1.3.3 Clouds

A PNRP node can participate in one or more clouds. A cloud is a group of nodes that can communicate with each other to resolve names into addresses. Each node maintains a cache of PNRP ID-to-endpoint mappings (called route entries). A node is required to cache its Leaf Set (the five PNRP IDs on each side that are numerically closest to each of the node's own PNRP IDs), plus any others it knows of. Messages are exchanged between nodes to distribute information about PNRP IDs. For purposes of determining numerical closeness, the PNRP ID numbering space is considered to be circular (for example, 2^256-1 is adjacent to 0 in a numbering space of size 2^256).

A cloud has a scope property that can be Global, Site Local, or Link Local, as illustrated by the following diagram. A node can be connected to the Global cloud, multiple Site Local cloud, and multiple Link Local clouds. Communication between nodes never crosses from one cloud to another.

Node scoping (Link Local, Site Local, Global)

Figure 3: Node scoping (Link Local, Site Local, Global)

Participation in clouds involves a number of distinct tasks:

  • Cloud discovery

  • Joining the cloud

  • Active participation in the cloud

  • Leaving a cloud