A computer network consists of computers that communicate via any physical media through a network formed by links and nodes, the nodes being the computers. Computer networks have evolved along their short history. Computer networks have changed drastically in mission and implementation from the early projects supported by the Advanced Research Projects Agency (ARPA) and from other organizations, tracing back the origins to 1962. The ARPA network (ARPANET) consisted initially of a small set of nodes at research centres and universities, connected with links at 56 kbps across the United States. ARPANET was the core of the early Internet, a network for research centres and universities. Computer networks are based on the concept of packet switching within a shared communication medium, as opposite to circuit switching, the dominant paradigm for the precedent telegraph and telephone networks. In 1968 Paul Baran proposed a network system based on nodes that forward datagrams or packets from different users over a common line between computer systems from origin to destination. The packet switching paradigm provides resiliency of network against network node failures, the independent routing of datagrams per node makes possible that the datagrams reach their destination even in presence of multiple node failures.
Key Terms in this Chapter
Grid: Grid problem is defined as flexible, secure, coordinated resource sharing among dynamic collections of individuals, institutions, and resources referred to as virtual organizations. In such settings, unique authentication, authorization, resource access, resource discovery, and other challenges are encountered
Routing: Routing is the process of selection of path for the packets in a computer network. Normally it is performed using dynamic routing tables that change with network topology, or statically configured in small networks.
Routing Protocols: Protocols used by network nodes (routers) to perform routing. The information interchanged by the nodes to obtain the routing tables is identified as the control plane and the traffic packets forwarded is the user plane.
Wireless Mesh Networks: Wireless mesh networks (WMNs) consist of mesh routers and mesh clients, where mesh routers have minimal mobility and form the backbone of WMNs. They provide network access for both mesh and conventional clients. (Akyildiz, Wang, & Wang, 2005)
Packet Switching: Each packet is routed independently at each node and sent to next node through communication links shared by other nodes. It is opposite to circuit switching, where resources of the network are reserved between origin and destination prior to the communication and released at the end.
Grid Technologies: Grid technologies address It is this class of problem that is addressed by Grid technologies. Next, the authors present an extensible and open Grid architecture, in which protocols, services, application programming interfaces, and software development kits are categorized according to their roles in enabling resource sharing.
Overlay Network: A computer network built using a subset of the nodes on top of another network. Links in the overlay network may be formed by several logical links in the network below. Many peer-to-peer applications are overlay networks.
Middleware: Describes the software used to interconnect software applications. Middleware allows building complex distributed applications to support virtual organizations. Examples of middleware are application servers and Web servers.
Ad Hoc Networks (MANETs): Self-organising, self healing, mobile wireless network that does not rely on infrastructure in which mobile nodes are responsible for discovery of each other and subsequent cooperation so that communication is possible.
Communications Protocols: The set of standard rules for data representation, signalling, authentication, and error detection required to send information over a communications channel (Wikipedia, 2006).
Peer-to-Peer Applications (P2P): A P2P is a network established between autonomous and cooperating nodes that self organize on a peer basis sharing resources of nodes, rather than centralized servers operating on a client-server basis. The peer-to-peer model is the standard at Internet for many protocols and telephone communications; the best-known applications are Freenet, eMule, Skype.