The traffic in IP networks has increased, and the diversification of services has advanced in recent years. Therefore, network carriers request services that they can provide as soon as possible and want to use largescale networks for Next-Generation Network technologies. There is two kinds of problems. First is a taking a long time to develop new services. Second is a problem stemming from the processing of routing protocols using Interior Gateway Protocol in largescale IP networks such as carrier networks. As a solution for those problems, this paper presents a functionally distributed transport network architecture on NGN and a method to map routing functions to control-plane servers and routers where a routing process, performs route computation and distribution for multiple routers collectively. For the communication mechanism between routers and servers, the ForCES architecture model proposed in IETF is utilized. This paper also presents a routecomputation method using a link-state database that is configured based on suppressed representation of a network where a whole subnetwork is regarded as a router.