ELB & ASG

Elastic Load Balancing & Auto Scaling Groups

Before diving into the explanations of ELB & ASG we should understand what they are. So let's start with the Load Balancers.

What is a Load Balancer?

Load balancers are the servers that forward traffic to multiple servers (like EC2 instances) downstream.

Why use a Load Balancer?

• Spread the loads to multiple downstream instances

• Expose a single point of access (DNS) to your application

• Handle failures seamlessly and do regular health checks

• Provide SSL termination for your websites

• High availability across zones

• Separate public traffic from private traffic

What is AWS Elastic Load Balancer ?

Elastic Load Balancer (ELB) is managed load balancer.

• AWS takes care of upgrades, maintenance and availability

• AWS guarantees that it will be working

• It costs less setup your own load balancers

• Integrated with lots of AWS services

ELB Types

You will see the types of load balancers. It is always recommended to use new generations.

• Classic Load Balancer (Deprecated) -> Old generation. HTTP, HTTPS, TCP, SSL

• Application Load Balancer -> HTTP, HTTPS, Websocket

• Network Load Balancer -> TCP, TLS, UDP

• Gateway Load Balancer -> Operates at layer 3 (IP Protocol)

What is ALB?

Application Load Balancers is Layer 7

• Load balancing to multiple applications on the same machine

• Load balancing to multiple HTTP apps across machines

• Support HTTP/2 and WebSocket

• Support redirects (HTTP to HTTPS etc.)

• Routing tables to different target groups

• Great fit for microservices and containerized apps

• Preserve client IP information on the X-Forwarded-For header

ALB Target Groups

We can think of target groups as the destinations that load balancer routes the traffic

• EC2 Instances

• ECS tasks

• Lambda Functions

• IP Addresses (private IPs)

ALB can route multiple target groups

What is NLB?

NLB is OSI Layer 4 load balancer.

• The target type is IP and EC2 instances

• Supports TCP, UDP and TLS protocols

• Support Static IP address

• SSL termination -> Load balancer or target

• Natively support IP preservation of client unlike ALB

• Ultra-low latency

What is GWLB?

GWLB is OSI Layer 3 load balancer.

• Deploy, scale and manage 3rd party network virtual appliances in AWS

• Examples: Firewalls, Intrusion Detection and Prevention Systems, Deep Packet Inspection Systems, payload manipulation etc.

• Operates at Layer 3 (Network Layer) - IP Packets

• Combines Transparent Network Gateway ( single entry point for all traffic) and Load balancer (distributes traffic to your virtual appliances)

• Uses the GENEVE protocol on port 6081

• Target Groups are EC2 Instances and IP addresses (must be private)