http/1.1 "Persistent" connection

First, persistent connection

(1) http/1.1 gradually stopped supporting the keep-alive connection, replacing it with an improved design called persistent connection (persistent connection), with the same purpose as the keep-alive connection, but with a better working mechanism.
(2) http/1.1 persistent connection is activated by default, and the application must add a Connection:close header to close the connection after the transaction finishes
(3) Client and server can close idle connection at any time

Ii. Limitations of persistent connections

(1) After sending the Connection:close request header, the client will no longer be able to send more requests on that connection.
(2) The connection can persist only if all messages on the connection have the correct custom message length (content-length)
(3) The http/1.1 agent must be able to manage the persistent connection with the client and the server separately
(4) http/1.1 Proxy Server should not establish a persistent connection with the http/1.0 client
(5) A client can maintain up to two persistent connections to any server or agent in case the server is overloaded

http/1.1 "Persistent" connection