port
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... restrict multicast traffic, in switched networks, to those ports that
want to receive the multicast traffic. It dynamically establishes
...
... Snooping
can not restrict multicast traffic to ports where at least one
multicast router is connected. It must instead flood ...
... multicast router is connected. It must instead flood multicast
traffic to these ports. Snooping on IGMP messages alone is an
...
... IGMP which traffic flows need to be received by router ports
to be routed because routers do not report these flows ...
... RGMP protocol described in this document restricts multicast
traffic to router ports. To effectively restrict traffic, it must be
supported by both the switches ...
... for switches to expect RGMP messages from only one source per port.
For this reason, RGMP only supports a single RGMP ...
... RGMP to learn which groups are desired at each
of their ports. Multicast routers use RGMP to pass such information
...
... network consumes RGMP messages
received from ports of the network and processes them as described
below. If enabled for RGMP ...
... port upon receipt of an RGMP Hello message on the port, and a
timer [5 * Hello Interval] is started. This timer ...
... removed by the arrival of an RGMP Bye message, then the
port reverts to its prior state of multicast traffic forwarding.
...
... port on a switch that supports RGMP. The port on the
switch MAY want to keep track of the IPv4 ...
... address of the
RGMP Hello and Bye messages it receives on that port. In the event
it receives multiple IPv4 originating addresses ...
... groups 224.0.0.x (x=0...255), 224.0.1.39 and
224.0.1.40, RGMP enabled ports always need to receive traffic for
these groups ...
... Join and Leave messages are accepted if they arrive on an RGMP
enabled port, otherwise they will be discarded. Upon acceptance of
an RGMP Join message ...
... switch SHOULD stop forwarding traffic for the group to that port.
The switch's ability to stop forwarding traffic ...
... switch needs to flood multicast traffic to all ports. If a switch
does actually run one or more mechanisms beside RGMP ...
... flood IPv4 multicast traffic to all ports anymore. Instead,
the switch will try to determine which ports ...
... ports anymore. Instead,
the switch will try to determine which ports still needs to receive
all IPv4 multicast traffic ...
... all IPv4 multicast traffic by default, and which ports do not.
Compliance with this specification requires that a switch ...
... Compliance with this specification requires that a switch MUST be
able to elect a port for flooding through the presence of PIM Hello
...
... PIM Hello
messages [4] arriving from the port and also through a manual
configuration option. In addition, the switch SHOULD recognize a
...
... manual
configuration option. In addition, the switch SHOULD recognize a
port connected to a router by other appropriate protocol packets or
dedicated IPv4 ...
... multicast traffic restriction may also be
used on RGMP enabled ports. In this case, forwarding for a group on
the port ...
... ports. In this case, forwarding for a group on
the port must be established if either mechanism requires it, and it
must only be removed if no mechanism requires it anymore.
...
... inter-switch link and thus the
switch on the other end will only recognize the port as a router port
...
... switch on the other end will only recognize the port as a router port
via the PIM Hello messages flooded by the switches ...
... If appropriate, a switch can send out RGMP messages on ports to make
it look like an RGMP enabled router ...
... switch only affect the state of
their ingress ports, the traffic restriction is applied there only.
RGMP ...
... RGMP means that physical measures will
ensure that such ports are dedicatedly connected to one system which
acts as an RGMP capable router ...
... DoS attacks arise from forged RGMP messages. If more
than one system is connected to a port of the RGMP switch, then one
...
... system may forge RGMP messages and affect the operations of the other
system(s) on the same port. This is a potential security risk.
...
... security ensures that only one system is connected to a
RGMP capable port on a switch, then forged messages from this system
...
... non-RGMP enabled router on the same port. This effectively
introduces a blackholing DoS attack.
...
... multicast traffic
for individual groups toward the port. The effect is a possible
blackholing DoS attack similar to an RGMP ...
... groups indicated in the forged messages. It will also only
affect a port if there officially is only one RGMP enabled router
...
...
A forged RGMP Bye message can turn the port into being
RGMP-disabled. This could, indirectly, cause a DoS attack ...
... RGMP-disabled. This could, indirectly, cause a DoS attack based
on the port getting overloaded with IPv4 multicast traffic ...
... multicast traffic if the
network bandwidth of the port was provisioned with the expectation
that RGMP will suppress unwanted IPv4 ...
...
This type of DoS attack simply re-establishes a port behavior as
if RGMP was not configured and invalidates the benefit of RGMP ...
... RGMP Join message could attract undesired multicast
packets to the port where it is received from. The effect is
similar to an RGMP Bye Message except that it does not affect all
...
... multicast traffic only the groups indicated in the forged
messages. The message will affect a port only if there officially
is only one RGMP enabled router ...
... multicast traffic towards router
ports. This appendix will explain the motivation not to rely on
GARP/GMRP ...
... host/router) on a switch
port which is one reason for its complexity. In RGMP, this
configuration is explicitly not supported: More than one router ...
... configuration is explicitly not supported: More than one router
per switched port is not only not a common scenario in today's
switches layer 2 ...
...
o Support for multiple routers per port
As discussed in Appendix B. This is probably one extension that
...
... should be avoided. Multiple RGMP router per port are
inappropriate for efficient multicast traffic constrainment.
...