Inform Previous Parent on Reattach

To allow end devices (EDs) in a Thread network to inform their previous parent router that they have attached to a new parent router, enable the Inform Previous Parent on Reattach feature.

This updates the previous parent's child table quicker than the configured child timeout interval and prevents it from queueing traffic for an ED that it thinks is asleep, but in actuality has a new parent.

How it works

After an ED attaches to a new parent router, it sends a single unicast IPv6 message containing the following information to its previous parent router:

  • The Mesh-Local EID of the ED as the source address.
  • The Mesh-Local EID of the previous parent router as the destination address.
  • An empty payload.

This type of IPv6 message prompts the old parent router to immediately remove all registered IPv6 addresses for that ED from its child table.

How to enable

This feature is disabled by default.

To enable Inform Previous Parent on Reattach, define OPENTHREAD_CONFIG_INFORM_PREVIOUS_PARENT_ON_REATTACH as 1 in the openthread-core-default-config.h file, prior to building OpenThread:

#ifndef OPENTHREAD_CONFIG_INFORM_PREVIOUS_PARENT_ON_REATTACH
#define OPENTHREAD_CONFIG_INFORM_PREVIOUS_PARENT_ON_REATTACH 1
#endif

Parameters

There are no configurable parameters for this feature.

API

There is no public API for this feature.

CLI

There are no CLI commands related to this feature.