After studying for Advanced Networking Exam, I pondered a question about global backbones. There is a need for common understanding. So let’s take a step back. Transit gateway was a service introduced at ReInvent 2018. Transit Gateway(TGW) puts a router between VPCs and other networking services. The transit gateway works by putting attachments in each VPC using ENIs. If you’re lost before proceeding, watch the Re: Invent Video. TGW uses attachments is fundamental to the VPC architecture as the VPC doesn’t process traffic from a source destination outside the VPC. So the attachment ENI becomes part of the VPC. So now I have an attachment in the VPC thru a subnet. So instead of terminating my DirectConnect Gateway(DXGW) on a VGW in a VPC, it’s terminated in a TGW. A quick whiteboard of this architecture.
This becomes challenging while building a global network because European network would look like this assuming I had three pops in one Europe region:
Still better than Direct Connect Gateways to the VPCs. But there is a limitation Transit Gateways which are peered, don’t dynamically pass routes. This works great if you summarize routes by region. Like the US was all 10.50.0.0/12, and Europe was all 10.100.0.0/12. What doesn’t work is when I have unsummarized routes. But I digress route summarization doesn’t matter to the question. So here is a quick view of our whiteboard architecture of Europe and US regions:
The question is if there was dynamic routing, could I use the AWS backbone to haul traffic around the world without having to build my own global network as the two TGWs would exchange my prefixes from the exchange or pop locations?