CANOGA PERKINS CanogaOS Configuration Guide - Manual (Page 179)

CanogaOS Configuration Guide
Proprietary & Confidential Canoga Perkins Metro Ethernet Switches Page 179 of 350
Tree Information Base (TIB)
The TIB is the collection of state at a PIM router storing the state of all multicast distribution
trees at that router. It is created by receiving Join/Prune messages, Assert messages, and IGMP
information from local hosts.
Upstream
Towards the root of the tree. The root of the tree might be either the Source or the RP.
Downstream
Away from the root of the tree. The root of tree might be either the Source or the RP.
Source-Based Trees
In the Source-Based Trees concept, the forwarding paths are based on the shortest unicast path to
the source. If the unicast routing metric is hop counts, the branches of the multicast
Source-Based Trees are minimum hop. If the metric is delay, the branches are minimum delay.
For every multicast source, there is a corresponding multicast tree that directly connects the
source to all receivers. All traffic to the members of an associated group passes along the tree
made for their source. Source-Based Trees have two entries with a list of outgoing interfaces--
the source address and the multicast group.
Shared Trees
Shared trees or RP trees (RPT) rely on a central router called the Rendezvous Point (RP) that
receives all traffic from the sources, and forwards that traffic to the receivers. All hosts might not
be receivers. There is a single tree for each multicast group, regardless of the number of sources.
Only the routers on the tree know about the group, and information is sent only to interested
receivers. With an RP, receivers have a place to join, even if no source exists.
The shared tree is unidirectional, and information flows only from the RP to the receivers. If a
host other than the RP has to send data on the tree, the data must first be tunneled to the RP, and
then multicast to the members. This means that even if a receiver is also a source, it can only use
the tree to receive packets from the RP, and not to send packets to the RP (unless the source is
located between the RP and the receivers).
Bootstrap Router (BSR)
When a new multicast sender starts sending data packets, or a new receiver starts sending the
Join message towards the RP for that multicast group, it needs to know the next-hop router
towards the RP. The BSR provides group-to-RP mapping information to all the PIM routers in a
domain, allowing them to map to the correct RP address.