Many major grid projects are being built using the Globus Toolkit: grid software being developed by the Globus Alliance, a team primarily involving Ian Foster's team at Argonne National Laboratory and Carl Kesselman's team at the University of Southern California in Los Angeles.

The Globus Toolkit is a set of software tools required to construct a grid. These tools cover security measures, resource location, resource management, communications and so on.

Many of the protocols and functions defined by the Globus Toolkit are similar to those in networking and storage today, but have been optimized for grid-specific deployments.

Globus includes programs such as:

• GRAM (Globus Resource Allocation Manager): figures out how to convert a request for resources into commands that local computers can understand
• GSI (Grid Security Infrastructure): authenticates users and determines their access rights
• MDS (Monitoring and Discovery Service): collects information about resources such as processing capacity, bandwidth capacity, type of storage, and so on
• GRIS (Grid Resource Information Service): queries resources for their current configuration, capabilities, and status
• GIIS (Grid Index Information Service): coordinates arbitrary GRIS services
• GridFTP (Grid File Transfer Protocol): provides a high-performance, secure, and robust data transfer mechanism
• Replica Catalog: provides the location of replicas of a given dataset on the Grid
• The Replica Management system: manages the Replica Catalog and GridFTP, allowing applications to create and manage replicas of large datasets.

There are two main reasons for the strength and popularity of the Globus toolkit:

1. Grids need to support a wide variety of applications created according to different programming paradigms. Rather than providing a uniform programming model for grid applications, the Globus Toolkit has an "object-oriented approach", providing a bag of services so that developers can choose the services that best meet their needs. The tools can also be introduced one at a time. For example, an application can use GRAM or GRIS without having to necessarily use the Globus security or replica management systems.
2. The Globus Toolkit is available under an "open-source" licensing agreement, which means anyone is free to use or improve the software. This is similar to the World Wide Web and the Linux operating system.