The transport layer handles the transmission, reception, and the transport of data that is provided by the communication layer.

To survive the loss of the transport layer connections (e.g. TCP connections) and resume with a new connection, the communication layer is responsible for re-establishing the transport layer connection without interrupting.

The transport layer can also be used to implement Confidentiality and Integrity by using HTTPS (HTTP messages over a TLS connection) as described in OPC 10000-6. It is important to note that HTTPS certificates can be (and often are) shared by multiple applications on a platform and that they can be compromised outside of the OPC UA usage of them. All applications on the platform that use the same shared certificate have the same settings. HTTPS does not require application Authentication, if this is required it can be included as part of Session establishment.