5. RPL Instance

Within a given LLN, there may be multiple, logically independent RPL Instances. A RPL node may belong to multiple RPL Instances, and it may act as a router in some and as a leaf in others. This document describes how a single instance behaves.

There are two types of RPL Instances: Local and Global. RPL divides the RPLInstanceID space between Global and Local instances to allow for both coordinated and unilateral allocation of RPLInstanceIDs. Global RPL Instances are coordinated, have one or more DODAGs, and are typically long-lived. Local RPL Instances are always a single DODAG whose singular root owns the corresponding DODAGID and allocates the local RPLInstanceID in a unilateral manner. Local RPL Instances can be used, for example, for constructing DODAGs in support of a future on-demand routing solution. The mode of operation of Local RPL Instances is out of scope for this specification and may be described in other companion specifications.

The definition and provisioning of RPL Instances are out of scope for this specification. Guidelines may be application and implementation specific, and they are expected to be elaborated in future companion specifications. Those operations are expected to be such that data packets coming from the outside of the RPL network can unambiguously be associated to at least one RPL Instance and be safely routed over any instance that would match the packet.

Control and data packets within RPL network are tagged to unambiguously identify of which RPL Instance they are a part.

Every RPL control message has a RPLInstanceID field. Some RPL control messages, when referring to a local RPLInstanceID as defined below, may also include a DODAGID.

Data packets that flow within the RPL network expose the RPLInstanceID as part of the RPL Packet Information that RPL requires, as further described in Section 11.2. For data packets coming from outside the RPL network, the ingress router determines the RPLInstanceID and places it into the resulting packet that it injects into the RPL network.