The following is a list of common terms used throughout this document.

• Site.  A site is a physical location where PlanetLab nodes are located (e.g. Fraunhofer or UCL). Abbreviated versions of site names prefix all slice names.

• Node.  A node is a dedicated server that runs components of PlanetLab services.

• Slice.  A slice is a set of allocated resources distributed across PlanetLab. To most users, a slice means UNIX shell access to a number of PlanetLab nodes. Slices are assigned to some number of PlanetLab nodes. Principal Investigators (PIs) are responsible for creating slices and assigning them to their users. After being assigned to a slice, a user may then assign nodes to it. After nodes have been assigned to a slice, virtual servers for that slice are created on each of the assigned nodes. Slices have a finite lifetime and must be periodically renewed to remain valid.

• Sliver.  A sliver is a slice running on a specific node. It is a set of allocated resources on a single PlanetLab node.

• Virtual Server (VServer).  Slivers are currently implemented as Linux-Vservers, which implements both namespace and performance isolation among slivers on a single machine. Network virtualization of slivers is implemented using VNET. You may hear the terms slice, sliver, and VServer occasionally interchanged, but there are architectural distinctions between them.

• Principal Investigator (PI).  The Principal Investigator is responsible for managing slices and users at each site. PIs are legally responsible for the behavior of the slices that they create. Most sites have only one PI (typically a faculty member at an educational institution or a project manager at a commercial institution). Be sure that they read the Principal Investigator Guide which describes their roles and responsibilities.

• Technical Contact (Tech Contact).  Each site is required to have at least one Technical Contact who is responsible for installation, maintenance, and monitoring of the site's nodes. The Tech Contact is the person we should contact when a node goes down or when an incident occurs. This is commonly a system administrator or graduate student. Be sure that they read the Technical Contact's Guide which describes their roles and responsibilities.

• User.  A user is anyone who develops and deploys applications on PlanetLab. PIs and Tech Contacts may also be users.

• Administrative Contact.  Each site is required to have an Administrative Contact who is responsible to handle contracts, invoices, etc.

• Authorized Official.  Each site is required to have a person who can bind the institution contractually/legally. It is often a provost or contracting officer. Even though academic and non-profit institutions do not pay a membership fee, we still require the signature of an authorized official.

Note that these roles do not have to be distinct people. For example, it is not uncommon for the Principal Investigator to be the same person as the Technical Contact.