Inter-Domain Routing and Data Replication in Virtual Coordinate Based Networks

In recent work it has been shown that the use of virtual coordinates or identifiers for efficient routing and data management has several advantages compared to the use of predefined addresses or geographical coordinates. However, these advantages only hold for single domain networks with limited mobility. In this paper, we discuss the challenges arising from using virtual coordinates for routing (to a particular sensor ID or to indexed data or resources) in ad hoc and sensor networks in multi-domain network scenarios. We show the feasibility of inter-domain routing by exploiting a concept that is central to most virtual coordinate approaches: the availability of data management operation using a DHT like mechanism. Based on the Virtual Cord Protocol (VCP), we show how inter-domain routing can be realized using appropriate indirections. Furthermore, we investigate the possibility of replicating data among different networks, or DHTs, to provide seamless data access in multi-domain environments. Our simulation results clearly show that both functions can be realized with only marginal overhead.

I. Introduction

Routing in sensor network scenarios is still a challenging issue, especially taking into account the unreliability of nodes and links, the geographical spreading of the networks, and the need to completely self-organize all routing functions. The main objective is usually to access produced sensor data in a seamless manner, independent of the current topology [1]. Routing in sensor networks is dominated by two basic approaches: either based on conventional, routing table driven Mobile Ad Hoc Network (MANET) solutions or by content based routing, where the route is discovered step by step from content we are looking for. The most common example is geo-routing, where the content is represented by geographic coordinates of the destination. In this case, all nodes have geographic position identifiers (learned from GPS for example). For most scenarios, MANET based routing turned out to be less scalable due to routing table storage overhead as well as traffic update overhead to adjust to topology changes. The traffic overhead is due to periodic updates in proactive routing schemes or to flood search in reactive schemes. Position-based routing solutions inherently improve the situation as simple greedy routing towards the destination can be employed. However, such approaches only work well if the network is dense, as routing holes cause geographic routing to rely on inefficient face routing methods. Additionally, GPS is required for all the nodes have to be able to precisely obtain their geographic locations, and a Geo Location Service (GLS) is necessary to find the destination coordinates [2].