Protocols in the presentation layer deal with proper data translation and encoding/decoding, such as External Data Representation (XDR). In addition, because of of the presentation layers role in encryption, you'll find the following protocols:

• Transport Layer Security (TLS)/Secure Socket Layer (SSL): Secures end-to-end communications such as bank transactions and web page retrieval using encryption
• Secure/Multipart Internet Mail Extensions (S/MIME): Digitally signs and encrypts email messages

At the presentation layer, the PDU is still data, where we see the data being translated or converted into the correct format. The following is a summary of the presentation layer:

In many ways, the presentation layer is an extension of the application layer. The next layer is the session layer, where we see all key elements of session management.