Christoph Barz

A case for research with and on community networks

Community Networks are large scale, self-organized and decentralized networks, built and operated by citizens for citizens. In this paper, we make a case for research on and with community networks, while explaining the relation to Community-Lab. The latter is an open, distributed infrastructure for researchers to experiment with community networks. The goal of Community-Lab is to advance research and empower society by understanding and removing obstacles for these networks and services.

OLSRv2 for Community Networks

In this paper we present novel approaches to routing in Community Networks. We combine recent advances in OLSR development regarding modularization, scalability, extensibility, and metrics with a node architecture concept based on radio and router separation adopted to Community Networks. This node architecture consists of a single router with several external radios acting as wireless bridges and connecting to the router via standard Ethernet, which we refer to as Hybrid Node Design. Furthermore, we propose the use of our Directional Airtime (DAT) routing metric that is suitable for the heterogeneous link characteristics often found in Community Networks. By using this metric we achieve a more stable route selection process and improved throughput in comparison to the OLSR-based approach currently used in Community Networks. In addition, we present some enhanced features unique to our implementation that include means to increase the self-configuration capabilities in IPv4, IPv6, and dual-stack configurations. As a consequence, we recommend that it is the right time for Community Networks to start the migration process from OLSRv1 to OLSRv2.For the implementation process and the protocol evaluation we followed a testbed-driven approach. It was supported by the Confine testbed both, in a virtualized version, as well as in a physical deployment in a dense setup at Fraunhofer FKIE. The physical testbed consists of over 20 indoor research nodes on two floors implementing our hybrid node design. Link layer information from the radio devices to the router is provided by the DLEP protocol, which was designed especially for wireless mesh networks. The obtained link layer information is used by OLSRv2 for routing metric computation. We propose the use of this architecture in Community Networks in order to increase scalability and simplify network administration.

Improved community network node design using a DLEP based radio-to-router interface

Using a static link state routing metric in wireless mesh and mobile ad hoc networks without major efforts in optimizing the physical link properties has proven to be inefficient. It does not take into account link quality information. While some link metrics try to estimate channel properties based on layer-3 observations, more sophisticated metrics need to access layer-2 information directly. The new 802.11 netlink interface provides a common local interface for Linux based systems and thus the basis for practical usage in community networks. However, a standardized radio-to-router communication protocol to access layer-2 information will allow to go beyond the limitations of having all radio interfaces built directly into the router device. While the PPPoE protocol generally can be applied to this scenario, it has some drawbacks when used in wireless mesh networks. The new DLEP protocol is supported by the IETF MANET group to fill this gap. In this paper we describe the advantages of a flexible node design for community networks based on the DLEP protocol. In addition, we present our implementation of the DLEP protocol and discuss some important deviations from the current draft version of the standard.

On improving connectivity and network efficiency in a heterogeneous military environment

In this article, we examine some major challenges to be solved in order to provide efficient end-to-end connectivity, resource management and QoS in a tactical military heterogeneous network (including the mobile edge). We briefly describe a selected set of possible solutions and mechanisms to improve inter-domain and intra-domain networking for the tactical heterogeneous network that will be further studied in the NATO STO IST-124/RTG-061 group “Heterogeneous tactical networks - improving connectivity and network efficiency”.

NHDP and OLSRv2 for community networks

The OLSR.org implementation of OLSRv1 (olsrd) is one of the most widely deployed open source mesh routing daemons. The extensive use of olsrd in community networks provided valuable insights leading to the design of OLSRv2 and the development of the OLSR.org network framework (OONF). In this paper, we describe this evolutionary process and our OLSRv2 implementation based on OONF which also supports embedded platforms. In addition, we present some enhanced features unique to our implementation. These features include means to increase the self-configuration capabilities also in mixed setups of IPv4-only, IPv6-only and dual-stack configurations. The implementation process and the protocol evaluation have been supported by the Virtual Confine Testbed, extended by a Rician fading model. This allows for bug identification in the code and for a first but realistic performance comparison between OLSRv1 and OLSRv2 for wireless links. These results will also allow for targeted extensions of OLSRv2 for a better trade-off between the new flexibility of the type-length-value-based packet format RFC5444 and the efficiency of a binary format like the one OLSRv1 uses.

Extending OLSRv2 for tactical applications

In this paper, we present novel approaches to routing in tactical networks. We combine recent advances in OLSR development regarding modularization, scalability, extensibility, and metrics with a node architecture concept based on radio and router separation adopted to tactical networks. This node architecture consists of a single router with several external radios acting as wireless bridges and connecting to the router via standard Ethernet. Furthermore, we propose the use of our Directional Airtime (DAT) routing metric that is suitable for the heterogeneous link characteristics often found in tactical networks. In addition, we present some enhanced features unique to our implementation that include means to increase the self-configuration capabilities in IPv4, IPv6, and dual-stack configurations. For the protocol evaluation we used a physical testbed consisting of over 20 nodes implementing our tactical node design. We propose the use of this architecture in tactical networks in order to improve route selection, increase scalability and simplify network administration.

Advances in wireless community networks with the community-lab testbed

Beyond traditional telecom providers, citizens and organizations pool their own resources and coordinate in order to build local network infrastructures to address the digital divide in many parts of the world. These crowdsourced network infrastructures can be self-organized and shared by a community for the collective benefit of its members. Several of these networks have developed open, free, and neutral agreements, and are governed as a common-pool resource: community networks. These are built using a variety of commodity wireless hardware (e.g., Wi-Fi long-range point-to-point links, Wi-Fi and GSM access points, and mesh networks), sometimes optical fiber links, heterogeneous nodes, routing protocols, and applications. A group of researchers, developers, and community networks developed the Community-Lab testbed, and for the last five years have worked together to overcome obstacles, improve the technologies, tools, and operational models being used, as well as model best practices for more effective and sustainable community networks. This article presents the challenges for experimentation, the testbeds built, results, lessons learned, and the impact of that work to place wireless community networks as one sustainable way toward an Internet accessible to all.

Evaluation of the scalability of OLSRv2 in an emulated realistic military scenario

Emulation environments are an effective approach to experimenting with and evaluating network protocols, algorithms, and components. This paper describes a joint effort by the NATO Science & Technology Organizations IST-124 Research Task Group to evaluate the scalability of OLSRv1 and OLSRv2 in an emulation environment within a military scenario. The scenario includes detailed mobility patterns for a battalion-sized operation, which has been developed by military experts in planning and executing live exercises. The mobility patterns are used to drive the network emulation. The scalability of OLSRv1 and OLSRv2 (with and without MPR) is assessed by emulating different network sizes and estimating the overhead. Moreover, the unicast packet delivery ratio is calculated for the different OLSR configurations. The results show that with the chosen OLSR update rates, only OLSRv2 with MPR mechanism scales up to 96 nodes.

Joint protection of a military formation using heterogeneous sensors in a mobile ad hoc network: Concept and field tests

This paper presents a concept on how a military formation can be jointly protected by linking available single-platform protection systems. To achieve this, a mobile ad hoc network is established between different vehicles carrying heterogeneous sensors, specifically acoustic and ESM sensors, emulating the protection systems. Distributed data fusion is applied to provide a situation overview for localizing a threat. To substantiate the concept, results from field tests regarding network, sensor, and data fusion functionality are presented.

Middleware for coordinating a tactical router with SOA services

In this paper, we introduce an architectural concept for the adaption of SOA-technology (in particular Web services) in order to enable operational use in the tactical domain (typically featuring low-bandwidth communication links with high delays and frequent disruptions). For this purpose, an Enterprise Service Bus specially tailored for the tactical domain (a “tactical ESB”) is used as a technical infrastructure for the SOA. On the network side, a “tactical router” provides connections to different radio technologies (e.g. VHF, HF based radios, satellite communication, etc.). A specially tailored cross-layer middleware is introduced to coordinate ESB (infrastructure) services with the tactical router. The middleware uses a specific state exchange mechanism in order to increase the efficiency of the overall system. Therefore, it obtains characteristics of the network environment and takes advantage of them in order to improve the quality of data transfers. In addition, a prototypical implementation of the architectural concept is briefly described. There, the designed components and interfaces were prototypically implemented and coupled with RuDi (an Apache CXF - based ESB by IABG [4]) and an in-house developed prototype of a tactical router.