Link-state routing protocol | EPFL Graph Search

Link-state routing protocols are one of the two main classes of routing protocols used in packet switching networks for computer communications, the others being distance-vector routing protocols. Examples of link-state routing protocols include Open Shortest Path First (OSPF) and Intermediate System to Intermediate System (IS-IS). The link-state protocol is performed by every switching node in the network (i.e., nodes that are prepared to forward packets; in the Internet, these are called routers). The basic concept of link-state routing is that every node constructs a map of the connectivity to the network, in the form of a graph, showing which nodes are connected to which other nodes. Each node then independently calculates the next best logical path from it to every possible destination in the network. Each collection of best paths will then form each node's routing table. This contrasts with distance-vector routing protocols, which work by having each node share its routing tabl

Modeling and predicting mobility in wireless ad hoc networks

Jérôme Härri

Wireless Ad Hoc Networks are a particular paradigm where wireless devices communicate in a decentralized fashion, without any centralized infrastructure or decision. In order to avoid a situation where nodes chaotically try to communicate, distributed and localized structures (graphs, trees, etc.) need to be built. Mobility brings challenging issues to the maintenance and to the optimality of such structures. In conventional approaches, structures are adapted to the current topology by each node periodically sending beacon messages, which is a significant waste of network resources. If each node can obtain some a priori knowledge of future topology configurations, it could decide to send maintenance messages only when a change in the topology effectively requires updating the structure. In this Doctoral Thesis, we investigate this approach and define the Kinetic Graphs, a novel paradigm regrouping mobility predictions for a kinetic mobility management, and localized and distributed graph protocols to insure a high scalability. The Kinetic Graph framework is able to naturally capture the dynamics of mobile structures, and is composed of four steps: (i) a representation of the trajectories, (ii) a common message format for the posting of those trajectories, (iii) a time varying weight for building the kinetic structures, (iv) an aperiodic neighborhood maintenance. By following this framework, we show that any structure-based ad-hoc protocol may benefit from the kinetic approach. A significant challenge of Kinetic Graphs comes from prediction errors. In order to analyze them, we illustrate the relationship between the prediction model and the mobility model. We decompose the prediction errors into three metrics: the adequacy between the prediction and the mobility models, the predicability of the mobility model, and the mobility model's realism. Following the framework, we define a kinetic model for the modeling of the trajectories and then analyze the extents of the effects of each error metric and develop solutions in order to reduce them. We finally adapt the Multipoint Relaying (MPR) protocol, used by the Optimized Link State Routing protocol (OLSR), and show the significant improvements that may be obtained by using the Kinetic Graph Framework, even on the very challenging vehicular networks.

EPFL2007

The Performance of Measurement-Based Overlay Networks

Sonja Buchegger, Paolo Scotton

The literature contains propositions for the use of overlay networks to supplement the normal IP routing functions with higher-level information in order to improve aspects of network behavior. We consider the use of such an overlay to optimize the end-to-end behavior of some special tra c ows. Measurements are used both to construct the virtual links of the overlay and to establish the link costs for use in a link-state routing protocol. The overlay attempts to forward certain packets over the least congested rather than the shortest path. We present simulation results showing that contrary to common belief overlay networks are not always bene cial and can be detrimental.

2002

Speed-Aware Routing for UAV Ad-Hoc Networks

Karol Jacek Kruzelecki, Bixio Rimoldi, Stefano Rosati, Louis François Traynard

In this paper we examine mobile ad-hoc networks (MANET) composed by unmanned aerial vehicles (UAVs). Due to the high-mobility of the nodes, these networks are very dynamic and the existing routing protocols partly fail to provide a reliable communication.We present Predictive-OLSR an extension to the Optimized Link-State Routing (OLSR) protocol: it enables efficient routing in very dynamic conditions. The key idea is to exploit GPS information to aid the routing protocol. Predictive-OLSR weights the expected transmission count (ETX) metric, taking into account the relative speed between the nodes. We provide numerical results obtained by a MAC-layer emulator that integrates a flight simulator to reproduce realistic flight conditions. These numerical results show that Predictive-OLSR significantly outperforms OLSR and BABEL, providing a reliable communication even in very dynamic conditions.

2013

Modeling and predicting mobility in wireless ad hoc networks

Jérôme Härri

EPFL2007