This topic introduces the common terms related to WAF.
back-to-origin IP address
A back-to-origin IP address is an IP address that WAF uses to establish network connections with an origin server.
WAF uses specified back-to-origin CIDR blocks to forward service traffic back to the origin server. After you activate WAF to protect your website, we recommend that you configure the WAF back-to-origin CIDR blocks on the origin server to prevent service traffic from being blocked. For more information, see Obtain WAF back-to-origin CIDR blocks.
An origin server is a backend server that provides services.
A web application is an application that users can access through a web browser.
Layer 4 proxy
A Layer 4 proxy is a proxy server that analyzes only destination address and port information in a request. The Layer 4 proxy forwards the request to an origin server based on specified rules.
Layer 7 proxy
A Layer 7 proxy is a proxy server that analyzes the application content and specific fields in a request. The Layer 7 proxy forwards the request to the origin server based on specified rules.