This paper proposes the integration of connection IP routing with fast connection oriented Asynchronous transfer mode (ATM) hardware. It uses a soft-state in the ATM hardware to cache the IP forwarding decision. The paper claims that other proposals to support IP routing over ATM network hide the real network topology from the IP layer by treating the data-link layer as a large opaque network cloud and the approach adopted in this paper will alleviate these concerns. It aims to harness the benefits of high capacity, bandwidth scalability and ability to support multiservice traffic provided by ATM. The authors adopt a flow classification approach to gain benefit of the switching hardware for associating an IP flow with a specific ATM virtual circuit.
The flow classification is provided using port-pair flow and host-pair flow. The flow classifier inspects the contents of the fields that characterize the flow and makes its decision based upon a local policy. A flow management protocol is provided in which the IP switch controller assigns a free Virtual circuit identifier (VCI) label to the input port on which the flow is received and a free label on its control port. A redirection message is then sent other to the upstream node direct the further traffic through this interface which can be directly switched in ATM hardware. The real benefit comes when the downstream node also redirects the flow to a specific VCI as the further traffic belonging to this flow can be directly switched within the ATM hardware without the involvement of IP switch controller. Further provisions have been made in the paper to provide the same Time to Live (TTL) in the flow identifier as it would have been if it were forwarded hop-by-hop. The checksum is taken care of by subtracting the TTL value at the origin of the switched flow to emulate the behavior of hop-by-hop when destination is reached. The authors strive for providing robustness to the protocol by introducing an adjacency protocol which enables a node to be sure that its neighbor has not changed. The lifetime of the inconsistent state in the network is limited by associating lifetimes with redirection messages. Further concepts of receiver initiation, point-to-point, multicast and Quality of service (QoS) have been discussed in relation to the discussed protocol. Further host-pair simulation experiments have been performed and it is shown that ATM switch discussed can handle approximately 3.7 times more traffic. However, the host-pair flow results in a large number of connections which is a big drawback.
