Overview

You need to add at least one listener after you have created a load balancer. This listener receives requests from clients and routes requests to backend servers using the protocol, port, and load balancing algorithm you select.

Supported Protocols

ELB provides load balancing at both Layer 4 and Layer 7.

Select TCP or UDP for load balancing at Layer 4 and HTTP or HTTPS at Layer 7.

**Table 1** Protocols supported by ELB
Protocol		Description	Application Scenario
Layer 4	TCP	Source IP address-based sticky sessions Fast data transfer	Scenarios that require high reliability and data accuracy, such as file transfer, email, and remote login Web applications that receive a large number of concurrent requests and require high performance
Layer 4	UDP	Low reliability Fast data transfer	Scenarios that require quick response, such as video chat, gaming, and real-time financial quotations
Layer 7	HTTP	Cookie-based sticky sessions X-Forward-For request header	Web applications where data content needs to be identified, such as mobile games
Layer 7	HTTPS	An extension of HTTP for encrypted data transmission to prevent unauthorized access Encryption and decryption performed on load balancers Multiple versions of encryption protocols and cipher suites	Web applications that require encrypted transmission