AWS] What is ELB? (There are different types of ALB/CLB/NLB)

2021-03-08 2021-03-08

1 What is ELB?
2 What is Connection Draining?
3 What is SSL Termination?
4 Related Services
- 4.1 Reference Site

What is ELB?

ELB is a service that automatically distributes incoming application traffic to multiple targets such as EC2 instances, containers, IP addresses, and Lambda functions.

The three types are as follows

Each is intended for load balancing, but for different purposes.

What is CLB?

CLB is an old type of ELB and is basically not used for web applications except for cases specific to CLB such as those requiring load balancing at Layer 4.

ALB Features

Supports Layer 7; HTTP/HTTPS listener
Path routing available
Charged by load balancer capacity unit (LCU) usage based on time
Use DNS when specifying IP address because IP address is variable
Cross-zone load balancing enabled by default

ALB can create listeners with rules that forward requests based on URL paths.

This method is called path routing.

If you have a group of EC2 instances performing multiple tasks, you can use path routing to route traffic to multiple back-end services in a single ALB.

Features of NLB

L4 NAT load balancer to support TCP listeners
Return traffic does not go through NLB
Charged by LCU usage based on time
Can add NLB subnets
Both DNS and IP are available due to fixed IP
Higher performance processing than ALB
Cross zone load balancing disabled by default

NLB is a high-performance load balancer capable of handling millions of requests per second, functioning at the fourth layer of the OSI model. Path routing is feasible, but high-performance ELBs for fairly large systems

The load balancing function performs load balancing of EC2 instances across multiple AZs according to the load of the EC2 instances under the control.