Intelligent bridges and routers-a proposal for the LAN/MAN/B-ISDN environment

An interworking concept called intelligent interworking units (I ²Us) is proposed and applied to the interconnection of IEEE 802.X LANs, IEEE 802.6 distributed-queue dual bus (DQDB) metropolitan area networks (MANs), and asynchronous-transfer mode (ATM)-based broadband integrated services digital network (B-ISDN). Interworking units (IWUs) are necessary to provide flexible communication capabilities among all the above mentioned network types. Currently IWUs use a fixed layering scheme and are thus classified as bridges, routers, or gateways. The I²U concept enhances conventional IWUs to allow for more sophisticated operation in a high-speed environment. I ²Us dynamically select the layers for interworking according to the received type of data. This avoids encapsulation at the source IWU and makes use of Layer 3 network functions only when needed. An overview of the provision of connectionless services in the three network types is given. The I²U concept for the interconnection of LANs via MANs and of MANs via the B-ISDN is described