81 Copyright © 2012, IGI Global. Copying or distributing in print or electronic forms without written permission of IGI Global is prohibited. Chapter 5 DOI: 10.4018/978-1-4666-0321-9.ch005 INTRODUCTION Mobile ad hoc network (MANET) is formed by a group of nodes that communicate with each other over a single or multiple wireless channels. They operated in a decentralized and self–organizing manner without the necessity for a fixed wireless networking infrastructure. An outstanding feature of MANET is the multihop mode of communica- tions, beyond the direct radio connection amongst the nodes. Each node could be a transmitter, a receiver or a router forwarding data traffic toward its destination. The fundamental idea of such networks goes back to the 1980s (I. Chlamtac, M. Conti, and J. J.-N. Liu (2003)), but have shown an increase in research interest recently, due to emerging technology in wireless communica- tions and the microelectronic industries. A node is typically equipped with a radio transmitter and receiver, which allows communication sessions Jiwa Abdullah Universiti Tun Hussein Onn Malaysia, Malaysia Connectivity as a Fundamental Characteristic of Mobile Ad Hoc Networks ABSTRACT In this chapter, the idea of formulating the node connectivity into a form suitable for the purpose of monitoring the dynamic of any given node pair was proposed. It had been able to show that the node connectivity time constitutes the length of time where node-pairs are connected and communication ses- sions can be established. By analytical calculation and simulation, the node connectivity time depends on the relative velocity of the node-pair. It shows that there is an upper limit and a lower limit for the connection time. Between these limits, communication sessions can be carried out. In order to monitor the quality of connection between a node-pair and for the whole route which is made up of a collection of node-pairs, npem, npcm, and nci are introduced. The nci is shown to be a viable way to estimate the quality of node-pair connection in terms of its timeliness. The index, nci, could be used as one of the metrics to identify and select the best path to the destination.