Updating quality of service reservation

A router or router (300) domain in a first administrative domain (142) of a telecommunications network (100), the first administrative domain (142) comprises a first end having a first direction, the first endpoint is associated a reservation for a session transiting through the router or router (300) domain between the first end and a second end point in a second administrative domain, characterized in that the router or router (300) domain comprises a module ( 310) reservation quality of service (QoS), the module (310) QoS reservation is able to: - receive a notification (2320) address modification related to the reservation from the first end through a first router or router (116) access, in which the notification (2320) address modification indicates that the first end point changes its first address by a second direction from the first end point is changing from the first router or router ( 116) to a second access router or router (126; 136) access; and - issuing a first message (2112) book on behalf of the second endpoint to the second router or router (126; 136) access.