PIM-SM requires the following components: a Rendez-vous Point, shared trees, source trees.

PIM Register and Register Stop messages 

PIM register messages are sent by a PIM router to the Rendez-vous Point when it [the PIM router] receives multicast traffic from a streaming source. 

PIM RP sends a PIM register stop message to signal to the PIM router that it [the RP] has received the PIM register message.

Incoming Interfaces vs Outgoing Interface List

Incoming Interface

The PIM router’s interface that receives – or is supposed to receive – multicast traffic from the multicast source.

Reminder Of The Communication Models

client/server behind-NAT devices Point-to-point Hybrid Unicast Multicast

Multicast concepts

Multicast clients must join multicast groups in order to receive multicast traffic.

• IP host: an IP endpoint that is connected to a multicast router.
• Multicast router: a router that supports multicast protocols such as PIM and IGMP.
• upstream router
• downstream router
• multicast group
• nulticast (source, group) pair
• multicast group membership
• interested node
• Host Membership Query
• Host Membership Query
• Host Membership Report
• random report delay timer
• shared tree
• source-rooted spanning tree
• Multicast Distribution Tree
• parent link
• child link
• active branches
• multicast leaf router: is connected to leaf sub-networks
• Leaf sub-network: some have group members, some do not.
• DVMRP

Advantages of Multicast Communication

Routers process one packet instead of many (in case of multiple unicast transmissions) Routers do not have to determine the destination address to send the packet to, in contrast to unicast transmission. Reduced usage of resources: router CPU and memory, network bandwidth.