ND Proxy

The ND proxy functionality is based on RFC4389 (Neighbor Discovery Proxies) with some changes as the “downstream” segment is based on RPL and not NDP.

• Incoming PIO (Prefix Information Option) in RA is extracted and used to configure the DODAG prefix
• Incoming RIO (Route Information Option) in RA are extracted and stored in the 6LBR routing table
• Incoming NS targeting a WSN node are handled by the ND Proxy : If there is an existing entry for the WSN node in the routing table, the ND Proxy will send back a NA
• NS/NA proxy based on RPL DAO and No-Path DAO

NDP Feature	ND Proxy implementation
Router discovery	Standard Router Solicitation messages are sent by the 6LBR
Prefix discovery	On-link Prefix in received RA is used to set up the DIO propagated in the WSN
Address autoconfiguration	Prefix in received RA is used to configure the 6LBR address and is propagated into the DIO
Address resolution	The ND proxy will reply to NS targeting a known WSN node (i.e. present in the routing table) with a NA using the 6LBR link-layer address
Next-hop determination	Upstream WSN packet will be routed by the 6LBR and forwarded either to the on-link host or to the subnet Default Router
Neighbor unreachability detection (NUD)	6LBR uses No-Path DAO to remove WSN node no longer present, it will not send back a NA for a node not in the routing table anymore
Duplicate address detection (DAD)	ND Proxy honors DAD requests like address resolution and NUD
Redirect	Not implemented yet