Partner Interconnect provides connectivity between your on-premises network and your Virtual Private Cloud (VPC) network through a supported service provider. A Partner Interconnect connection is useful if your data center is in a physical location that can't reach a Dedicated Interconnect colocation facility, or your data needs don't warrant an entire 10-Gbps connection.
How does Partner Interconnect work?
Service providers have existing physical connections to Google's network that they make available for their customers to use. After you establish connectivity with a service provider, you can request a Partner Interconnect connection from your service provider. After the service provider provisions your connection, you can start passing traffic between your networks by using the service provider's network.