A framework for handling route changes and aggregation in IPSOFACTO

IPSOFACTO (IP Switching Over Fast ATM Cell Transport) is an IP switching technique that directly maps IP flows to ATM VCs without any signalling. A switched path for a new flow is setup while routing the first packet through the network. Subsequent packets are forwarded entirely at the cell-level through the switched path, and no further packet-level routing decision is taken at the intermediate nodes. This paper considers how changes in the network topology, as expressed through IP routing tables, can be correctly reflected back into the cell switched path associated with a flow. A simple scheme based on IP source routing and IP-in-IP encapsulation is proposed, which ensures that the impact of route changes is handled in a consistent manner exclusively by the ingress routers of an IPSOFACTO cloud. This scheme is further used by interior routers to identify point-to-point flows that can be aggregated and merged into a multipoint-to-point switched path, thus reducing the VC usage within an IPSOFACTO network. This scheme also allows switched paths with different classes-of-service to be setup within the cloud, when used in conjunction with RSVP. It relies on the underlying routing protocol to either provide a complete topology of the network (e.g. OSPF) or a complete path between every ingress-egress pair (e.g. BGP).