Network Load Balancing
Network load balancing
What you will learn
- Explain a load balancer's core function of distributing requests across multiple servers.
- Recall two common load-balancing algorithms: round robin and least connections.
- Explain the health check's role in automatically removing failed servers.
- Connect a load balancer to the high-availability concept it supports.
A load balancer receives all incoming requests for a site or service and decides — via a specific algorithm, not randomly — which server in the pool handles each request. This lets it serve traffic beyond any single server's capacity, and keeps the service running if any one server fails on its own.
Core concepts
| Server Pool | The group of servers holding identical content that receives the distributed traffic. |
|---|---|
| Health Check | A periodic check on each server in the pool — one that fails the check is automatically removed from rotation until it recovers. |
Round Robin vs. Least Connections
| Round Robin | Least Connections | |
|---|---|---|
| Distribution method | Each server takes a turn, in order | The request goes to the server currently holding the fewest active connections |
| Best suited when | Servers are identical and request loads are roughly even | Request loads vary, or servers differ in capacity |
What matters on the exam
- A load balancer directly supports high availability (HA) — automatically removing a failed server is exactly a failover, at the server level.
- "We want to distribute traffic beyond one server's capacity while removing any failed server" = always a load balancer, never just a router or firewall.
Quick check
Answer in your head first, then reveal.
What is the health check's role in a load balancer?Reveal the answer
Automatically removing any server that fails the periodic check from the rotation, without manual intervention.
Which algorithm fits better when request loads vary across servers?Reveal the answer
Least connections.
How does a load balancer relate to high availability?Reveal the answer
Its immediate removal of a failed server is a form of failover that keeps the service running without noticeable interruption.
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Sources
Used to verify the facts. The writing is original to Passuit.