Publications

Abstract: This document compares two protocols, MHVB and NHDP. While both protocols are intended for wireless multi-hop ad hoc networks, they differ fundamentally, both in operation and in purpose: MHVB is a location-based, general-purpose transport protocol for network wide information dissemination, whereas NHDP is a protocol enabling a router to acquire information describing its local network topology up to two hops away. Different as they may seem, these two protocols can, in certain situations, serve the same purpose. For example, MHVB can be employed by an ad hoc routing protocol in place of NHDP, for dissemination of topological information when location information is available. Similarly, NHDP may be used to carry certain location-based information, in place of MHVB. This document examines the viability of NHDP and MHVB for neighborhood discovery, and analyses their performance as such. Aside from the usual set of performance parameters, special interest is accorded to the "freshness" of neighborhood information, obtained through each of the protocols.
Category: Research Report

Abstract: MANET routing protocols are designed to scale up to thousands of routers with frequent changes of the topology. In preference, MANET routing protocols should also support constrained low-power devices. One of the bottlenecks of scalability in link-state routing protocols is the performance of the shortest path algorithm (e.g. Dijkstra). In this document, we investigate the in-node performance of OLSRv2 and, in particular, study the benefits of using a dynamic shortest path (DSP) algorithm for this routing protocol. A DSP algorithm is an algorithm that adds or removes edges in the routing tree incrementally and calculates shortest paths, also incrementally. The performance in OLSRv2 with classic Dijkstra vs. DSP is evaluated, by comparing the CPU time for calculating paths in a large emulated network. Additionally, it is demonstrated that frequent topology changes due to mobility in MANETs lead to frequent routing table recalculations with only few routes updated each time. This property of MANETs makes the use of a DSP in OLSRv2 appropriate.
Category: Research Report

Abstract: This document presents a modification of the existing tool AgentJ which allows for running a Java routing protocol within the network simulator NS2.
Category: Research Report

Abstract: A number of efforts currently aim at scalable and efficient mobile ad hoc routing, an essential piece concerning the integration of such networks in the Internet. However, there is another independent and important issue,
namely, how can existing Internet networks and ad hoc networks co-exist coherently within the same protocol architecture. A fundamental concept in the IP protocol suite is that of a link. The link concept has so far been key to the scalability of IP networking. This paper identifies and discusses issues regarding the formalisation of a similar concept in the multi-hop
ad hoc networking context -- one of the first steps that must be taken in the near future, in order to be able to accomodate ad hoc networks in the Internet.
Category: Conference

Abstract: Incorporating multi-hop ad hoc wireless networks in the IP infrastructure is an effort to which a growing community participates. One instance of such activity is the extension of the most widely deployed interior gateway routing protocol on the Internet, OSPF, for operation on MANETs. Such extension allows OSPF to work on heterogeneous networks encompassing both wired and wireless routers, which may self-organize as multi-hop wireless subnetworks, and be mobile. Three solutions have been proposed for this extension, among which two based on techniques derived from multi-point relaying (MPR). This paper analyzes these two approaches and identifies some fundamental discussion
items that pertain to adapting OSPF mechanisms to multihop wireless networking, before concluding with a proposal for a unique, merged solution based on this analysis.
Category: Conference

Abstract: The Internet Engineering Task Force was the birthplace of today’s Internet. Understanding its activities is necessary for individuals and institutions who wish to anticipate the future of the Internet. As things stand, this necessity is not likely to fade any time soon.
Category: Journal

Abstract: This document describes a general and flexible TLV (type-length-value structure) for representing time-values, such as an interval or a duration, using the generalized Mobile Ad hoc NETwork (MANET) packet/message format. It defines two Message TLVs and two Address Block TLVs for representing validity and interval times for MANET routing protocols.
Category: Standard - IETF

Abstract: This memorandum describes a pragmatic set of configuration recommendations for MANETs, as well as provides a rationale for why these recommendations are sound. While there may be other equally valid ways of configuring a MANET, the recommendations in this memorandum have the merit of being supported by an existence proof (there’re running networks in existence, configured according to these recommendations), and they require neither modifications to the IP stack nor to upper-layer protocols or applications.
Category: Research Report

Abstract: Incorporating multi-hop wireless networks in the IP infrastructure is an effort to which a growing community participates. One instance of such activity is the extension of the routing protocol OSPF, for operation on MANETs. Such extension allows OSPF, the most widely deployed interior gateway routing protocol on the Internet, to work on heterogeneous networks encompassing both wired and wireless routers. The latter may self-organize as multi-hop wireless subnetworks, and may be mobile. Three solutions have been proposed for this extension, among which two based on techniques derived from multi-point relaying (MPR) techniques and OLSR. This paper analyzes these two approaches and identifies some fundamental discussion items that pertain to adapting OSPF mechanisms to multi-hop wireless networking, before concluding with a proposal for a unique, merged solution based on this analysis.
Category: Research Report

Abstract: This document specifies an OSPFv3 interface type tailored for mobile ad hoc networks. This interface type is derived from the broadcast interface type, and is denoted the "OSPFv3 MANET interface type".
Category: Standard - IETF

Abstract: This document specifies a packet format capable of carrying multiple messages that may be used by mobile ad hoc network routing protocols.
Category: Standard - IETF

Abstract: The OSPF routing protocol is currently the predominant IGP in use on the fixed Internet of today. This routing protocol scales ``world wide", under the assumptions of links being relatively stable, network density being rather low (relatively few adjacencies per router) and mobility
being present at the edges of the networks only. Recently, work has begun towards extending the domain of OSPF to also include ad-hoc networks --
i.e. dense networks, in which links are short-lived and most nodes are mobile. In this chapter, we focus on the convergence of the Internet and ad-hoc
networks, through extensions to the OSPF routing protocol. Based on WOSPF, a merger of the ad-hoc routing protocol OLSR and OSPF, we examine the
feature of OSPF database exchange and reliable synchronisation in the context of ad-hoc networking. We find that the mechanisms, in the form
present in OSPF, are not suitable for the ad-hoc domain. We propose an alternative mechanism for link-state database exchanges in wireless ad-hoc
networks, aiming at furthering an adaptation of OSPF to be useful also on ad-hoc networks, and evaluate our alternative against the mechanism found
in OSPF. Our proposed mechanism is specified with the following applications in mind: (i) Reliable diffusion of link-state information replacing OSPF acknowledgements with a mechanism suitable for mobile wireless networks; (ii) Reduced overhead for performing OSPF style database exchanges in a mobile wireless network; (iii) Reduced initialisation time when new nodes are emerging in the network; (iv) Reduced overhead and reduced convergence time when several wireless OSPF ad
hoc network clouds merge.

Abstract: This document analyses the MPR-OSPF current specification and compares it with the implemented version for the Quagga / Zebra routing suite, adapted for the GTNetS network simulator. It presents the relationship between Quagga/Zebra core and the GTNetS simulation framework, describes the inner architecture of the MPR-OSPF extension in the OSPF Quagga general implementation and identifies the different protocol main elements in the implemented code.
Category: Research Report

Abstract: This note describes the architecture of our implementation
of OLSRv2 in Java, and some extensions
thereto.
Category: Conference

Abstract: In the near-future, self-organized networking is expected to become an important component in ITS, and in the Internet architecture in general. An essential challenge concerning the integration of this new component
is the accomplishment of scalable and efficient mobile ad
hoc routing. This paper overviews considerations relative to the design of such MANET protocols inside the framework provided by the IETF, stating the need for new hybrid protocols and architecture which offer a gradual transition from �traditional� MANET routing towards scalable MANET routing integrated in the Internet. This paper also proposes a tentative solution in this domain: DHT-OLSR, based on OLSR enhanced with dynamic clustering and distributed hash table
routing.
Category: Conference

Abstract: Abstract Network coding is a novel method for transmitting data, which has been recently proposed. In this article, we study using network coding for one
specific case of multicast, broadcasting. Precisely, we focus on (energy-) efficient broadcasting in a multi-hop wireless networks: transmitting data from
one source to all nodes with a small number of retransmissions. It is known that the efficiency of network coding is essentially determined by the selected
rates of each node. Our contribution is to propose a simple and efficient method for determining a rate selection. Our method adapts dynamically and uses only local dynamic information of neighbors: Dynamic Rate Adaptation from Gap with Other Nodes (D.R.A.G.O.N.). The rationale of this rate selection method is detailed from some logical arguments. Experimental results illustrate the behavior of the method, and its excellent performance.

Abstract: This document provides recommendations for jittering (randomly modifying timing) of control traffic transmissions in Mobile Ad hoc NETwork (MANET) routing protocols to reduce the probability of transmission collisions. This memo provides information for the Internet community.


Category: Standard - IETF

Abstract: This memorandum outlines the goals for and constraints on an IP address and prefix autoconfiguration mechanism for mobile ad hoc networks.
Category: Research Report

Abstract: Multicast is a central challenge for emerging multi-hop wireless architectures such as wireless mesh networks, because of its substantial cost in terms of bandwidth. In this article, we study one specific case of multicast: broadcasting, sending data from one source to all nodes, in a multi-hop wireless network. The broadcast we focus on is based on network coding, a promising avenue for reducing cost; previous work of ours showed that the performance of network coding with simple heuristics is asymptotically optimal:
each transmission is beneficial to nearly every receiver.
This is for homogeneous and large networks of the plan. But for small, sparse or for inhomogeneous networks, some additional heuristics are required. This article proposes such additional new heuristics (for selecting rates) for broadcasting with network coding. Our heuristics are intended to use only simple local topology information. We detail the logic of the heuristics, and with experimental results, we illustrate the behavior of the heuristics, and demonstrate their excellent performance.
Category: Conference

Abstract: MANET networks are of prime interest for military networks. One of the proeminent routing protocols for MANET is OLSR, and indeed, OLSR has been used in many evaluations and experiments of MANETs. As OLSR is on its way to standardization, there are still a number of extensions that are useful and sometimes necessary for practical use of OLSR networks: such extensions are quality of service support (QoS), security, and OSPF interconnection. In this paper, we present the archictecture, design, specifications and implementations that we made to integrate these features in a military
testbed. This testbed is a real MANET comprising 18 nodes. These nodes communicate by radio and use the IEEE 802.11b MAC protocol. The OLSR routing protocol updates the routing table used by the IP protocol to forward packets.
Category: Conference

Abstract: We address the problem of efficient broadcasting in multi-hop wireless networks with network coding. Network coding was introduced by the seminal work of [1] as a new paradigm where intermediate nodes are mixing information from different flows (different bits or different packets). The problem that we are addressing
is efficient broadcast, precisely:
• Broadcast packets from one source to all nodes, with the minimum number of transmissions.
Without network coding, finding the optimal solution is an NP complete problem. With network coding, essentially, nodes will retransmit coded packets with an average interval, defining a node rate. Finding an optimal solution consists in finding the coding nodes and their optimal rates. This can be formulated as a linear program, which can be solved in polynomial time [2]. However, we adopt a different, even simpler, approach:
our previous work [3, 4] has shown a simple heuristic could achieve asymptotically the optimal efficiency for homogeneous large and dense wireless networks of the plane � and also that, noticeably, it outperforms methods not using network coding. This is true asymptotically, and for homogeneous networks. The heuristic need adjustments for less homogeneous, smaller or sparser networks, the topic of the poster. Our key contributions are the following:
• We propose an improved heuristic for rate selection, inspired by [5]. It is based only on local topology information: knowledge of two-hop neighbors.
• We study its performance on representative graphs with different densities (using min-cut calculation).
We investigate and explain the variation of the performance.
Category: Conference

Abstract: We study efficient broadcasting for wireless sensor networks, with network coding. We address this issue for homogeneous sensor networks in the plane. Our results are based on a simple principle (IREN/IRON),
which sets the same rate on most of the nodes (wireless links) of the network. With this rate selection, we give a value of the maximum achievable broadcast rate of the source: our central result is a proof of the value of the min-cut for such networks, viewed as hypergraphs. Our metric for efficiency is the number of transmissions necessary to transmit one packet from the source to every destination: we show that IREN/IRON achieves near optimality for large networks; that is, asymptotically, nearly every transmission brings new information from the source to the receiver. As a consequence, network coding asymptotically outperforms any scheme that does not use network coding.
Category: Conference

Abstract: Recently, various working groups of standardization
bodies, have finalized or have been finalizing standards
for wireless mesh networks (WMNs), which will provide
some ad-hoc network capabilities to wireless networks. An example is the task group “S�, 802.11s, focusing on mesh extensions for Wi-Fi networks. Such networks accommodate two kinds of nodes: mesh routers which form networks automatically in a similar fashion to ad-hoc networks ; and mesh clients which can simply associate with these mesh routers to access to the
rest of the network. Because of the discrepancy of behavior between mesh routers and mesh clients, WMNs have a hybrid structure, where the mesh routers form a backbone, and where clients have no routing capability. Routing in WMNs may be achieved with an extension of routing with two levels of information: traditional routing tables between mesh routers, complemented with association tables for linking mesh clients to mesh routers.
For the first level, routing between mesh routers, can be
used, for instance modified versions of MANET protocols.
For the second level, we propose an Association Discovery Protocol (ADP): it allows each mesh router to determine where are located the other stations.
Our proposal had actually been integrated in the early
802.11s proposals [6], and in this article, our focus will be on such 802.11 mesh networks.
Because the ADP has parameters which can be tuned,
a performance analysis of the protocol is essential. In this article, we describe this protocol, and provide an analytic model of its performance. The performance evaluation is confirmed by simulation results.
Category: Conference

Abstract: Solutions for mobile ad hoc routing have matured over the last decade. Building atop these foundations, new challenges are set for MANETs, such as integration in the Internet core. On this topic, this paper designs and evaluates MPR-OSPF, an extension of the OSPF protocol enabling its operation on networks that may include both MANET nodes and usual fixed routers. Automatic integration of different types of vehicular ad hoc networks (VANETs) in the IP infrastructure is then possible using the classic OSPF framework. Techniques used therefore are derived from OLSR, the MANET routing protocol that is the most compatible with traditional IP environments.

Category: Conference

Abstract: Self-organized networking is foreseen as an important component in the Internet’s near-future architecture. An essential challenge concerning the integration of this new component is the accomplishment of scalable and efficient ad hoc routing. This report proposes a new solution in this space, DHT-OLSR, based on OLSR enhanced with dynamic clustering and distributed hash table (DHT) routing. We believe that such a protocol can provide an architecture that may introduce a gradual transition from traditional IP routing towards scalable IP MANET
routing.
Category: Conference

Abstract: This memorandum describes a common misperception concerning MANETs and their underlying network architecture when integrating into classic IP networks. It
details the consequences of this misperception - breaking compatibility with existing applications and protocols - and offers an architectural model for MANETs which integrate well into the IP Networking Architecture.
Category: Research Report

Abstract: The Internet uses hierarchical networking, for scalability
and manageability reasons. However the main ad hoc
routing solutions (OLSR [1], AODV [6], DSR [8], TBRPF
[7]) only provide flat networking, and generally suffer im-
portant scalability issues. This paper therefore introduces
a simple mechanism providing dynamic clustering with
OLSR, one of the MANET routing solutions, chosen for
its easy integration in the Internet infrastructure. The paper
then describes how this dynamic clustering can be used to
provide MANET hierarchical networking with OLSR.
Category: Conference

Abstract: Commonly, duplicate address detection is performed
when configuring network interfaces in order to ensure
that unique addresses are assigned to each interface in
the network. Such mechanisms commonly operate with
the premises that a node �intelligently� selects an address
which it supposes to be unique, followed by a duplicate address detection cycle, through which it verifies that no other active interfaces on the same network has been or is in the process of being configured with the same address. Even assuming that such a mechanism is present in a MANET, allowing MANET nodes to initially configure their interfaces with addresses unique within the network, additional complications arise: two or more MANETs may merge to form a single network, and a formerly connected MANET may partition. Thus, unless it is ensured that all MANET interfaces are assigned globally unique addresses, addressing conflicts may at any point – not just during initial network configuration.
In this paper, we investigate the task of performing dupli-
cate address detection when otherwise independent OLSR networks merge. We benefit from the information already exchanged by OLSR, and identify a number of mechanisms through which a node may detect a conflict between the address assigned to one of its interfaces, and an address assigned to an interface on another node. The mechanisms proposed are, thus, entirely passive, creating no additional information exchange on the network.
Category: Conference

Abstract: Using reduced topology within link state routing has proven to be an efficient way to decrease routing overhead while still providing sufficient route quality. There are various ways to achieve topology reduction, based on different ways to form a backbone in the network this backbone usually originates from the flooding optimization scheme in use, such as MPR or CDS. In case of mobile ad hoc networks, flooding using MPR backbones is preferable as it is more robust in face of topology changes, compared to flooding using CDS backbones. This text therefore describes several methods to enable the use of reduced topology in wireless OSPF for MANETs, when MPR-based flooding optimizations are used. The topology reduction methods that are proposed for MPR-based approaches perform at least as well as the similar schemes that were recently proposed for CDS-based apporaches.
Category: Research Report

Abstract: We investigate in this paper the effect of mobility, collisions and obsolete informations on the performance of connected dominating set (CDS). In particular we show that neighbor-designated CDS such as multipoint relay (MPR) as are in general more robust than self-selected CDS such as rule k CDS. This is particularly crucial in application such as wireless OSPF where third party topology informations may take arbitrary delay
Category: Research Report

Abstract: The main ad hoc routing protocols that were proposed generally provide only flat networks. However the Internet has always been of a hierarchical nature, for scalability and manageability reasons. This paper therefore introduces a simple mechanism providing dynamic clustering with OLSR, one of the MANET routing solutions, chosen for its ease of integration in the Internet infrastructure. This clustering can have many different applications. This work describes how it can be used to provide hierarchical routing with OLSR.
However, it is not limited to this use.
Category: Conference

Abstract: In this paper, we develop a simple autoconfiguration mechanism for OLSR networks. The mechanism aims at solving the simple, but common, probem of one or more new nodes emerging in an existing network. We propose a simple solution, which allows these new nodes to acquire an address and participate in the network. Our method is simple, both algorithmically and in the requirements to the network. While we recognize that this is a partial solution to the general autoconfiguration problem, we argue that the mechanism described in this paper will satisfy the requirements from a great number of real-world situations.
Category: Conference

Abstract: Internet edge mobility has been possible for a number of
years: mobile IP[8], allows a host to change its point of attachment to the Internet and NEMO [6] allows the same
functionality for a group of hosts along with a mobile
router. The virtue of NEMO and mobile IP is transparency: a host remains identifiable through the same IP address, and traffic sent to that IP address will be tunneled to arrive at the intended node. NEMO allows “nested networks�: a mobile network which attaches to another mobile network to arbitrary depth. However for each level of nesting, traffic is encapsulated and tunneled to reach the destination. This leads to increased overhead (encapsulation) and to sub-optimal
paths (tunneling without consideration for the actual net-
work topology). In this paper, we investigate route-optimization in nested NEMO networks. We employ an ad-hoc routing protocol between mobile routers to ensure shortest routes when both source and destination for traffic is within the nested NEMO network. The mechanism also simplifies the requirements for route optimization when the source node is located outside of the nested NEMO network.
Category: Conference

Abstract: The primary issue with respect to securing Mobile Ad hoc NETworks (MANETs) is that of ensuring network integrity even when the network is subject to attacks to break its connectivity. In this research report, we study how to secure the OLSR routing protocol . We first analyse the attacks that can be launched against the network integrity. We then present mechanisms for ensuring that only ``trusted'' nodes are admitted into the network and, subsequently, are the only nodes used to forward traffic. We also present mechanisms for detecting and dealing with scenarios where ``trusted'' nodes have become compromised.
Category: Research Report

Abstract: Scalability is one of the toughest challenges in ad hoc
networking. Recent work outlines theoretical bounds on how well routing protocols could scale in this environment. However, none of the popular routing solutions really scales to large networks, by coming close enough to these bounds. In this paper, we study the case of link state routing and OLSR, one of the strongest candidate for standardization. We analyze how these bounds are not reached in this case, and we study how much the scalability is enhanced with the use of Fish Eye techniques in addition to the link state routing framework. We show that with this enhancement, the theoretical scalability bounds are reached.
Category: Journal

Abstract: The Optimized Link-State Routing protocol
(OLSR) is a proactive link-state routing protocol. While
similar to the well-known Internet routing protocol OSPF,
OLSR is designed to be simple, and to maintain connec-
tivity in face of highly dense and dynamic networks, while
being ressource-economic (battery, bandwidth etc.) These characteristics make OLSR suitable as an underlaying routing protocol in a wide range of ad-hoc sensor networks. In this paper, we introduce an extension to OLSR: OSPF-style database exchange and reliable synchronization. The goal of this extension is to provide a mechanism, through which nodes in an ad-hoc sensor network can detect and correct discrepancies in their link-state databases. We qualify why the mechanism, found in OSPF, is not directly applicable for ad-hoc sensor networks, describe an adopted mechanism, accomplishing the same goal, and evaluate the performance of this mechanism in comparison to the database exchange mechanism found in OSPF. We finally discuss some applications of database exchange and reliable synchronization in ad-hoc sensor networks.
Category: Conference

Abstract: Scarce bandwidth and interferences in mobile ad-hoc
networks yield the need for more efficient diffusion
techniques than these employed on usual wired networks,
especially in dense environments. In this paper, we
compare some optimized flooding mechanisms that were
proposed in view to gain enough performance and allow
applications such as multimedia diffusion in an ad hoc
environment. We namely present multi-point relay (MPR)
flooding and gateway flooding. We investigate the matter
theoretically via mathematical modelling, as well as practically via simulations. It is shown how well each of these techniques improve the diffusion performances: when the network is dense, 2/3 of the gateway nodes participate in the retransmissions, while the density of multi-point relay retransmitters is 1/v , where v is the node density.
Category: Conference

Abstract: This paper proposes a general, parameterized model
for analyzing protocol control overhead in mobile ad-hoc networks. A probabilistic model for the network topology and the data traffic is proposed in order to estimate overhead due to control packets of routing protocols.
Our analytical model is validated by comparisons with simulations, both taken from literature and made specifically for this paper. For example, our model predicts linearity of control overhead with regard to mobility as observed in existing simulations results. We identify the model parameters for protocols like AODV, DSR and OLSR.

Our model then allows accurate predictions of which protocol will yield the lowest overhead depending on the node mobility and traffic activity pattern.
Category: Journal

Abstract: The Optimized Link-State Routing protocol (OLSR) is a proactive link-state routing protocol. While similar to the well-known Internet routing protocol OSPF, OLSR is designed to be simple, and to maintain connectivity in face of highly dense and dynamic networks, while being ressource-economic (battery, bandwidth etc.) These characteristics make OLSR suitable as an underlaying routing protocol in a wide range of ad-hoc sensor networks. In this paper, we introduce an extension to OLSR: OSPF-style database exchange and reliable synchronization. The goal of this extension is to provide a mechanism, through which nodes in an ad-hoc sensor network can detect and correct discrepancies in their link-state databases. We qualify why the mechanism, found in OSPF, is not directly applicable for ad-hoc sensor networks, describe an adopted mechanism, accomplishing the same goal, and evaluate the performance of this mechanism in comparison to the database exchange mechanism found in OSPF. We finally discuss some applications of database exchange and reliable synchronization in ad-hoc sensor networks.
Category: Research Report

Abstract: In this paper, we describe the Optimized Link State Routing Protocol (OLSR), a proactive routing protocol for Mobile Ad-hoc NETworks (MANETs). We evaluate its performance through exhaustive simulations using the Network Simulator 2 (ns2), and compare with other ad-hoc protocols, specifically the Ad-hoc On-Demand Distance Vector (AODV) routing protocol and the Dynamic Source Routing (DSR) protocol. We study the protocols under varying conditions (node mobility, network density) and with varying traffic (TCP, UDP, different number of connections/streams) to provide a qualitative assessment of the applicability of the protocols in different scenarios.
Category: Research Report

Abstract: In this paper, we specify a mechanism for link-state database exchanges in wireless ad-hoc networks. The mechanism is taylored for ad-hoc networks employing the wireless OSPF interface extension specification , however is suitable for any proactive link-state routing protocol.The database exchange mechanism is specified with the following applications in mind: reliable diffusion of link-state information, replacing OSPF acknowledgements with a mechanism, suitable for mobile wireless networks; reduced overhead for performing OSPF style database exchanges in a mobile wireless network; reduced initialization time when new node(s) are emerging in the network; reduced overhead and reduced convergence time when two (or more) WOSPF adhoc network clouds merge.
Category: Research Report

Abstract: Link state has been the dominating IGP routing technology in IP networks for more than a decade. With the advent of wireless ad-hoc networking, the need for light, efficient and robust routing makes it a good candidate to be also used in this constrained environment. One of the key issue in ad-hoc networking is the lack of bandwidth. Thus, in this paper we examine the overhead due to link state routing in an ad-hoc network. More precisely we study the classic link-state protocol OSPF and OLSR, a link state protocol that was developed specifically for ad-hoc networks. Further, we study how this overhead evolves when the node density increases. The last part of the paper presents directions towards extending OSPF for wireless and ad-hoc networks, which would make it a favorite to seamlessly unify wired and mobile IP networks.
Category: Conference

Abstract: This document describes the Optimized Link State Routing (OLSR) protocol for mobile ad hoc networks. The protocol is an optimization of the classical link state algorithm tailored to the requirements of a mobile wireless LAN. The key concept used in the protocol is that of multipoint relays (MPRs). MPRs are selected nodes which forward broadcast messages during the flooding process. This technique substantially reduces the message overhead as compared to a classical flooding mechanism, where every node retransmits each message when it receives the first copy of the message. In OLSR, link state information is generated only by nodes elected as MPRs. Thus, a second optimization is achieved by minimizing the number of control messages flooded in the network. As a third optimization, an MPR node may chose to report only links between itself and its MPR selectors. Hence, as contrary to the classic link state algorithm, partial link state information is distributed in the network. This information is then used for route calculation. OLSR provides optimal routes (in terms of number of hops). The protocol is particularly suitable for large and dense networks as the technique of MPRs works well in this context.
Category: Standard - IETF

Abstract: This document describes the Multicast extension for the Optimized Link State Routing protocol (MOLSR). MOLSR is in charge of building a multicast structure in order to route multicast traffic in an ad-hoc network. MOLSR is designed for mobile multicast routers, and works in a heterogenous network composed of simple unicast OLSR routers, MOLSR routers and hosts. In the last part of this document we introduce also a Wireless Internet Group Management Protocol (WIGMP). It offers the possibility for OLSR nodes (without multicast capabilities) to join multicast groups and receive multicast data.
Category: Research Report

Abstract: Many protocols for Mobile Ad-hoc Networks such as AODV propose construction routes reactively using flooding. The advantage hereof is, that no prior assumptions of the network topology are required in order to provide routing between any pair of nodes in the network. In mobile networks, where the topology is subject to frequent changes, this is a particularly attractive property. In this paper, we investigate the effect of using flooding for acquiring routes. We show, that flooding may lead to non-optimal routes in terms of number of hops. This implies that more retransmissions are needed to send a packet along a route. We proceed by providing a qualitative analysis of the route lengths. Finally, we propose and evaluate through simulations, alternative flooding schemes such as MPR flooding and Suoerflooding. MPR flooding considerably reduces the flooding overhead and provides shorter routes very close to optimal. Superfloo- ding provides optimal routes but to the cost of an significant but anyhow reasonable increase of flooding overhead.
Category: Research Report