Network watchdog

The NW (Network Watchdog Timeout) feature allows a powered router to verify the presence of a coordinator if no communication events with the coordinator have occurred within a timeout period. This timeout is specified in minutes using the NW command. The default setting for the network watchdog feature is disabled (NW = 0) and can be configured for up to several days.

Anytime a router receives valid data from the coordinator or data collector, it clears the watchdog timeouts counter and restarts the watchdog timer.

The following events restart the network watchdog timer:

If any of the events listed above occur during the watchdog period then no additional network traffic will be generated. If the watchdog timer does expire (no valid data received for 1 NW time period), the router attempts to initiate communication with the coordinator by sending an IEEE 64-bit address discovery message to the coordinator. If the router cannot discover the address, it records one watchdog timeout. After three consecutive network watchdog timeouts expire (3 * NW) and the coordinator has not responded to the address discovery attempts, the router will enter one of three modes based on the configuration of DC (Joining Device Controls) bit 5 and DO (Miscellaneous Device Options) bit 7:

  1. No Network Locator (Leave Network): If neither DC bit 5 or DO bit 7 is set, the router will immediately leave the network and begin searching for a network to join based on its networking settings. If API mode is enabled, a network disassociated modem status frame (0x03) will be emitted when the router leaves the network. If the router finds and joins a new coordinator or the original coordinator, a joined network modem status frame (0x02) will be emitted if API mode is enabled.
  2. Network Locator with Network Leave: If DO bit 7 is set but DC bit 5 is not set, the behavior of JV and NW are modified. The router will remain on the network until a new network is found. The router starts scanning for a network across the channels of the Scan Channel mask (SC). Scanning occurs at a random interval of between 90 and 135 seconds. If API mode is enabled, a network watchdog scanning modem status frame (0x42) will be emitted when scanning begins. If the device finds a network on the old channel with the same OI and operating ID, the search mode ends. If the device finds a network with a new OI but satisfies the device's search for a matching ID and ZS, the device leaves the old network and joins the new network with the new OI. These leave and join actions will cause the router to emit a disassociated network modem status (0x03) and a joined network modem status frame (0x02) if API mode is enabled. This supports swapping or replacing a coordinator in a running network.
  3. Network Locator with Rejoin: If DC bit 5 is set, the router will begin scanning the current channel indefinitely in an attempt to find the coordinator on the original network or re-join the coordinator if it has moved to a new network. If API mode is enabled, a network watchdog scanning modem status frame (0x42) will be emitted when scanning begins. Scanning occurs at a random interval of between 90 and 135 seconds. If it finds the coordinator which must have a matching ID (extended PAN ID) with the same PAN ID (OI) or a new PAN ID, the router will rejoin the coordinator even if the coordinator is configured with a NJ of 0 (joining disabled). If the router finds the coordinator on the original network or rejoins coordinator on a new network, a joined network modem status frame (0x02) will be emitted if API mode is enabled.