The IEEE 802.5 RIF is structured as shown in Figure 25-2 . These fields are described in the summaries that follow. A IEEE 802.5 RIF is present in frames destined for other LANs. Used when the source node supplies the route in the RIF header. The route is collected as the frame traverses the network.
Bridges add to the frame their bridge number and ring number onto which the frame is forwarded.
The target destination will receive as many frames as routes to that destination. Only bridges in the spanning tree forward the frame, adding their bridge number and attached ring number as it is forwarded. The spanning-tree explorer reduces the number of frames sent during the discovery process. The value can range from 2 to 30 bytes. The source initially sets the largest frame size, but bridges can lower it if they cannot accommodate the requested size.