This repo contains terraform configuration to instantiate sets of anycast DNS servers with a test record hello-world.test. We use BIND 9 and AWS Global Accelerator, amazon's anycast service.

⚠️ This demo has been updated to avoid a previous use of AWS ELB, and now routes UDP traffic directly from the AWS Global Accelerator to EC2 instances. For the previous, ELB-dependent topology, see the ga_to_elb directory.

AWS Traffic Flow Configuration

graph LR
subgraph Global Accelerator
	aws_globalaccelerator["GA"]
	aws_globalaccelerator_listener["GA Listener"]
end
subgraph Per-Region Resources
	aws_globalaccelerator_endpoint_group["GA Endpoint Group"]
  aws_instance_01["EC2 Instance dns01"]
  aws_instance_02["EC2 Instance dns02"]
end

aws_globalaccelerator --> aws_globalaccelerator_listener
aws_globalaccelerator_listener --> aws_globalaccelerator_endpoint_group
aws_globalaccelerator_endpoint_group --> aws_instance_01
aws_globalaccelerator_endpoint_group --> aws_instance_02

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Show and Tell

A GIF recording is available, below. Here are the commands used in that show & tell session:

• First you must have terraform installed, and ensure you have AWS credentials setup with adequate permission to create instances, global accelerators, and so on. I simply used a super-user account.
• terraform init to get the working directory ready
• terraform plan to do a dry run and see what will happen
• terraform apply to deploy your globally-anycasted name servers
• aws --region us-west-2 globalaccelerator list-accelerators to show your GA's IP addresses
• host hello-world.test <IP address of global accelerator> to run a DNS query against your new server!
•  ⚠️ your first DNS query to the anycast address will probably fail! It may take 20 minutes for a new Global Accelerator to start functioning. The animated GIF makes it look quick, but that's Hollywood trickery.
• Try that host hello-world.test <IP address> command again after lunch. It should succeed!
• terraform destroy to tear it all down so you won't keep spending money at the rate of $1 per hour

AWS Cost

As of 2021-11-20 the cost of this is approximately:

Component	Per-Region / Global	Cost Range / Region	Cost MRC Ext
Global Accelerator	Global		$18
DNS Server VMs t4g.nano	Capacity-Based Per-Region × 17	$3.03 - $4.83	$82.11

DDOS Concerns

The speed at which GlobalAccelerator can scale in response to DDOS should be evaluated.