Part 2 of a six-part article:

1. Configuration and Troubleshooting TLS in Exchange Server
2. What is Transport Layer Security protocol?
3. How the TLS Protocol Works
4. How to configure TLS encryption on Microsoft Exchange 2003 server
5. Testing and Debugging TLS protocol on Microsoft Exchange 2003 server
6. What do I do if there is no TLS handshake?

TLS is a successor to Secure Sockets Layer protocol. TLS provides secure communications on the Internet for such things as e-mail, Internet faxing, and other data transfers. There are slight differences between SSL 3.0 and TLS 1.0, but the protocol remains substantially the same. It is good idea to keep in mind that TLS resides on the Application Layer of the OSI model. This will save you a lot of frustrations while debugging and troubleshooting encryption problems related to TLS.

The TLS Handshake Protocol allows the server and client to authenticate each other and to negotiate an encryption algorithm and cryptographic keys before data is exchanged. In a typical scenario, only the server is authenticated and its identity is ensured while the client remains unauthenticated. The mutual authentication of the servers requires public key deployment to clients. When a server and client communicate, TLS protocol ensures that no third party may eavesdrop, tamper with any message, and message forgery.

The TLS Protocol Version 1.0 is defined in RFC document RFC 2246.

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