Using Layer 3 Multicast Suppression Protocols Above Layer 3
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Routing
Mobile Ad Hoc Networks [manet]
Mobility
Multicast Suppression
This document specifies how protocols operating at layers above
layer 3 can use the multicast suppression algorithms, for instance
the algorithms specified in RFC 6621.
Limiting the number of multicast forwarders provides performance
benefits when used with a protocol that relies on flooding messages
throughout a network. Some good multicast suppression methods for
limiting the number of multicast forwarders while maintaining complete
network coverage are specified in RFC 6621 .
Routing protocols that use multicast can offer much greater
performance using multicast suppression algorithms. Such algorithms
do not affect the origination of multicast messages, but only determine
whether a node needs to forward incoming multicast messages that are
intended to flood the network. Enabling performance benefits for
reactive manet routing protocols was a strong motivating factor in
the development and publication of RFC 6621.
RFC 6621 multicast suppression algorithms are specified to operate at
layer 3. Manet routing protocols use RFC 5444
as a message bundling layer; they operate above layer 3. Such
protocols specify that incoming multicast control messages have to be
processed before regeneration; in other words, the incoming multicast
message is not forwarded at all.
Manet control messages are sent with the IP destination address
set to the link-local multicast address LL-MANET-Routers
unless otherwise specified.
This document specifies a way to use layer 3 multicast suppression
algorithms at a layer above layer 3 so that algorithms that
require network-wide flooding can reap the benefits of layer-3
multicast suppression algorithms.
This document defines the following terminology:
A node that
currently forwards incoming multicast messages to its neighbors, based on the results of running a multicast suppression
algorithm.
An algorithm
that determines which multicast routers are required for
complete coverage of a multicast group; retransmission by other
multicast routers for the multicast group is unnecessary.
Transmission of a message
formed by processing and modification of an incoming
message for an operation requiring the attention of
members of a multicast group.
If the node is not currently a multicast forwarding node,
then the node does not regenerate multicast messages even
if the conditions for regeneration are satisfied.
For example, if an AODVv2
router is not currently a multicast forwarding node, then it does
not regenerate multicast messages
(e.g., RREQ or RERR) even if the conditions for regeneration are
satisfied. This restriction only applies for regeneration, and does
not apply for multicast RREQ or RERR messages originated by the node.
This document does not introduce any security mechanisms,
and does not have any impact on existing security mechanisms.
This document does not specify any IANA actions.