3com 3031 Instruccion De Instalación
594
C
HAPTER
45: IP M
ULTICAST
IP Multicast Packet
Forwarding
Forwarding
In the multicast model, the source host sends information to the host group
represented by the multicast group address within the destination address fields of
the IP packets. Different from the unicast model, the multicast model must
forward the multicast packets to multiple external interfaces so that the packets
can be sent to all receiving stations. Therefore, the multicast forwarding process is
much more complex than the unicast forwarding process.
represented by the multicast group address within the destination address fields of
the IP packets. Different from the unicast model, the multicast model must
forward the multicast packets to multiple external interfaces so that the packets
can be sent to all receiving stations. Therefore, the multicast forwarding process is
much more complex than the unicast forwarding process.
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RPF (Reverse Path Forwarding)
To ensure that multicast packets reach a router along the shortest path, the
multicast router must check the receiving interface of multicast packets
depending on the unicast routing table or a unicast routing table
independently provided for multicast (such as the MBGP multicast routing
table). This check mechanism is the basis for most multicast routing protocols
to perform multicast forwarding, and is known as RPF (Reverse Path
Forwarding) check. A multicast router uses the source address of a received
multicast packet to query the unicast routing table or the independent
multicast routing table to determine that the receiving interface is on the
shortest path from the receiving station to the source. If a source tree is used,
the source address is the address of the source host sending the multicast
packet. If a shared tree is used, the source address is the RP address of the
shared tree. A multicast packet arriving at the router, will be forwarded
according to the multicast forwarding entry. if it passes the RPF check, or else
will be discarded.
multicast router must check the receiving interface of multicast packets
depending on the unicast routing table or a unicast routing table
independently provided for multicast (such as the MBGP multicast routing
table). This check mechanism is the basis for most multicast routing protocols
to perform multicast forwarding, and is known as RPF (Reverse Path
Forwarding) check. A multicast router uses the source address of a received
multicast packet to query the unicast routing table or the independent
multicast routing table to determine that the receiving interface is on the
shortest path from the receiving station to the source. If a source tree is used,
the source address is the address of the source host sending the multicast
packet. If a shared tree is used, the source address is the RP address of the
shared tree. A multicast packet arriving at the router, will be forwarded
according to the multicast forwarding entry. if it passes the RPF check, or else
will be discarded.
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Multicast policy routing
Multicast policy routing complements the routing table-based packet
forwarding function and allows packets to be forwarded by specified policies.
forwarding function and allows packets to be forwarded by specified policies.
As an extension to unicast ploicy outing, multicast policy routing is
implemented by configuring Route-policy, described by a groupuser-definable
of IF-MATCH-APPLY statements . The IF-MATCH clauses define the matching
rules which when met, the multicast packet will be forwarded according to the
actions configured by the user (described by APPLY clauses) as opposed to the
usual process.
implemented by configuring Route-policy, described by a groupuser-definable
of IF-MATCH-APPLY statements . The IF-MATCH clauses define the matching
rules which when met, the multicast packet will be forwarded according to the
actions configured by the user (described by APPLY clauses) as opposed to the
usual process.
Application of
Multicast
Multicast
IP multicast technology effectively implements -point to multi-point forwarding
with high speed, saving a large amount of network bandwidth and relieving
network loads. It also facilitates the development of new value-added services t in
the Internet information service area that include online live broadcasting, Web TV,
distance education, distance medical treatment, network radio station and
real-time audio/video conferencing.It takes a positive role in:
with high speed, saving a large amount of network bandwidth and relieving
network loads. It also facilitates the development of new value-added services t in
the Internet information service area that include online live broadcasting, Web TV,
distance education, distance medical treatment, network radio station and
real-time audio/video conferencing.It takes a positive role in:
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Multimedia and streaming media applications
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Occasional communication for training and cooperation
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Data storage and finance (stock) operation
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Point-to-multipoint data distribution