What is Load balancer?

• Distributes load across multiple machines
• Considerations:
  • Load balancers should not forward requests to Un healthy Servers. For this the load balancers have Health Checks (Health Probes).
  • For Health Checks two popular checks are
    • TCP Ping: Check whether port is responding
    • HTTP Ping: Check whether web site is responding or not. Health checks are done using HTTP Status Codes

Load Balancers are of Two Types

• We have two types of load balancers.
  • Layer 4 Load balancers:
    • Protocol: TCP or UDP
    • Ports
  • Layer 7 Load Balancers:
    • HTTP(S)
    • Ports
    • URI
• These are based of OSI Networking Model. Refer Here

Non Cloud Load Balancers

• F5
• HA-Proxy
• nginx as load balancer

Most Widely use Load Balancer Setup

How about the same setup in Azure

• Layer 4 load balancer => Azure Load balancer
• Layer 7 Load Balancer => Application Gateway
• DNS => Azure DNS

Azure Reference Architecture