UDP keep alives, TTL and billing

I think that the Time-to-Live (TTL) value doesn't directly influence billing in AWS. The TTL field in the IP header only specifies the maximum number of hops (i.e., passing through routers) that a packet is allowed before it must be discarded or returned.

However, to address the gist of your question, all traffic that enters and exits the Elastic Load Balancer (ELB) is subject to standard AWS data transfer costs. This includes any keep-alive traffic.

Specifically, data transfer IN from the internet to an Amazon ELB or Elastic IP address (when it's associated with an EC2 instance, NAT gateway, or Network Load Balancer) is free, but data transfer OUT from those resources to the internet is charged.

For a UDP keep-alive, which is essentially just small packets of data sent to ensure a connection remains open, the amount of data sent and received would typically be quite small, and therefore the costs would be relatively minimal. Still, this traffic would count toward your overall data transfer costs.

As for your Load Balancer, there would also be costs for load balancing hours and processed data (beyond the free tier).

If you're trying to minimize data transfer costs, some strategies might include minimizing the amount of unnecessary traffic (like excessive keep-alive traffic), using AWS CloudFront for caching static content, or compressing data before transferring it.