Amund Kvalbein

Fast IP Network Recovery Using Multiple Routing Configurations

As the Internet takes an increasingly central role in our communications infrastructure, the slow convergence of routing protocols after a network failure becomes a growing problem. To assure fast recovery from link and node failures in IP networks, we present a new recovery scheme called Multiple Routing Configurations (MRC). MRC is based on keeping additional routing information in the routers, and allows packet forwarding to continue on an alternative output link immediately after the detection of a failure. Our proposed scheme guarantee s recovery in all single failure scenarios, using a single mechanism to handle both link and node failures, and without knowing the root cause of the failure. MRC is strictly connectionless, and assumes only destination based hop-by-hop forwarding. It can be implemented with only minor changes to existing solutions. In this paper we present MRC, and analyze its performance with respect to scalability, backup path lengths, and load distribution after a failure.

Multiple routing configurations for fast IP network recovery

As the Internet takes an increasingly central role in our communications infrastructure, the slow convergence of routing protocols after a network failure becomes a growing problem. To assure fast recovery from link and node failures in IP networks, we present a new recovery scheme called Multiple Routing Configurations (MRC). Our proposed scheme guarantees recovery in all single failure scenarios, using a single mechanism to handle both link and node failures, and without knowing the root cause of the failure. MRC is strictly connectionless, and assumes only destination based hop-by-hop forwarding. MRC is based on keeping additional routing information in the routers, and allows packet forwarding to continue on an alternative output link immediately after the detection of a failure. It can be implemented with only minor changes to existing solutions. In this paper we present MRC, and analyze its performance with respect to scalability, backup path lengths, and load distribution after a failure. We also show how an estimate of the traffic demands in the network can be used to improve the distribution of the recovered traffic, and thus reduce the chances of congestion when MRC is used.

Post-Failure Routing Performance with Multiple Routing Configurations

The slow convergence of IGP routing protocols after a topology change has led to several proposals for proactive recovery schemes in IP networks. These proposals are limited to guaranteeing loop-free connectivity after a link or node failure, and do not take into account the resulting load distribution in the network. This can lead to congestion and packet drops. In this work, we show how a good load distribution can be achieved in pure IP networks immediately after a link failure, when multiple routing configurations (MRC) is used as a fast recovery mechanism. This paper is the first attempt to improve the load balancing when a proactive recovery scheme is used. Unlike load balancing methods used with normal IP rerouting, our method does not compromise on the routing performance in the failure free case. Our method is evaluated using simulations on several real and synthetically generated network topologies. The evaluation shows that our method yields good routing performance, making it feasible to use MRC to handle transient network failures.

Loop-free alternates and not-via addresses: A proper combination for IP fast reroute?

The IETF currently discusses fast reroute mechanisms for IP networks (IP FRR). IP FRR accelerates the recovery in case of network element failures and avoids micro-loops during re-convergence. Several mechanisms are proposed. Loop-free alternates (LFAs) are simple but cannot cover all single link and node failures. Not-via addresses can protect against these failures but are more complex, in particular, they use tunneling techniques to deviate backup traffic. In the IETF it has been proposed to combine both mechanisms to merge their advantages: simplicity and full failure coverage. This work analyzes LFAs and classifies them according to their abilities. We qualitatively compare LFAs and not-via addresses and develop a concept for their combined application to achieve 100% single failure coverage, while using simple LFAs wherever possible. The applicability of existing LFAs depends on the resilience requirements of the network. We study the backup path length and the link utilization for both IP FRR methods and quantify the decapsulation load and the increase of the routing table size caused by not-via addresses. We conclude that the combined usage of both methods has no advantage compared to the application of not-via addresses only.

Fast recovery from link failures using resilient routing layers

We present a novel scheme for network recovery, named resilient routing layers (RRL). Our proposed scheme is based on calculating fully connected topology subsets, termed layers, which are used to forward traffic in case of a network failure. For the purpose of this work, the layers are created to protect against link failures only. RRL keeps pre-calculated backup routing information in the network stations. This allows local response to network failures, which gives recovery in the order of milliseconds. The main strengths of our approach are its flexibility, as it is independent of the network technology used, and its simplicity, as it offers the network operator a simple and coherent view of the resources available after a link failure. We also show that our scheme scales well for networks of several hundred nodes.

Fast recovery from dual-link or single-node failures in IP networks using tunneling

This paper develops novel mechanisms for recovering from failures in IP networks with proactive backup path calculations and Internet Protocol (IP) tunneling. The primary scheme provides resilience for up to two link failures along a path. The highlight of the developed routing approach is that a node reroutes a packet around the failed link without the knowledge of the second link failure. The proposed technique requires three protection addresses for every node, in addition to the normal address. Associated with every protection address of a node is a protection graph. Each link connected to the node is removed in at least one of the protection graphs, and every protection graph is guaranteed to be two-edge-connected. The network recovers from the first failure by tunneling the packet to the next-hop node using one of the protection addresses of the next-hop node; the packet is routed over the protection graph corresponding to that protection address. We prove that it is sufficient to provide up to three protection addresses per node to tolerate any arbitrary two link failures in a three-edge-connected graph. An extension to the basic scheme provides recovery from single-node failures in the network. It involves identification of the failed node in the packet path and then routing the packet to the destination along an alternate path not containing the failed node. The effectiveness of the proposed techniques were evaluated by simulating the developed algorithms over several network topologies.

Multipath load-adaptive routing: putting the emphasis on robustness and simplicity

We propose a routing and load-balancing approach with the primary goal of being robust to sudden topological changes and significant traffic matrix variations. The proposed method load-balances traffic over several routes in an adaptive way based on its local view of the load in the network. The focus is on robustness and simplicity, rather than optimality, and so it does not rely on a given traffic matrix, nor it is tuned to a specific topology. Instead, we aim to achieve a satisfactory routing under a wide range of traffic and topology scenarios based on each nodes independent operation. The scheme avoids the instability risks of previous load-responsive routing schemes, it does not load the control plane with congestion-related signaling, and it can be implemented on top of existing routing protocols. In this paper, we present the proposed scheme, discuss how it aims to meet the objectives of robustness and load-responsiveness, and evaluate its performance under diverse traffic loads and topological changes with flow-level simulations.

An empirical comparison of generators for self similar simulated traffic

It is generally recognised that aggregated network traffic is self similar and that self similar traffic models should be used in simulation experiments when assessing the performance of a network. Many generators have been proposed to synthetically produce self similar simulation input; however most of them require the trace length to be known a priori. Four generators that allow continuous generation of self similar time series are evaluated in this work with respect to their ability to reproduce the desired level of self similarity. This extensive investigation uses ten times as many traces and twice the number of parameter values as previously reported. Three of the tested generators perform well but surprisingly the generator supplied with a widely used commercial network simulator is unusable. The reported results indicate that the generator based on multiplexing strictly alternating ON/OFF sources may perform better than generators based on chaotic maps, provided that more than 100 ON/OFF sources can be used. Three estimators for the degree of self similarity of a time series have been evaluated as part of the process, and the only acceptable one is based on a Wavelet decomposition of the traffic trace.

The Nornet Edge platform for mobile broadband measurements

We present Nornet Edge (NNE), a dedicated infrastructure for measurements and experimentation in mobile broadband networks. NNE is unprecedented in size, consisting of more than 400 measurement nodes geographically distributed all over Norway. Each measurement node is a Linux-based embedded computer, and is connected to multiple mobile broadband providers. In addition, NNE includes an extensive backend system for deploying and managing experiments and collecting data. NNE makes it possible to run long-term measurement experiments to assess and compare quality and performance across different network operators on a national scale. Particular focus is put on allowing experiments to run in parallel on multiple network connections, and on collecting rich context information related to the experiments. In this paper we give a detailed presentation of NNE, and describe three different measurement experiments that illustrate how the infrastructure can be used. We also provide a roadmap for further development of NNE.

NorNet Core - A multi-homed research testbed

Over the last decade, the Internet has grown at a tremendous speed in both size and complexity. Nowadays, a large number of important services - for instance e-commerce, healthcare and many others - depend on the availability of the underlying network. Clearly, service interruptions due to network problems may have a severe impact. On the long way towards the Future Internet, the complexity will grow even further. Therefore, new ideas and concepts must be evaluated thoroughly, and particularly in realistic, real-world Internet scenarios, before they can be deployed for production networks. For this purpose, various testbeds - for instance PlanetLab, GpENI or G-Lab - have been established and are intensively used for research. However, all of these testbeds lack the support for so-called multi-homing.Multi-homing denotes the connection of a site to multiple Internet service providers, in order to achieve redundancy. Clearly, with the need for network availability, there is a steadily growing demand for multi-homing. The idea of the NorNet Core project is to establish a Future Internet research testbed with multi-homed sites, in order to allow researchers to perform experiments with multi-homed systems. Particular use cases for this testbed include realistic experiments in the areas of multi-path routing, load balancing, multi-path transport protocols, overlay networks and network resilience. In this paper, we introduce the NorNet Core testbed as well as its architecture.