ADVPN or Auto Discovery VPNs

https://www.juniper.net/documentation/en_US/junos/topics/topic-map/security-auto-discovery-vpns.html

Understanding Auto Discovery VPN

Auto Discovery VPN (ADVPN) is a technology that allows the central HUB to dynamically inform spokes about a better path for traffic between two spokes. When both spokes acknowledge the information from the HUB, they establish a shortcut tunnel and change the routing topology for the host to reach the other side without sending traffic through the HUB.

Config:

https://www.juniper.net/documentation/en_US/junos/topics/reference/configuration-statement/advpn-edit-security.html