Security services use message protection.
The client uses the security mechanism to prepare the data packet it will send to the server.
For example, if the client requests message confidentiality, the security mechanism encrypts the commands that will be sent to the remote server. If the client requests out-of-sequence checking, the security mechanism time-stamps each data packet.
The client sends the data to the destination server.
When the server receives the data, it uses the security mechanism to perform the appropriate decryption or validation.
The server returns the results to the client, using the security mechanism to perform the security action requested. For example, the server returns results in encrypted form or time-stamps each data packet returned to the client.