Load Balancing

Distributing network or application traffic across multiple servers.

Edit Concept ✏️

Load Balancing

Load balancing refers to the process of distributing incoming network traffic across a group of backend servers, also known as a server farm or server pool.

Key Functions

  • Distributes client requests or network load efficiently across multiple servers.
  • Ensures high availability and reliability by sending requests only to servers that are online.
  • Provides the flexibility to add or subtract servers as demand dictates.

Common Algorithms

  1. Round Robin: Successive requests are delegated to the next server in the list.
  2. Least Connections: Sends requests to the server with the fewest active connections.
  3. IP Hash: The client’s IP address is used to determine which server receives the request (good for session persistence).
  4. Weighted Round Robin/Least Connections: Servers are assigned weights based on their capacity.

L4 vs. L7 Load Balancing

  • Layer 4 (Transport): Based on data from network and transport layer protocols (IP address and TCP port). It is fast but doesn’t “look” at the content of the request.
  • Layer 7 (Application): Based on the content of the request (URL, headers, cookies). It allows for more complex routing (e.g., sending /api requests to one pool and /static to another).