Recently routing protocols for QoS aware multicast have been actively studied, but there are few studies focusing on the scalability of link state advertisement when the available bandwidth of a link is updated along with the QoS aware multicast tree construction. This paper proposes a new QoS aware multicast routing protocol that is scalable in terms of the link state advertisement exchange. Our protocol has the following features: (1) a multicast network is divided into domains, and the advertisement of information on links within a domain is limited within the domain; (2) among the border multicast routers, only the link state information of interdomain links is advertised, so that the number of link state advertisement messages is drastically reduced; (3) when a multicast tree spreads over multiple domains, the tree construction needs to be performed without information on links in other domains, and it is possible that the construction may fail. In order to cope with this problem, the crank back mechanism of tree construction is introduced. This paper describes the detailed procedures and the message formats of our protocol. It also describes the evaluation of the number of exchanged link state advertisement messages and shows that our protocol can reduce the number by the order of 1/(number of domains) compared with conventional protocols.