The Internet explosion has drastically increased the bandwidth demand of modern telecommunication networks and as optical networks provide an opportunity for the future Internet, it is expected that Internet providers will gradually replace their infrastructures with optical networks. The Internet is a decentralized set of networks (more than 29.000) known as domains or Autonomous Systems on a well-known network hierarchy. In this structure of the Internet selecting a route to forward traffic on an end to end scenario is known as Multi-domain or inter-domain routing. Multi-domain routing has been a well-known problem largely analyzed in pure IP (packet) networks. But there are still limitations in multi-domain routing in optical multi-domain networks. To address these problems, a detailed hierarchical routing and signaling framework for GMPLS based Dense Wave Division Multiplexing (DWDM) Multi-Domain framework is presented. The frame work adapts the full mesh topology abstraction scheme to improve routing scalability and lower inter-domain blocking probabilities in optical DWDM multi-domain networks.