The present invention relates to a back up top tier bandwidth manager (160) adapted to back up a top tier bandwidth manager (120) upon fail-over of the top tier bandwidth manager (120) in an Internet Protocol, IP, network. Said IP network comprises the top tier bandwidth manager (120) comprising a resource map (130) and adapted to pre-allocate resources in bulk from a bottom tier of said IP network (150) via a bottom-tier bandwidth manager (140) also located in said IP network. The back up top tier bandwidth manager comprises further a copy of the resource map (130) of the top tier bandwidth manager (120) which it is backing up and means for synchronising states with the bottom tier bandwidth manager upon fail-over of the top tier bandwidth manager.