Elastic Load Balancer

• Elastic Load Balancers (ELB) are AWS managed load balancers
• AWS will take care of upgrades, maintenance and high availability of the load balancers
• It is integrated with many AWS offerings such as:
  • EC2, ASGs, Amazon ECS
  • AWS Certificate Manager (ACM)
  • CloudWatch
  • Route 53
  • AWS WAF, AWS Global Accelerator

Types of Load Balancers on AWS

• AWS offers 4 kinds of load balancers:
  • Classic Load Balancers (v1 - old generation) - CLB: supports HTTP, HTTPS, TCP, SSL (secure TCP)
  • Application Load Balancers (v2 - new generation) - ALB: supports HTTP, HTTPS, WebSockets
  • Network Load Balancer (v2 - new generation) - NLB : supports TCP, TLS, UDP
  • Gateway Load Balancers - GWLB: operates at layer 3 (Network Layer) - IP Protocol

ALB Listener Rules

• Rules on ALB are processed in order (default rule is going to be processed last)
• Each rule has a supported action: forward, redirect, fixed-response
• Rules can have conditions based on:
  • host-header
  • http-request-method
  • path-pattern
  • source-ip
  • http-header
  • query-string
• Target Group Weighting:
  • We can specify a weight for each Target Group on a single rule
  • Allows us to control the distribution of the traffic to our application

ELB DualStack Networking

• Allows clients to communicate with the ELB using both IPv4 and IPv6 (dualstack URL)
• Supported by both ALB and NLB
• ALB and NLB can have mixed IPv4 and IPv6 targets, but only separate target groups
• ELB dualstack ensures compatibility between clients and target IP versions:
  • IPv4 clients will communicate with IPv4 targets
  • IPv6 clients will communicate with IPv6 targets
  • In case there are only IPv4 targets, the ELB automatically converts requests from IPv6 to IPv4