Source-route transparent (SRT) bridging is a bridging scheme developed by IBM that combines source-route bridging (SRB) and transparent bridging in the same network. SRT is commonly used with token ring networks.
Transparent bridging was first developed by Digital Equipment Corporation in the early 1980s and has become IEEE standard 802.1. A transparent bridge learns the network's topology from the source address of each incoming frame. It then uses this information to create a table of the paths used by the hosts so that it can use the same paths to forward network traffic. Network hosts do not detect the presence or operation of transparent bridges.
When an SRT bridge receives a frame, it immediately checks the frame's routing information indicator (RII) bit to see if the frame is a transparent bridging frame or an SRB frame. Once it determines the frame's type, it processes it accordingly.