Architecting and designing : UML 2.0 Lite : UML models : UML Deployment diagram : Node
  
Node
A node is a run-time physical object that represents a computational resource, generally having memory and processing capability. You can model node types and node instances.
You may model the component instances that run or live on a node by drawing them within the node. You may model which nodes communicate with one another using the Connection relationship line.
See also
UML Deployment diagram