Frontend Protocol

A frontend protocol is used by a listener of a load balancer to receive requests from the clients. You can select a frontend protocol and port based on your service requirements.

The frontend protocol of a listener cannot be changed. If you want to use a different protocol, add another listener.

**Table 1** Frontend protocols
Load Balancing Type	Frontend Protocol	Application Scenario
Network load balancing	TCP	Scenarios that require high reliability and data accuracy, such as file transfer, email, and remote login Web applications that do not need to handle a large number of concurrent requests and do not have demanding performance requirements
	UDP	Scenarios that require quick response, such as video chat, gaming, and real-time financial news
	TLS	Scenarios that require ultra-high performance and large-scale TLS offloading
Application load balancing	HTTP	Applications that require content identification, for example, web applications and mobile games
	HTTPS	Workloads that require encrypted transmission, such as e-commerce and financial services
	QUIC	Applications with a poor network environment and whose users have to switch between networks

Backend Protocol

A backend protocol is used by backend servers in the backend server group to receive requests from a load balancer. You need to select a backend protocol when creating a backend server group. The backend protocol must match the frontend protocol.

Frontend and Backend Protocol Matching

The backend protocol of a backend server group must match the frontend protocol of the listener as described in Table 2.

**Table 2** The frontend and backend protocol matching
Load Balancing Type	Frontend Protocol	Backend Protocol
Network load balancing	TCP	TCP
Network load balancing	UDP	UDP QUIC
Network load balancing	TLS	TLS TCP
Application load balancing	HTTP	HTTP
Application load balancing	HTTPS	HTTP HTTPS GRPC
Application load balancing	QUIC	HTTP HTTPS