AWS Learning: Gateway Load Balancer Basics
We use load balancers to distribute traffic across multiple targets such as EC2 instances and as you might already know, AWS offers several types of load balancers:
- Application Load Balancers
- Network Load Balancers
- Classic Load Balancers
- Gateway Load Balancers
Gateway Load Balancer is the newest type of load balancer from AWS so I started to have a look at understanding the basics. I did it initially to have at least some minimal understanding before going to the AWS Certified Solutions Architect Associate exam, even though most of the courses mentioned most likely this won’t be an exam topic.
Context of usage: sometimes we need our traffic to be inspected by a third party appliance before sending it to it’s targeted destination. A third party appliance could be a firewall or an analytics system.
Please see the list of appliance vendors from AWS, it might give you a better undestanding over what an appliance means: https://aws.amazon.com/elasticloadbalancing/partners/
In the below example we need to send traffic from a Source to a Target, but we want that traffic to be inspected by a virtual appliance first. In order to achieve that we will use a Gateway Load Balancer(GWLB). So the source traffic will be first sent to the load balancer, which routes the traffic to an appliance for inspection. If everything is alright, the flow continues and the traffic is forwarded from the Gateway Load Balancer to the Target. The Target replies to the load balancer but the reply is sent back to the Source only after the output traffic has been also sent to the appliance for inspection.
The traffic between the Gateway Load Balancer and the appliance is exchanged using the GENEVE (Generic Network Virtualization Encapsulation) protocol on port 6081.
The Gateway Load Balancer operates at layer 3, the network layer (Open Systems Interconnection OSI model). This article might help in undestanding this part: Understanding the OSI Model
I personally didn’t have a need to use a Gateway Load Balancer in real life, but if you had please add examples in the comments section.
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Also if you’re planning to study for AWS Certified Solutions Architect Associate check out my learning materials here.