A network component comprising: a first and a second path computation element (320, 420, 520, 620 and 720), PCE, configured to perform impairment aware routing and wavelength assignment, IA-RWA, by: establishing a path computation element protocol, PCEP, session with a path computation client, PCC; the first and second PCE (320, 322) being adapted to: receive by the first PCE a path computation request from the PCC with path computation information comprising routing and wavelength assignment, RWA, information and constraints; perform by the first PCE, impairment aware RWA, IA-RWA, based on the path computation information and a private impairment information for a vendor' s equipment for a plurality of network elements, NEs, in an optical network using routing and combined wavelength assignment, WA, and impairment validation; IV; and send by the first PCE to the PCC a final list of validated paths and an assigned wavelength based on the IA-RWA, characterized in that to perform by the first PCE IA-RWA the first PCE and the second PCE are further adapted to: generate by the first PCE a set of validated paths based on impairment information using IV approximation techniques; perform by the first PCE RWA on the generated set of validated paths; send by the first PCE to the second PCE a list of computed and validated paths and assigned wavelength; perform by the second PCE a detailed IV for the list of computed and validated paths and assigned wavelength; and send by the second PCE to the first PCE the final list of validated paths and assigned wavelength. establishing a path computation element protocol, PCEP, session with a path computation client, PCC; the first and second PCE (320, 322) being adapted to: receive by the first PCE a path computation request from the PCC with path computation information comprising routing and wavelength assignment, RWA, information and constraints; perform by the first PCE, impairment aware RWA, IA-RWA, based on the path computation information and a private impairment information for a vendor' s equipment for a plurality of network elements, NEs, in an optical network using routing and combined wavelength assignment, WA, and impairment validation; IV; and send by the first PCE to the PCC a final list of validated paths and an assigned wavelength based on the IA-RWA, receive by the first PCE a path computation request from the PCC with path computation information comprising routing and wavelength assignment, RWA, information and constraints; perform by the first PCE, impairment aware RWA, IA-RWA, based on the path computation information and a private impairment information for a vendor' s equipment for a plurality of network elements, NEs, in an optical network using routing and combined wavelength assignment, WA, and impairment validation; IV; and send by the first PCE to the PCC a final list of validated paths and an assigned wavelength based on the IA-RWA, characterized in that to perform by the first PCE IA-RWA the first PCE and the second PCE are further adapted to: generate by the first PCE a set of validated paths based on impairment information using IV approximation techniques; perform by the first PCE RWA on the generated set of validated paths; send by the first PCE to the second PCE a list of computed and validated paths and assigned wavelength; perform by the second PCE a detailed IV for the list of computed and validated paths and assigned wavelength; and send by the second PCE to the first PCE the final list of validated paths and assigned wavelength. generate by the first PCE a set of validated paths based on impairment information using IV approximation techniques; perform by the first PCE RWA on the generated set of validated paths; send by the first PCE to the second PCE a list of computed and validated paths and assigned wavelength; perform by the second PCE a detailed IV for the list of computed and validated paths and assigned wavelength; and send by the second PCE to the first PCE the final list of validated paths and assigned wavelength.