A Simple and General Operational Framework to Deploy Optimal Routes with Source Routing

Source Routing, currently facilitated by Segment Routing (SR), enables precise control of forwarding paths by specifying detours (or segments) to deviate IP packets along routes with advanced properties beyond typical shortest IGP paths. Computing the desired optimal segment lists, known as encoding, leads to interesting challenges as the number of detours is tightly constrained for hardware performance. Existing solutions either lack generality, correctness, optimality, or practical computing efficiency-in particular for sparse realistic networks. In this paper, we address all such challenges with GOFOR-SR. Our framework extends usual path computation algorithms to inherently look at optimal and feasible segment lists, streamlining the deployment of TE-compliant paths. By integrating encoding within the path computation itself and modifying the distance comparison method, GOFOR allows algorithms with various optimization objectives to efficiently compute optimal segment lists. Despite the loss of substructure optimality induced by SR, GOFOR proves particularly efficient, inducing only a linear overhead at worst. It also offers different strategies and path diversity options for intricate TE-aware loadbalancing. We formally prove the correctness and optimality of GOFOR, implement our framework for various practical usecases, and demonstrate its performance and benefits on both real and challenging topologies

Computing Delay-Constrained Least-Cost Paths for Segment Routing is Easier Than You Think

With the growth of demands for quasi-instantaneous communication services such as real-time video streaming, cloud gaming, and industry 4.0 applications, multi-constraint Traffic Engineering (TE) becomes increasingly important. While legacy TE management planes have proven laborious to deploy, Segment Routing (SR) drastically eases the deployment of TE paths and thus became the most appropriate technology for many operators. The flexibility of SR sparked demands in ways to compute more elaborate paths. In particular, there exists a clear need in computing and deploying Delay-Constrained Least-Cost paths (DCLC) for real-time applications requiring both low delay and high bandwidth routes. However, most current DCLC solutions are heuristics not specifically tailored for SR. In this work, we leverage both inherent limitations in the accuracy of delay measurements and an operational constraint added by SR. We include these characteristics in the design of BEST2COP, an exact but efficient ECMP-aware algorithm that natively solves DCLC in SR domains. Through an extensive performance evaluation, we first show that BEST2COP scales well even in large random networks. In real networks having up to thousands of destinations, our algorithm returns all DCLC solutions encoded as SR paths in way less than a second

Path computation algorithms in IP networks : reliable hot-potato routing & deployable multi-constrained tunnels

Les travaux présentés dans cette thèse se décomposent en deux parties centrées autour du routage. Nous nous intéressons d'abord aux calculs de chemins multicritères, notamment utiles pour router du trafic exigeant une latence faible. Le problème NP-Difficile étudié, appelé DCLC, devient radicalement plus complexe lorsque l'on considère les contraintes opérationnelles rajoutées par la technologie utilisée pour déployer ces chemins, Segment Routing. Nous proposons différents méthodes et algorithmes afin de résoudre DCLC dans un tel contexte opérationnel, et montrons l'efficacité de nos solutions via une évaluation sur des réseaux large-échelle. Nous nous concentrons ensuite sur les effets néfastes induits par les interactions inter-protocolaires. Les interactions entre BGP (le protocole de routage utilisé dans l'Internet) et l'IGP (utilisé au sein d'un réseau) provoquent un temps de convergence long lors de changements topologiques. Nous retravaillons ces interactions et proposons OPTIC, ramenant ce temps de convergence à une durée marginale. Nous montrons la faisabilité d'OPTIC via évaluation théorique basée sur des données réelles.The work presented in this thesis is divided into two parts centered around routing. First, we focus on multi-criteria path computations, which are particularly useful for routing traffic requiring low latency. The NP-hard problem studied, called DCLC, becomes radically more complex when we consider the operational constraints added by the technology used to deploy these paths, Segment Routing. We propose different methods and algorithms to solve DCLC in such an operational context, and show the efficiency of our solutions via an evaluation on large-scale networks. We then focus on the adverse effects induced by inter-protocol interactions. Interactions between BGP (the routing protocol used in the Internet) and the IGP (used within a network) cause long convergence times during topological changes. We rework these interactions and propose OPTIC, reducing this convergence time to a marginal duration. We show the feasibility of OPTIC via theoretical evaluation based on real data

Calcul de chemins pour réseaux IP : routage de la patate chaude et froide lors de pannes & chemins multi-contraints pour segment routing

The work presented in this thesis is divided into two parts centered around routing. First, we focus on multi-criteria path computations, which are particularly useful for routing traffic requiring low latency. The NP-hard problem studied, called DCLC, becomes radically more complex when we consider the operational constraints added by the technology used to deploy these paths, Segment Routing. We propose different methods and algorithms to solve DCLC in such an operational context, and show the efficiency of our solutions via an evaluation on large-scale networks. We then focus on the adverse effects induced by inter-protocol interactions. Interactions between BGP (the routing protocol used in the Internet) and the IGP (used within a network) cause long convergence times during topological changes. We rework these interactions and propose OPTIC, reducing this convergence time to a marginal duration. We show the feasibility of OPTIC via theoretical evaluation based on real data.Les travaux présentés dans cette thèse se décomposent en deux parties centrées autour du routage. Nous nous intéressons d'abord aux calculs de chemins multicritères, notamment utiles pour router du trafic exigeant une latence faible. Le problème NP-Difficile étudié, appelé DCLC, devient radicalement plus complexe lorsque l'on considère les contraintes opérationnelles rajoutées par la technologie utilisée pour déployer ces chemins, Segment Routing. Nous proposons différents méthodes et algorithmes afin de résoudre DCLC dans un tel contexte opérationnel, et montrons l'efficacité de nos solutions via une évaluation sur des réseaux large-échelle. Nous nous concentrons ensuite sur les effets néfastes induits par les interactions inter-protocolaires. Les interactions entre BGP (le protocole de routage utilisé dans l'Internet) et l'IGP (utilisé au sein d'un réseau) provoquent un temps de convergence long lors de changements topologiques. Nous retravaillons ces interactions et proposons OPTIC, ramenant ce temps de convergence à une durée marginale. Nous montrons la faisabilité d'OPTIC via évaluation théorique basée sur des données réelles

Constrained Backward Time Travel Planning is in P

We consider transportation networks that are modeled by dynamic graphs, and introduce the possibility for traveling agents to use Backward Time-Travel (BTT) devices at any node to go back in time (to some extent, and with some appropriate fee) before resuming their trip. We focus on dynamic line graphs. In more detail, we propose exact algorithms to compute travel plans with constraints on the BTT cost or on how far back in time you can go, while minimizing travel delay (that is, the time difference between the arrival instant and the starting instant), in polynomial time. We study the impact of the BTT devices pricing policies on the computation process of those plans considering travel delay and cost, and provide necessary properties that pricing policies should satisfy to enable to compute such plans. Finally, we provide an optimal online algorithm for the unconstrained problem when the cost function is the identity

Offline Constrained Backward Time Travel Planning

International audienceWe model transportation networks as dynamic graphs and introduce the ability for agents to use Backward Time-Travel (BTT) devices at any node to travel back in time, subject to certain constraints and fees, before resuming their journey.We propose exact algorithms to compute travel plans with constraints on BTT cost or the maximum time that can be traveled back while minimizing travel delay (the difference between arrival and starting times). These algorithms run in polynomial time. We also study the impact of BTT device pricing policies on the computation of travel plans with respect to delay and cost and identify necessary properties for pricing policies to enable such computation

GOFOR-SR: source code and experiments

<p>This repository contains the source code of GOFOR-SR and the script to generate the figures for paper submitted to ToN.</p><p>To run the experiments <strong>with only docker installed:</strong></p><ul><li>download and extract the archive "tar -xzvf archive.tar.gz"</li><li>run the script run-in-docker.sh</li><li>open the jupyter notebook by copying the url printed in the terminal in your favorite browser</li><li>follow the instructions of the notebook</li></ul><p><strong>Note:</strong> On windows, to run docker without mounting a volume, you can read the instruction in the file "run-in-docker.sh"</p><p><strong>Alternatively, you can open the notebook directly, without docker, </strong>just open the notebook in the folder "evaluation/")</p&gt

Constrained Backward Time Travel Planning is in P

We consider transportation networks that are modeled by dynamic graphs, and introduce the possibility for traveling agents to use Backward Time-Travel (BTT) devices at any node to go back in time (to some extent, and with some appropriate fee) before resuming their trip. We focus on dynamic line graphs. In more detail, we propose exact algorithms to compute travel plans with constraints on the BTT cost or on how far back in time you can go, while minimizing travel delay (that is, the time difference between the arrival instant and the starting instant), in polynomial time. We study the impact of the BTT devices pricing policies on the computation process of those plans considering travel delay and cost, and provide necessary properties that pricing policies should satisfy to enable to compute such plans. Finally, we provide an optimal online algorithm for the unconstrained problem when the cost function is the identity

A fast-convergence routing of the hot-potato

Interactions between the intra- and inter-domain routing protocols received little attention despite playing an important role in forwarding transit traffic. More precisely, by default, IGP distances are taken into account by BGP to select the closest exit gateway for the transit traffic (hot-potato routing). Upon an IGP update, the new best gateway may change and should be updated through the (full) re-convergence of BGP, causing superfluous BGP processing and updates in many cases. We propose OPTIC (Optimal Protection Technique for Inter-intra domain Convergence), an efficient way to assemble both protocols without losing the hot-potato property. OPTIC pre-computes sets of gateways (BGP next-hops) shared by groups of prefixes. Such sets are guaranteed to contain the post-convergence gateway after any single IGP event for the grouped prefixes. The new optimal exits can be found through a single walk-through of each set, allowing the transit traffic to benefit from optimal BGP routes almost as soon as the IGP converges. Compared to vanilla BGP, OPTIC's structures allow it to consider a reduced number of entries: this number can be reduced by 99% for stub networks. The update of OPTIC's structures, which is not required as long as border routers remain at least bi-connected, scales linearly in time with its number of groups