9.4 Load Balancing Explained

Key Concepts

• Load Balancing Overview
• Load Balancing Algorithms
• Health Checks
• Session Persistence
• Configuration and Implementation

1. Load Balancing Overview

Load balancing is the process of distributing network traffic across multiple servers to ensure no single server is overwhelmed. This improves performance, reliability, and availability of applications and services.

Example: Think of load balancing as a traffic cop directing cars at a busy intersection. Just as the traffic cop ensures no single road becomes congested, load balancing ensures no single server becomes overloaded.

2. Load Balancing Algorithms

Load balancing algorithms determine how traffic is distributed among servers. Common algorithms include:

• Round Robin: Traffic is distributed sequentially to each server in a cyclic order.
• Least Connections: Traffic is directed to the server with the fewest active connections.
• IP Hash: Traffic is directed based on the client's IP address, ensuring consistent server assignment for the same client.
• Weighted Round Robin: Servers with higher capacity receive a larger share of traffic based on assigned weights.

Example: Consider load balancing algorithms as different methods of distributing tasks among workers. Round Robin is like assigning tasks in a rotating order, Least Connections is like giving tasks to the least busy worker, IP Hash is like assigning tasks based on the worker's unique ID, and Weighted Round Robin is like giving more tasks to stronger workers.

3. Health Checks

Health checks are periodic tests to ensure that servers are functioning correctly. If a server fails a health check, it is removed from the load balancing pool until it recovers.

Example: Think of health checks as regular maintenance checks for machines. Just as a mechanic ensures machines are in good working condition, health checks ensure servers are operational and capable of handling traffic.

4. Session Persistence

Session persistence ensures that requests from the same client are directed to the same server. This is important for applications that require maintaining session state, such as shopping carts or login sessions.

Example: Consider session persistence as a VIP service at a restaurant. Just as a VIP customer is always seated by the same waiter, session persistence ensures a client is always served by the same server.

5. Configuration and Implementation

Configuring load balancing on a MikroTik router involves several steps:

• Define Servers: Specify the IP addresses and ports of the backend servers.
• Select Algorithm: Choose the load balancing algorithm that best suits your needs.
• Set Health Checks: Configure periodic health checks to monitor server status.
• Enable Session Persistence: Set up session persistence if required by your application.
• Apply Rules: Apply the configured rules to the appropriate interfaces or firewall chains to enforce load balancing policies.
• Test and Monitor: Ensure the load balancing setup is functioning correctly and monitor server performance.

Example: Configuring load balancing is like setting up a relay race. You need to identify the runners (servers), decide the order of relay (algorithm), ensure each runner is fit (health checks), maintain team cohesion (session persistence), and ensure the race runs smoothly (apply rules and monitor).