Transparent interconnection of incompatible local area networks using bridges
Radia Perlman, George Varghese · 1987
No single LAN technology is sufficient to interconnect all the computers in a given plant, campus, or site. Thus it is desirable to combine different types of LANs, using a device called a Bridge, to produce an Extended LAN. Some LANs in the Extended LAN may have incompatible Data Link formats. Thus a bridge may need to encapsulate a frame originating on LAN A inside the Data Link header of another (incompatible) LAN B in order to allow the type A frame to travel over LAN B. In general, frames sent between any pair of LANs in the Extended LAN must be encapsulated across every incompatible LAN in the path between the LANs.