Application-level multicast suffers some disadvantages in terms of high multicast delay, overloading at Rendezvous Point (RP) and single-point of failure. In this paper, we propose DINCast to optimize application-level shared-tree multicast. The general idea of DINCast is to form a special logical data loop and use this loop instead of the RP as multicast sources. To demonstrate its effectiveness, we first analyze multicast delay with the inclusion of transmission delay, queuing delay and propagation delay of a typical symmetrical shared-tree multicast. We evaluate three placement schemes of DINCast. Our simulation results show that DINCast is effective in optimizing the multicast delay over the shared-tree multicast and the reduced rate of multicast delay may be up to 50%. Next, for any multicast tree, we carry out further simulations to optimize multicast delay. The experimental results show that DINCast can achieve better performance than original shared-tree Multicast.