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administrative scoping
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Multicast routing strategy that limits the routers and interfaces used
to forward a multicast packet by reserving a range of multicast addresses.
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Auto-RP
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Cisco multicast routing protocol that allows sparse-mode routing protocols
to find rendezvous points (RPs) within a routing domain.
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bootstrap router (BSR)
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Multicast mechanism that allows routers running PIM sparse mode to find
rendezvous points (RPs) within a routing domain.
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branch
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Part of a multicast network that is formed when a leaf subnetwork is
joined to the multicast distribution tree. Branches with no interested receivers
are pruned from the tree so that multicast packets are no longer replicated
on the branch.
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broadcast routing protocol
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Protocol that distributes traffic from a particular source to all destinations.
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dense mode
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Multicast routing mode appropriate for LANs with many interested receivers.
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Designated Router (DR)
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Router on a subnet that is selected to control multicast routes for
the sources and receivers on the subnet. When more than one multicast-enabled
router is located on a subnet, the selected DR is the router with the highest
priority. If the DR priorities match, the router with the highest IP address
is selected as the DR.
The source’s DR sends PIM register messages from the source network
to the rendezvous point (RP). The receiver’s DR sends PIM join and PIM
prune messages from the receiver network toward the RP.
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Distance Vector Multicast Routing Protocol (DVMRP)
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Distributed multicast routing protocol that dynamically generates IP
multicast distribution trees using reverse-path multicasting (RPM) to forward
multicast traffic to downstream interfaces.
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distribution tree
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Path linking multicast receivers (listeners) to sources. The root of
the tree is at the source, and the branches connect subnetworks of interested
receivers (leaves). Multicast packets are replicated only where a distribution
tree branches. To shorten paths to a source at the edge of a network, sparse
mode multicast protocols can use a shared distribution
tree located more centrally in the network backbone.
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downstream interface
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Interface on a multicast router that is leading toward the receivers.
You can configure all the logical interfaces except one as downstream interfaces.
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group address
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Multicast destination address. A multicast network uses the Class D
IP address of a logical group of multicast receivers to identify a destination.
IP multicast packets have a multicast group address as the destination address
and a unicast source address.
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Internet Group Management Protocol (IGMP)
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Multicast routing protocol that runs between receiver hosts and routers
to determine whether group members are present. Services Routers support IGMPv1,
IGMPv2, and IGMPv3.
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leaf
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IP subnetwork that is connected to a multicast router and that includes
at least one host interested in receiving IP multicast packets. The router
must send a copy of its multicast packets out on each interface with a leaf,
and its action is unaffected by the number of leaves on the interface.
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listener
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Another name for a receiver in a multicast network.
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multicast routing protocol
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Protocol that distributes traffic from a particular source to only the
destinations needing to receive it. Typical multicast routing protocols are
the Distance Vector Multicast Routing Protocol (DVMRP) and Protocol Independent
Multicast (PIM).
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Multicast Source Discovery Protocol (MSDP)
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Multicast routing protocol that connects multicast routing domains and
allows them to find rendezvous points (RPs).
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Pragmatic General Multicast (PGM)
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Special protocol layer for multicast traffic that can be used between
the IP layer and the multicast application to add reliability to multicast
traffic.
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Protocol Independent Multicast (PIM) protocol
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Protocol-independent multicast routing protocol that can be used in
either sparse or dense mode. In sparse mode, PIM routes to multicast groups
that might span WANs and interdomain Internets. In dense mode, PIM is a flood-and-prune
protocol.
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pruning
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Removing from a multicast distribution tree branches that no longer
include subnetworks with interested hosts. Pruning ensures that packets are
replicated only as needed.
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reverse-path forwarding (RPF)
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Multicast routing strategy that allows a router to receive packets through
an interface if it is the same interface a unicast packet uses as the shortest
path back to the source.
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rendezvous point (RP)
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Core router operating as the root of a shared distribution tree in a
multicast network.
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Session Announcement Protocol (SAP)
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Multicast routing protocol used with other multicast protocols—typically
Session Description Protocol (SDP)—to handle session conference announcements.
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Session Description Protocol (SDP)
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Session directory protocol that advertise multimedia conference sessions
and communicates setup information to participants who want to join the session.
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shortest-path tree (SPT)
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Multicast routing strategy for sparse mode multicast protocols. SPT
uses a shared distribution tree rooted in the network backbone to shorten
paths to sources at the edge of a network.
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source-specific multicast (SSM)
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Service that allows a client to receive multicast traffic directly from
the source, without the help of a rendezvous point (RP).
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sparse mode
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Multicast routing mode appropriate for WANs with few interested receivers.
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unicast routing protocol
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Protocol that distributes traffic from one source to one destination.
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upstream interface
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Interface on a multicast router that is leading toward the source. To
minimize bandwidth use, configure only one upstream interface on a router
receiving multicast packets.
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