Flow labelled IP: a connectionless approach to ATM

A number of proposals for supporting the Internet protocol (IP) over ATM are under discussion in the networking community including: LAN emulation, classical IP over ATM, routing over large clouds, and multiprotocol over ATM. Each of these proposals hides the real network topology from the IP layer by treating the data link layer as a large, opaque, network cloud. We argue that this leads to complexity, inefficiency and duplication of functionality in the resulting network. We propose an alternative in which we discard the connection oriented nature of ATM and integrate fast ATM hardware directly with the IP, presenting the connectionless nature of the IP. We use a "soft" state in the ATM hardware to cache the IP forwarding decision. This enables further traffic on the same IP flow to be switched by the ATM hardware rather than forwarded by the IP software. We claim that this approach combines the simplicity, scalability, and robustness of the IP with the speed, capacity, and multiservice traffic capabilities of ATM.