1 Introduction

Wireless networks are increasingly popular because of technological improvements. As wireless devices become more portable, wireless networks may be set up in places where it is not suitable to set up an infrastructure. Wireless networks without infrastructure are called ad-hoc networks. Uses include disaster recovery, law enforcement, military and collaborative.

Routing protocols for wired networks do not necessarily work in ad-hoc wireless networks, because of rapidly changing topology, unreliable links and lack of structure.

Many routing protocols for ad-hoc wireless networks exist, where nodes forward traffic for each other. However, few of them have been conceived with a large network in mind. Therefore, we will look into the scalability of ad-hoc wireless networks.

Instead of examining all protocols one-by-one, we will look into protocol classes and explain a few protocols in detail. We will show that only Hazy Sighted Link State protocol is simple to set up and scales well.

In section 2, we will discuss proactive routing protocols, which keep active routing information. In section 3 on-demand protocols are described, which only seek a routing path when needed. Hierarchical routing protocols, which divide the network in clusters, are discussed in section 4. Geographical protocols are reviewed in section 5. Finally, section 7 concludes.