Bow-Nan Cheng

Orthogonal rendezvous routing protocol for wireless mesh networks

Routing in multi-hop wireless networks involves the indirection from a persistent name (or ID) to a locator. Concepts such as coordinate space embedding help reduce the number and dynamism complexity of bindings and state needed for this indirection. Routing protocols which do not use such concepts often tend to flood packets during route discovery or dissemination, and hence have limited scalability. In this paper, we introduce Orthogonal Rendezvous Routing Protocol (ORRP) for meshed wireless networks. ORRP is a lightweight-but-scalable routing protocol utilizing directional communications (such as directional antennas or free-space-optical transceivers) to relax information requirements such as coordinate space embedding and node localization. The ORRP source and ORRP destination send route discovery and route dissemination packets respectively in locally-chosen orthogonal directions. Connectivity happens when these paths intersect (i.e., rendezvous). We show that ORRP achieves connectivity with high probability even in sparse networks with voids. ORRP scales well without imposing DHT-like graph structures (eg: trees, rings, torus etc). The total state information required is O(N3/2 for N-node networks, and the state is uniformly distributed. ORRP does not resort to flooding either in route discovery or dissemination. The price paid by ORRP is suboptimality in terms of path stretch compared to the shortest path; however we characterize the average penalty and find that it is not severe.

A comparison of MANET routing protocols on airborne tactical networks

In highly dynamic airborne networks, multi-hop routing becomes increasingly difficult due to high mobility, intermittent links and link quality, and the need to scale. Traditionally, airborne tactical networks have leveraged existing MANET proactive, reactive, and hybrid routing protocols with modifications for cross-layer information, to provide multihop routing. Although there has been some success with utilizing these protocols individually in airborne networks, a proper comparison of all types of MANET routing protocols at scale, with mobility patterns associated with airborne tactical networks, is lacking. In this paper, we compare a variety of proactive and reactive MANET routing protocols such as AODV, OLSR and OSPF-MDR, under relative node velocities and mobility patterns associated with airborne networks. Specifically, we evaluate each protocol in terms of routing overhead traffic, end-to-end message completion rate, and end-to-end delay, to examine performance vs. tradeoff.

Characterizing routing with radio-to-router information in an airborne network

The current generation of long-range, high capacity, military radios are stove-piped systems that work well in a homogeneous environment, but require significant setup and configuration to interoperate with other radio systems. Each radio provides a subset of disparate link information in nonstandard interfaces and has built-in home-grown or industry-based routers running potentially different routing protocols. In a heterogeneous radio system airborne environment, wireless link characteristics change rapidly, often requiring direct link feedback from the radio to make routing decisions. In recent years, there has been a number of work in developing a common radio-to-router interface that standardizes a subset of per-link information to pass to the network layer for use in dynamic MANET routing. While simulations and emulation tests can provide a baseline for how systems will perform, field-tests are crucial to demonstrate capabilities in real-world operating environments. In this paper, we present measurement results from a field test involving three airborne and two ground assets with various radio systems that test an implementation of RFC4938, a radio-to-router interface protocol, and its interaction with a modified OSPFv3 routing protocol to support dynamic link metrics and OSPF cost generation. The assets participated in the exercise formed a high capacity, dynamically routed aerial IP backbone made of heterogeneous radio technologies over 250 nautical miles (Nm), allowing the passing of military operational traffic.1

Evaluation of a Multihop Airborne IP Backbone with Heterogeneous Radio Technologies

In recent years, there has been increasing interest in the US Department of Defense to build an on-demand airborne network for communications relay utilizing high-capacity, long-range military radio systems. While these systems operate well in a network of homogeneous systems, platforms generally employ multiple heterogeneous radio systems making internetworking difficult due to varying radio characteristics and lack of interoperability. Although simulations and emulation tests can provide a baseline for how systems will perform in a controlled environment, field tests are crucial to demonstrate capabilities in real-world operating environments. In this paper, we present measurement results from a field test involving two airborne platforms forming a dynamically routed aerial IP backbone over 200 nautical miles with various radio systems as part of the C4ISR on-the-move 2010 exercise. We present measurement results on per link performance, radio-to-router interface performance, and multihop network performance results with prototype software on open source platforms. Additionally, key lessons learned and recommendations are given.

Radio-to-router interface technology and its applicability on the tactical edge

Tactical wireless and mobile networks are the primary networking infrastructure in the Global Information Grid (GIG) to provide end-to-end connectivity to the warfighters at the tactical edge. The highly dynamic nature of tactical edge networks raise a number of challenging issues related to data transport and service delivery in the tactical environment. To address some of these issues, DoD waveforms have increasingly leveraged layer 2 link information to make smart cross-layer multihop routing decisions. Although there has been some measure of success in providing higher end-to-end data delivery, the lack of standard interfaces between the radio and router have led to interoperability issues in environments with a heterogeneous mix of radio systems. As a result, there has been increased desire to standardize radio-to-router interfaces (R2RIs) as a means to separate radio and router functionality and to allow greater interoperability between systems. In this article, we examine three R2RI protocols currently being vetted through the Internet Engineering Task Force and currently integrated or under consideration in DoD radio systems (RFC 5578, R2CP, and DLEP), and identify their current use and applicability in the tactical edge. Furthermore, we identify some challenges in implementing any R2RI scheme into emerging systems.

Design considerations for next-generation airborne tactical networks

Airborne tactical networks (ATNs) have provided protected air-to-air communications for military aircraft for several decades. To support emerging and future warfighter needs, the next generation of systems will require significant improvements to provide higher capacity, longer range, greater flexibility, and increased interoperability. Governed by domain characteristics such as long transmission ranges, low-to-medium data rates, latency constraints, and link protection needs, the air tactical domain poses several unique requirements on link and network design. Developing next-generation ATNs requires an understanding of the airborne tactical domain, including the design constraints and challenges at various layers of the network stack. In this article, we provide an overview of the unique domain characteristics of ATNs and highlight the key design challenges and research areas associated with the physical, link, and network layers.

An implementation of a Common Virtual Multipoint Interface in Linux

In highly dynamic airborne environments, per link information becomes crucial in effectively routing packets throughout the network. Point-to-point Protocol over Ethernet (PPPoE) RFC4938/55781 describes an elegant way to standardize an interface to transmit per link information to the router to make educated routing decisions. These dynamically changing point-to-point links to the router pose an interesting challenge in defining interfaces in the router configuration and providing multicast/broadcast emulation. In this paper, we present an open-source, Linux implementation of a Common Virtual Multipoint Interface (CVMI). The CVMI aggregates multiple point-to-point interfaces into a virtual interface and provides multicast/broadcast emulation on these dynamically changing interfaces. We describe our implementation in detail and show how each link can be grouped to perform differently despite the homogeneous nature of PPP links and provide some basic performance evaluations to show functionality. 2

Internet protocol header compression technology and its applicability on the tactical edge

The increased usage of net-centric IP applications at the tactical edge has pushed DoD communications systems to maximize bandwidth efficiency amid a limited availability of RF spectrum. One method of increasing bandwidth efficiency (especially with the desire to move to IPv6), is the use of IP header compression (IPHC) to compress headers from the network layer and above into small identifiers before sending to the link layer. Although widely used in cell phone technology, the tactical edge provides some unique challenges to traditional IPHC techniques including highly dynamic links and link conditions due to potential jamming threats and difficult environments, multi-hop scenarios due to lack of infrastructure, and a highly diverse set of radio systems lacking interoperability. In this article, we examine two common IP header compression schemes, Robust Header Compression (RFC 5225) and IP Header Compression (RFC 2507) and one experimental scheme, MANET IP header compression, and identify their current use and applicability in the tactical edge. Furthermore, we identify some challenges in implementing header compression schemes in emerging systems.

Evaluation of a multi-hop airborne ip backbone with heterogeneous radio technologies

In recent years, there has been increasing interest in the US Department of Defense to build an on-demand airborne network for communications relay utilizing high-capacity, long-range military radio systems. While these systems operate well in a network of homogeneous systems, platforms generally employ multiple heterogeneous radio systems making internetworking difficult due to varying radio characteristics and lack of interoperability. Although simulations and emulation tests can provide a baseline for how systems will perform in a controlled environment, field tests are crucial to demonstrate capabilities in real-world operating environments. In this paper, we present measurement results from a field test involving two airborne platforms forming a dynamically routed aerial IP backbone over 200 nautical miles with various radio systems as part of the C4ISR on-the-move 2010 exercise. We present measurement results on per link performance, radio-to-router interface performance, and multihop network performance results with prototype software on open source platforms. Additionally, key lessons learned and recommendations are given.

Comparing radio-to-router interface implementations on experimental CoTs and open source routers

In highly dynamic wireless environments, link metrics such as link quality, availability, and others have become increasingly important to enable smart multi-hop routing decisions. In recent years, a number of radio-to-router interface (R2RI) protocols such as Point-to-Point over Ethernet RFC5578, Dynamic Link Exchange Protocol (DLEP), and Radio-Router Control Protocol (R2CP) have emerged to address the need to have a common set of link metrics exposed from the radio to the router to enhance multi-hop routing decisions. To fully evaluate R2RI functionality and specifications, differing implementations of both radio/client and router/server-side R2RI protocols must be prototyped and tested. In this paper, we present comparison tests of each of the three (3) radio-to-router interfaces with two (2) router/server-side R2RI experimental/beta R2RI implementations: one on a commercial Cisco router, and one on an open source Quagga platform. The goal of the comparison is not necessarily to provide a holistic performance comparison (as much of the code is experimental), but to highlight implementation differences and potential issues. In many cases, issues are already resolved in future releases.1