given proper design, an SDN architecture could improve the performance of reactive approaches to restoring traffic after a network failure. However, it has been shown in this dissertation that a reactive approach to traffic restoration will not meet the requirements of carrier grade networks, which require that traffic is redirected onto a back-up route less than 50 ms after the failure is detected. To achieve 50 ms recovery, a proactive approach must be used, where back-up rules are calculated and installed before a failure occurs. Several different protocols implement this proactive approach in traditional networks, and some work has also been done in the SDN space. However, current SDN solutions for fast recovery are not necessarily suitable for a carrier grade environment. This dissertation proposes a new failure recovery strategy for SDN, based on existing protocols used in traditional carrier grade networks. The use of segment routing allows for back-up routes to be encoded into the packet header when a failure occurs, without needing to inform other switches of the failure. Back-up routes follow the post-convergence path, meaning that they will not violate traffic engineering constraints on the network. An MPLS (multiprotocol label switching) data plane is used to ensure compatibility with current carrier networks, as MPLS is currently a common protocol in carrier networks. The proposed solution was implemented as a network application, on top of an open-source network operating system. A geographically distributed network testbed was used to verify the suitability for a geographically distributed carrier network. Proof of concept tests showed that the proposed solution provides complete protection for any single link, link aggregate or node failure in the network. In addition, communication latencies in the network do not influence the restoration time, as they do in reactive approaches. Finally, analysis of the back-up path metrics, such as back-up path lengths and number of labels required, showed that the application installed efficient back-up paths