Some hosts cannot correctly process this field, in which case translational bridges are forced to drop those frames that exceed Ethernet's MTU size. Bits representing Token Ring functions that have no Ethernet corollary typically are thrown out by translational bridges. Some bridge manufacturers simply ignore the bits. In the former case, a Token Ring source node determines whether the frame it sent has become lost. Proponents of this approach suggest that reliability mechanisms, such as the tracking of lost frames, are better left for implementation in Layer 4 of the OSI model.
Translational bridges can create a software gateway between the two domains.
The ring number, in this case, actually reflects the entire transparent-bridging domain. To the transparent-bridging domain, the translational bridge is simply another transparent bridge. When bridging from the SRB domain to the transparent-bridging domain, SRB information is removed. RIFs usually are cached for use by subsequent return traffic. When bridging from the transparent bridging to the SRB domain, the translational bridge can check the frame to see if it has a unicast destination.