ADHOC NETWORKS

A wireless ad-hoc network is a decentralized type of wireless network. The network is ad hoc because it does not rely on a preexisting infrastructure, such as routers in wired networks or access points in managed (infrastructure) wireless networks. Instead, each node participates in routing by forwarding data for other nodes, and so the determination of which nodes forward data is made dynamically based on the network connectivity. In addition to the classic routing, ad hoc networks can use flooding for forwarding the data.
An ad hoc network typically refers to any set of networks where all devices have equal status on a network and are free to associate with any other ad hoc network devices in link range. Very often, ad hoc network refers to a mode of operation of IEEE 802.11 wireless networks.

It also refers to a network device's ability to maintain link status information for any number of devices in a 1 link (aka "hop") range, and thus this is most often a Layer 2 activity. Because this is only a Layer 2 activity, ad hoc networks alone may not support a routable IP network environment without additional Layer 2 or Layer 3 capabilities.

The earliest wireless ad-hoc networks were the "packet radio" networks (PRNETs) from the 1970s, sponsored by DARPA after the ALOHA net project. On wireless computer networks, ad-hoc mode is a method for wireless devices to directly communicate with each other. Operating in ad-hoc mode allows all wireless devices within range of each other to discover and communicate in peer-to-peer fashion without involving central access points (including those built in to broadband wireless routers).

To set up an ad-hoc wireless network, each wireless adapter must be configured for ad-hoc mode versus the alternative infrastructure mode. In addition, all wireless adapters on the ad-hoc network must use the same SSID and the same channel number.
An ad-hoc network tends to feature a small group of devices all in very close proximity to each other. Performance suffers as the number of devices grows, and a large ad-hoc network quickly becomes difficult to manage. Ad-hoc networks cannot bridge to wired LANs or to the Internet without installing a special-purpose gateway.

Ad hoc networks make sense when needing to build a small, all-wireless LAN quickly and spend the minimum amount of money on equipment. Ad hoc networks also work well as a temporary fallback mechanism if normally-available infrastructure mode gear (access points or routers) stop functioning.

COMPUTER NETWORKS

          A computer network, often simply referred to as a network, is a collection of hardware components and computers interconnected by communication channels that allow sharing of resources and information. Where at least one process in one device is able to send/receive data to/from at least one process residing in a remote device, then the two devices are said to be in a network.

           Networks may be classified according to a wide variety of characteristics such as the medium used to transport the data, communications protocol used, scale, topology, and organizational scope.

Communications protocols define the rules and data formats for exchanging information in a computer network, and provide the basis for network programming. Well-known communications protocols are Ethernet, hardware and Link Layer standard that is ubiquitous in local area networks, and the Internet Protocol Suite, which defines a set of protocols for internetworking, i.e. for data communication between multiple networks, as well as host-to-host data transfer, and application-specific data transmission formats.

Computer networking is sometimes considered a sub-discipline of electrical engineering, telecommunications, computer science, information technology or computer engineering, since it relies upon the theoretical and practical application of these disciplines

             Some form of network software is required. This network protocol software is installed through the network preferences. NetBIOS was commonly used though recently a secure TCP/IP protocol has been developed. The network protocol determines how computers become part of the network and how they are recognized. The network must have a name and you can use some creativity at this point. Each computer must also have a unique name that other computers on the network can access them with.

If all goes well this is all you need but often there will be a conflict that can be resolved by establishing exactly how the computer will communicate. To solve these types of conflict your network needs a set DNS server address and each computer in the network needs to be assigned a unique IP address

                 A computer with an Internet connection can also share that connection with other computers on the network but you should check with your ISP what their policy on sharing Internet connections is. Sharing an Internet connection also raises some serious security issues. Many cable high speed Internet connections use the Network Neighborhood settings to create the Internet connection and connecting your home or office network to this existing system can cause problems

Routing:

                  Routing is the process of moving data from one network to another by forwarding packets via gateways. With IP based networks, the routing decision is based on the destination address in the IP packet's header. Routing also occurs in networks running other protocols, which are not discussed here. It is the process of learning all the paths through the network (routes) and using routes to forward data from one network to another. A protocol is a standardized way to perform a task. So, a routing protocol would be a standardized way of learning routes and moving data from one network to another. 

Routing protocols:

                 A routing protocol is a standardized process by which routers learn and communicate connectivity information, called routes, each of which which describes how to reach a destination host and network. Routers that wish to exchange routing information must use the same routing protocol to communicate routing information. Routing protocols are used by routers to dynamically learn all paths through a set of networks and forward data between the networks. Routers are specialized computer devices designed to perform routing.