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DVMRP
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Dense-mode-only protocol that uses the flood-and-prune or implicit join
method to deliver traffic everywhere and then determine where the uninterested
receivers are. DVRMP uses source-based distribution trees in the form (S,G)
and builds its own multicast routing tables for RPF checks.
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Not appropriate for large-scale Internet use.
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PIM dense mode
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Sends an implicit join message, so routers use
the flood-and-prune method to deliver traffic everywhere and then determine
where the uninterested receivers are.
PIM dense mode uses source-based distribution trees in the form (S,G),
and also supports sparse-dense mode, with mixed sparse and dense groups. Both
PIM modes use unicast routing information for RPF checks.
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Most promising multicast protocol in use for LANs.
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PIM sparse mode
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Sends an explicit join message, so routers determine
where the interested receivers are and send join messages upstream to their
neighbors, building trees from receivers to a rendezvous point (RP) router,
which is the initial source of multicast group traffic.
PIM sparse mode builds distribution trees in the form (*,G), but migrates
to an (S,G) source-based tree if that path is shorter than the path through
the RP router for a particular multicast group's traffic. Both PIM modes use
unicast routing information for RPF checks.
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Most promising multicast protocol in use for WANs.
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PIM source-specific multicast (SSM)
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Enhancement to PIM sparse mode that allows a client to receive multicast
traffic directly from the source, without the help of a rendezvous point (RP).
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Used with IGMPv3 to create a shortest-path tree between receiver and
source.
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IGMPv1
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The original protocol defined in RFC 1112, Host Extensions
for IP Multicasting. IGMPv1 sends an explicit join message to the
router, but uses a time-out to determine when hosts leave a group.
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IGMPv2
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Defined in RFC 2236, Internet Group Management Protocol, Version
2. Among other features, IGMPv2 adds an explicit leave message
to the join message.
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Used by default.
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IGMPv3
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Defined in RFC 3376, Internet Group Management Protocol, Version
3. Among other features, IGMPv3 optimizes support for a single
source of content for a multicast group, or source-specific multicast
(SSM).
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Used with PIM SSM to create a shortest-path tree between receiver and
source.
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BSR
Auto-RP
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Allow sparse-mode routing protocols to find rendezvous points (RPs)
within the routing domain (autonomous system, or AS). RP addresses can also
be statically configured.
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MSDP
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Allows groups located in one multicast routing domain to find rendezvous
points (RPs) in other routing domains. MSDP is not used on an RP if all receivers
and sources are located in the same routing domain.
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Typically runs on the same router as PIM sparse mode rendezvous point
(RP).
Not appropriate if all receivers and sources are located in the same
routing domain.
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SAP and SDP
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Display multicast session names and correlate the names with multicast
traffic. SDP is a session directory protocol that advertises multimedia conference
sessions and communicates setup information to participants who want to join
the session. A client commonly uses SDP to announce a conference session by
periodically multicasting an announcement packet to a well-known multicast
address and port using SAP.
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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. PGM allows a receiver to detect missing information in all cases
and request replacement information if the receiver application requires it.
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