Azure ExpressRoute = AWS Direct Connect = Google Cloud Interconnect

All 3 are ways to connect your private datacenter or on-premise location (maybe your corporate office) directly to the cloud provider's network over a fast private link, like an industrial-sized VPN. This way you can access your cloud servers/services over this private connection rather than the public internet. Lots of companies do this if they have sensitive data or have their own "cloud" system running VMWare or something and want to augment with public providers.

This article is discussing lower-level infrastructure describing Google's global network components, from load-balancing, routing, internal datacenter connections to servers, etc.

Very cool, thank you for explaining. Is VPN the primary purpose or could it in theory be extended to work as software routers (as opposed to physical switches your traffic goes through) for all internet traffic once connect?

Let me know if I'm way off base in my understanding.

Well VPN = virtual private network, and that's exactly what it's creating. What you use it for is up to you.

You can access all Google Cloud services over this link and but you can also change your routes to point all internet traffic over this link too (you'll need some cloud VMs with public IPs to be the exit nodes). Not sure what you'd gain from doing that though.

Thanks for explaining.

Do you know if such a VPN is fundamentally different from something like OpenVPN, which can also be used site-to-site?

Functionally it's the same outcome, however these are managed solutions that the cloud provider (usually along with a networking partner) setup and maintain. This leads to much better reliability and speed and it's also not running over the public internet like a typical VPN so it's better for handling sensitive data access.

ExpressRoute is just Azure's version of AWS VPC. They're complicated VPNs for cloud services.

Espresso is a system for controlling BGP peering using application-fed metrics. It's basically complicated source routing.

Thanks for the response.

Couldn't ExpressRoute (and not familiar with AWS VPC) in theory be configured at multiple global locations to handle internet traffic?