Technical Specs

• RFC 6719: The Minimum Rank with Hysteresis Objective Function
RPL does the following:
• Offers a number of advanced features, such as trickle timers limiting the chattiness of the control plane, dynamic link (hop count,
throughput, latency, link/path reliability (ETX), link colors), and node routing metrics (node state/attribute, node power levels)
for constraint-based routing useful for combined AMI (Advanced Metering Infrastructure) and DA (Distributed Automation)
deployments.
• Supports multi-topology routing with the support of multiple Directed Acyclic Graphs (DAGs) where each DAG is optimized
against different constraints and metrics dictated by the objective function.
• Reduces the probability of loops occurring as well as detects these loops by employing data path validation, and then breaking
the loops using local poisoning.
• CGR and RME implementations support a non-storing mode for RPL.
• Supports both local repair (faster and sub-optimal) and global re-optimization.
• RPL constructs the routing tree of the meters.
Each node builds and maintains up to three Destination-Oriented Directed Acyclic Graphs (DODAG) parents that provide a path to
the Root CGR.
RMEs implement a non-storing mode because the expected traffic flow for AMI applications primarily flows through the CGR.
Implementing non-storing mode helps save memory on RMEs by only storing the DODAG parents and the neighbors on the sub-DAG.
In non-storing mode, each node maintains their DODAG parents and uses them as default routes. The routing graph, created by the
set of DODAG parents across all nodes, defines the set of upward routes—each node reports their DODAG parents to the CGR so
that the router can generate source routes when delivering datagrams across the PAN. Likewise, nodes establish downward routes
by advertising their parent set towards the DODAG Root. Because RMEs implement the non-storing mode of RPL, nodes report
their parent sets directly to the Root; and, the Root must store the information. The Root uses this information when determining
source routes needed for delivering datagrams to individual nodes within the mesh.
RMEs configure the RPL protocol to ensure routes are loop-free by disallowing nodes from selecting DODAG parents that are
positioned further away from the CGR.
Route Redistribution of External RPL Routes
CG WPAN module for Cisco Resilient Mesh supports route redistribution of external RPL routes in Cisco Resilient Mesh networks
for application modules and MAP-T addresses in DA networks. (See Configuring Redistribution of RPL in Other Routing Protocols,
on page 34).
IPv6 Unicast Forwarding
RMEs implement a route-over architecture where forwarding occurs at the network layer. RMEs examine every IPv6 datagram that
they receive and determine the next-hop destination based on information contained in the IPv6 header. RMEs do not use any
information from the link-layer header to perform next-hop determination.
RMEs implement the options for carrying RPL information in Data-Plane datagrams ( RFC 6553 ) and Type 4 routing header as
specified for RPL in RFC 6554 . The routing header allows a node to specify each hop that a datagram must follow to reach its
destination.
The RME communication stack offers four priority queues for QoS and supports differentiated classes of service when forwarding
IPv6 datagrams to manage interactions between different application traffic flows as well as control-plane traffic. RMEs implement
a strict-priority queuing policy, where higher-priority traffic always takes priority over lower-priority traffic.
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