Internetworking connectionless and connection-oriented networks

The use of connection-oriented networks for the transport of IP traffic is seen to have value to both users and service providers. Given the expectati on that most endpoint-generated traffic will be in the form of connectionle ss IP datagrams, we address the problem of how to internetwork a CL (IP) ne twork with a CO network. CO networks can be packet-switched or circuit-swit ched, Examples of packet-switched CO networks include ATM and MPLS networks , in which resource reservations are made at the ATM or shim layer, and IF- switch-based networks, in which resource reservations are made at the IP la yer. Examples of circuit-switched networks include SONET/SDH and WDM networ ks that consist of programmable optical crossconnects. We consider the inte rnetworking problem for two modes of operation of CO networks: provisioned, in which connections are set up a priori, and switched, in which connectio ns are set up on demand. The main focus of this article is on the more comp lex problem: the internetworking of CL IP networks with CO networks operate d in a switched mode. Our solution consists of (i) interworking user plane protocols with protocol conversion in some cases instead of always using pr otocol encapsulation, (ii) interworking routing protocols by either simply having gateways know routing information of both networks or having all nod es know routing information of both networks, and (iii) interworking signal ing protocols by using application- or transport-layer end-to-end handshake s to trigger connection setups through the CO network. We demonstrate throu ghput improvements with our integrated routing interworking scheme over the MPOA IP-ATM internetworking solution for two example networks.