1. A multi-domain routing computation method, comprising: when it is determined that there are two or more domains deployed with a Path Computation Elements (PCE) in a network, computing a routing path, between a PCE of a first domain and a PCE of a last domain among the two or more domains deployed with a PCE, using an extended Backward-Recursive PCE-Based Computation (BRPC) algorithm, and computing a routing path using a Routing Controller (RC) in domains other than the two or more domains deployed with a PCE.