When the user calls the RPC interface with a single connection to the same server, the framework guarantee that once the TCP connection has been established, the first request on the connection will contain the authentication string generated by `GenerateCredential`. Subsequent requests will not carried that string. The entire sending process is still highly concurrent since it won't wait for the authentication result. If the verification succeeds, all requests return without error. Otherwise, if the verification fails, generally the server will close the connection and those requests will receive the corresponding error.
Currently only those protocols support client authentication: brpc protocol (default protocol), HTTP, hulu, and ESP. For customized protocols, generally speaking, users could call the `Authenticator`'s interface to generate authentication string during the request packing process in order to support authentication.
Currently only those protocols support client authentication: [baidu_std](../cn/baidu_std.md)(default protocol), HTTP, hulu_pbrpc, ESP. For customized protocols, generally speaking, users could call the `Authenticator`'s interface to generate authentication string during the request packing process in order to support authentication.
