Gateway Load Balancer is *HUGE* and brings a capability to the cloud that has never even existed in traditional/legacy datacenter networks. It's not "just" ECMP. Flows are symmetrical, and sticky! Let me explain ... https://twitter.com/ric__harvey/status/1326194491452256257

GWLB let's you spread incoming or outgoing traffic over multiple firewalls, intrusion detection devices, packet inspectors, etc. It's horizontal scaling for network appliances, running on EC2 Instances. So far so good ... that sounds like ECMP.

But ECMP in datacenter networks doesn't align "north-south" and "south-north" traffic for the same flows (network connections) over the same devices, and it also "scrambles" all of the traffic when you add or remove a node to do any scaling.

This means that a huge amount of work that goes into building enterprise / scalable network appliances is spent on proprietary mechanisms to re-assemble flows between nodes. Complicated multicast protocols are common.

GWLB provides bi-directional flow symmetry, and flow stickiness. That makes it much easier to develop a virtualized network function. There's no need to worry about recombobulating the flows. NFV developers can focus on the business functionality instead.

I don't think it's an overstatement to say that with for the first time, a very small team can develop network functionality that will be horizontally scalable and highly available. I'm excited to see what customers might build!

Good example: want to measure how much of your traffic is plaintext? You could build an application in a few hours that uses pcap, ebpf, or DPDK to scan the traffic for plaintext/randomness and categorize each flow ... and then plug it in to GWLB.