Multicasting is preferred over multiple unicasts from the viewpoint of better utilization of one of the most important network resources, namely network bandwidth. Multicasting can be done in two different ways: source based tree approach and shared tree approach. This research focuses on improving bandwidth utilization of source based multicast routing protocols and also provides core selection approaches for shared tree multicasting. In this work, we have defined new concepts called pseudo diameter and super pseudo diameter by using the routing information present in Distance Vector Routing (DVR) tables. Pseudo diameter relates to the physical locations of routers and is used to control the flow of packets along the broadcast tree. Super pseudo diameter relates to the physical location of group members and is used to control the flow of packets along the multicast tree. This location aspect of routers and group members have been incorporated into the existing broadcast and multicast protocols to achieve a much improved bandwidth utilization compared to the existing approaches. These concepts have also been used in developing both static and group based core selection approaches. Pseudo diameter used in static core selection approach, and super pseudo diameter used in group based core selection approach, generates secondary and tertiary cores along with primary core to achieve fault tolerance. Besides DVR, the other widely used unicast routing protocol is the Link State Routing protocol (LSR). We have shown that a similar concept to pseudo diameter called sub diameter can be used on networks using LSR tables to achieve better bandwidth utilization in source based multicasting and in selecting a core for shared tree multicasting.