Oracle Cloud's secure VPN service that creates encrypted network tunnels over the internet. Like sending mail in a locked, tamper-proof box - even if someone intercepts it, they can't read what's inside.
A government agency uses IPSec Connection to securely transmit classified data between their headquarters and Oracle Cloud infrastructure.
All four provide managed, encrypted IPsec tunnels over the public internet to connect on-premises networks (or another cloud) to a cloud VPC/VNet/VCN. OCI uses an IPSec Connection attached to a DRG; AWS uses a Site-to-Site VPN attached to a Virtual Private Gateway or Transit Gateway; Azure uses VPN Gateway attached to a VNet; GCP uses Cloud VPN attached to a VPC network. They differ mainly in routing options (BGP vs static), HA design, and throughput/SLAs.