Transport Layer Basics

The Transport Layer (TL) is a Windows Service the DSM infrastructure components (Relay Proxy, Event Transport) use to communicate. The Transport Layer may be configured as server and as client at the same time and can set up any number of connections to other Transport Layers. If a connection has already been set up to a Transport Layer, it will remain open and serves as an encrypted communication channel for other components. Therefore the direction of the data flow does not depend on defined firewall rules.

In this example, the firewall blocks the complete network traffic from domain A > domain B. With the help of an active Transport Layer connection (which was initiated by the Transport Layer in domain B), however, the Relay Proxy is able to transfer the client requests from domain A to the Client Web Service in domain B even if the firewall is active.