Multicasting is the technique that is used for sending packets to large number of users in IP network by using different types of source based and shared trees. The multicasting is commonly used in different applications of internet such as IPTV, Video Conferencing, Seminars, Web meeting and others. There are different practical applications that are commonly using the multicasting techniques such as iTV player, multiparty gaming and others. The multicasting provides more benefits and features as compare to unicast services. There are different types of protocols used for configuration of multicasting in IP networks such as Internet Group Management Protocol (IGMP), and Protocol Independent Multicast (PIM). These protocols are providing different functions in multicast networks such as IGMP provides efficient management of information about hosts and PIM provides services for transmitting video packets from source to multicast groups. The multicasting is depending on multicast group, whereas three modes of PIM can be used in IP network such as Dense mode, Sparse mode and Sparse-Dense mode. The dense mode is providing source based services in multicast network by flooding traffic directly from source to multicast groups in (S,G) fashion. The Sparse mode is using designated routers to function as rendezvous points in multicast network. The Sparse-dense mode is function as both dense and sparse mode. The rendezvous points can be deployed by using three different methods such as Static RP method, Dynamic RP with Auto-RP and Dynamic RP with Bootstrap routers. This report is helping Sleeze Company to understand the in depth information about multicasting networks, whereas explanations are provided in terms of PIM modes, RP deployment methods and recommendations to deploy multicast network in their hotel chains. 2. PIM Modes:The multicasting networks are heavily relying on Protocol Independent Multicast (PIM) protocol, whereas all services provided between multicast sources and membership hosts are decided by PIM protocols. The three different types of mode are used within PIM protocol, whereas these three modes differ with each other in terms of their operations and functions.

2.1 PIM Dense mode:The mode of PIM protocol recognised for flooding of multicast traffic among all the registered hosts of multicast networks is called as PIM Dense Mode. The operation of PIM dense mode is depending on two types of messages from membership hosts such as join and prune messages. All the hosts requesting to join the multicast group are flooded with multicast traffic until multicast source router receives the prune message from membership host. There are different functions of PIM dense mode in multicasting networks such as high security through encryption techniques, interactions of MGSB and IGMP, protection from denial of service attacks, source based tree management and services, and encoded unicast features. These functions are provided by PIM dense mode by using the mechanism of Reverse Path Forwarding (RPF), whereas all operations of dense mode are conducted through RPF mechanism. The source is sending traffic to multicast groups after receiving the join requests, whereas these sources stop sending multicast traffic after receiving prune message from hosts. There is no designated router required for this mode of PIM protocol, whereas sources can provide multicast services to different hosts in multicast network. (Minoli, 2008).The operation of PIM dense mode can be understood by explaining the RPF mechanism and Source based tree mechanism. During the IP multicast routing, the routers are forwarding the packets away from source in order to make progress along the distribution tree, whereas these packets are forwarded away to prevent routing loops. The tables are organised by using the reverse path mechanism, whereas multicast forwarding state of router is logically defining the reverse path from receive to root of distribution tree. The whole mechanism is called RPF mechanism, whereas PIM dense mode is using the RPF tables to multicast traffic from source to all willing hosts. The PIM dense mode is operating as Push model, whereas traffic is flooded to all PIM neighbours. All multicasting is depending on source and failure can result in closure of whole tree. (Cisco, 2001). The operation of PIM dense mode can be explained by provided figure 1.

Figure 1: Operation of PIM Dense mode for flooding multicast traffic (Cisco, 2001)2.2 PIM Sparse Mode:The mode of PIM protocol using shared tree mechanism for multicasting traffic in network by using the designated router is called PIM sparse mode. The designated routers are commonly known as rendezvous points, whereas these designated routers are responsible for managing and forwarding multicast packets to hosts without disturbing the multicast source. There can be single or multiple RPs in multicast network, whereas only one RP is active in multicast network. The active RP is collecting information about joining hosts through multicast routing table, whereas RPs are making specific source or any source based trees for multicasting packets. The Multicasting Routing Information Base MRIB is used for storing the information collected from multicast routing table about joining hosts. There are two versions of PIM sparse mode, whereas these two versions can support different techniques for deployment of RP such as static RP and bootstrap RP. There are different functions of PIM sparse mode such as efficient mechanism for failover of RP, auto selection of RP, mapping agents to determine RP, high security, less attacks and vulnerabilities, faster delivery of multicast packet, less interference with source, shared tree mechanism, proper identification of joining hosts, hello message mechanism, and high QoS features. (Harte, 2008). The operation of PIM sparse mode can be explained by understanding the shared tree mechanism. This PIM mode is using IGMP and MLD protocols for operation in shared tree; where as asserted messages are sent and processed for providing the routing metrics for destination host addresses. The shared tree multicasting is denoted by (*, G) in multicasting routing, whereas shared trees are using common root placed (RP) for sending packets to multicast groups. The unidirectional traffic from multicast groups are sent to RP, whereas RP is connected with source tree and respond back to requesting multicast group in shared tree multicasting mode. Thus, the whole operation is managed by RP in shared tree fashion, whereas fast responses are provided to multicast group through shared content mechanism. (Cisco, 2007). The given below figure 2 is showing the operation of PIM sparse mode with router D functioning as RP in shared tree multicasting.

Figure 2: Example of PIM sparse mode with router D as rendezvous point (Cisco, 2007)2.3 PIM Sparse Dense Mode:The mode of PIM protocol that uses both dense and sparse mode characteristics is known as PIM dense sparse mode. This mode is usually configured in mixed multicasting networks, where both sparse and dense multicasting is required. The functions of both dense and sparse mode can be obtained by using this combined mode, whereas whole mechanism is depending on multicast group. This mode is more suitable in large multicast networks, whereas most suitable technique with PIM sparse dense mode is based on selection of dynamic RP through Auto-RP technique. (Cisco, 2007). The major functions of this mode are high security, efficient quality of service, multi-mode operation, services for all multicast group, efficient delivery of multicast packets and support for multiple RPs. The operation of PIM sparse dense mode is similar to previous modes, depending on which mode is active for multicast group. The configuration is also same for enabling multicast services; only the command IP pim-sparse-dense is defined on each interface. This mode is also capable of operating in both source tree and shared tree multicast. The Auto-RP feature is considered the most beneficial function of PIM sparse dense mode for automatically selecting the RP with highest IP address. (Juniper, 2011; Cisco, 2007).