There are two fundamental areas of concern for securing communications: transport security and message security.
Transport Security
Transport security is used to provide point-to-point security between the two endpoints. Common approaches to transport security are Secure Sockets Layer (SSL) encryption and Internet Protocol Security (IPSec).
Message Security
Message security can be used with any transport protocol. You should protect the content of individual messages passing over the channel whenever they pass outside your own secure network, and even within your network for highly sensitive content. Common approaches to message security are encryption and digital signatures.
Always keep in mind that message security generally has a higher impact on communication performance than transport security. You can use partial or selective message encryption and signing to improve overall performance.