Mesh Networks
Meshworks are networks of devices which connect to each other without prior infrastructure. They are also called viral communicators.
Introduction
From a summary in Technology Review:
"Meshies believe that mesh networks will overthrow traditional networking and communications and create entirely new kinds of distributed software. For the purposes of this column, mesh networks (sometimes called mobile ad hoc networks, or MANETs) are local-area networks whose nodes communicate directly with each other through wireless connections. It is the lack of a hub-and-spoke structure that distinguishes a mesh network. Meshes do not need designated routers: instead, nodes serve as routers for each other. Thus, data packets are forwarded from node to node in a process that network technologists term "hopping."
Before dismissing mesh networks as being of interest only to specialists, consider their advantages over existing hub-and-spoke networks. Mesh networks are self-healing: if any node fails, another will take its place. They are anonymous: nodes can come and go as they will. They are pervasive: a mobile node rarely encounters dead spots, because other nodes route around objects that hinder communication. Meshes are cheap, efficient, and simple. But they are still in development. The chief technical challenge for meshes is the inherent unreliability of wireless links. Because the unreliability compounds with each hop, the size of meshes is now limited. A related problem with hopping is that, for now, moving nodes seldom establish new connections "seamlessly": when a network's topology changes, some transmission paths can be temporarily disrupted. Therefore, voice and video sit unhappily on meshes. Meshes lack standards, too: low-bit-rate mesh networking has a standard called ZigBee that is supported by around 100 companies, including Motorola, Mitsubishi, Phillips, and Samsung, but high-bit-rate communications have no such standard (although the 802.11 committee of the Institute of Electrical and Electronics Engineers hopes to create one by next May).
What does all this mean? A few, early applications of mesh networks are already emerging. Meshes will allow municipalities to create cheap or free urban Wi-Fi networks (we will be writing about Philadelphia's effort in our November issue). Meshes have obvious advantages for military and security personnel who want networks that are unbreakable and "horizontal" (see "Instant Networks," June 2005). Environmental scientists like meshes because they can provide continuous data from large geographical areas over many years (see "Casting the Wireless Sensor Net," July/August 2003). But the most important application of meshes will be in what technologists once called "pervasive computing": embedding sensors and processors in things like clothes, electronics, and buildings and connecting them into smart networks.
But I believe that the most intriguing aspect of mesh networks is their cybernetic qualities. That is, mesh networks are adaptive systems that resemble biological systems (we recently wrote about MIT mathematics professor Norbert Wiener, the founder of cybernetics: see "Cybernought," June 2005). Many meshies like to say that they draw their inspiration from the behavior of swarming bees or ants." (http://www.technologyreview.com/articles/05/09/issue/editor.asp?trk=nl)
Applicatons
Mesh Networks or Ad Hoc Networks for the telecom sector, as described in The Economist:
"The mesh-networking approach, which is being pursued by several firms, does this in a particularly clever way. First, the neighbourhood is “seeded" by the installation of a “neighbourhood access point" (NAP)—a radio base-station connected to the Internet via a high-speed connection. Homes and offices within range of this NAP install antennas of their own, enabling them to access the Internet at high speed.Then comes the clever part. Each of those homes and offices can also act as a relay for other homes and offices beyond the range of the original NAP. As the mesh grows, each node communicates only with its neighbours, which pass Internet traffic back and forth from the NAP. It is thus possible to cover a large area quickly and cheaply." (http://www.economist.com/printedition/displayStory.cfm?Story_ID=1176136
Discussion
Meshworks are different from P2P Networks
As far as I understand the distinction, P2P works on the existing infrastructure, which may or not be P2P itself, while meshworks create a new infrastructure which is much more thoroughly distributed.
From a discussion of a Technology Review article at http://www.technologyreview.com/Infotech/18284/page1/
"In a P2P network, the physical infrastructure still looks like a tree, but the bandwidth is more efficiently employed because underutilized branches can become content distributors as well as receivers. A P2P network does not increase the total bandwidth available, it just uses the bandwidth better.
In a mesh network, users form new infrastructure by connecting directly (and often through multiple alternate pathes), and the network no longer looks like a tree. A mesh network increases the system's total bandwidth.
Both P2P and mesh networks benefit from "network effects" (i.e., the more users, the better the network), and they are complementary approaches. However, mesh networks have a number of benefits that P2P networks do not, including increasing the resiliency of the network and reducing the control that any ISP can exert over the content distributed on the network and the cost of connection."
More Information
See the Wikipedia article, at http://en.wikipedia.org/wiki/Mesh_networks