A grid, as described by the Open Grid Service Network (OGSA) is “a system that is concerned with the integration, virtualization, management of service and resources in a distributed heterogeneous environment that supports collection of users and resources (virtual organization) across traditional administrative and organisational domains.” . Virtual organizations are set of individuals or organisations having access to the computers, software, data and other resources for collaboration or other purposes. VO provides a mechanism for associating users their requests and a set of resources. In a grid topology each node can send or receive data to other nodes or share resources with any other node via inter connected links, irrespective of their physical locations. Grid network provides a path to migrate from
cluster networks to a truly distributed and integrated applications. The data travel in multi- hops, through multiple links and nodes. A conceptual view of the grid network is shown in
Fig: 1.
Fig 1: Conceptual View Of Optical Grid Network
Grid network has the potential in executing resource efficient network services with high data rates between geographically widely distributed users. In context to high data rates, optical network comes out as a major potential for the grid. Wavelength division multiplexing (WDM) has emerged as an attractive core transmission technology for future wide-area backbone networks. It provides enormous bandwidth at the physical layer for applications. All-optical networks can be achieved by using devices such as optical cross connects (OXC).Optical network uses lightpaths to transfer data. A lightpath is an all-optical end-end communication between nodes or users. It’s a wavelength continuous physical route. Same wavelength is used in all the links and connecting nodes of the path.
Grid Applications
Optical Grids offers various potential applications. In today’s Internet we have a very rich set of application types. These applications can possibly be categorized as follows:
• High Energy Particle Physics
• Very Long Baseline Interferometry
• High Performance Computing and Visualisation
• eHealth applications: proof-of-concept of remote screening
• Logistical Networking
• Grid applications contributing large (or increasing) number of anonymous users
Optical Grid Network Architecture
It consists of 3 layers: an application layer, optical-grid control layer and optical network control layer. There are two
interfaces: application-to-optical-grid interface (AGI) and optical-grid-to-network interface (GNI). The users request for jobs to the network through a Grid User Network Interface (GUNI) along with the characteristics and requirements of the jobs. The application layer requests a set of lightpaths through the AGI. The optical-grid control layer that continuously collects information on network resources and availability from the optical network layer via the GNI, likewise announces their capabilities (storage space, processing power, etc.).
The optical-grid control layer which develops specific topological information separates the request into multiple lightpath requests. Then it sends requests for the establishment of each lightpath to the optical-network layer via the GNI. After the lightpaths are established by the optical-network control layer, notification of the successful requests is sent to the optical- grid control layer, which then also notifies the application layer. After that, the application begins sending the data to the destination end node via the D-plane of the optical network. The network topology, bandwidth and other characteristics will need to be known to the Grid scheduling and/or routing algorithm.
References : IEEE, Wikipedia
