multicast
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... V6MISSUES], there exists a deployment problem
with global, interdomain IPv6 multicast: PIM-SM [PIM-SM] RPs have no
...
... PIM-SM] RPs have no
way of communicating the information about (active) multicast sources
to other multicast domains, as Multicast Source Discovery Protocol ...
... active) multicast sources
to other multicast domains, as Multicast Source Discovery Protocol
(MSDP ...
... multicast sources
to other multicast domains, as Multicast Source Discovery Protocol
(MSDP) [MSDP ...
... MSDP] has deliberately not been specified for IPv6.
Therefore the whole interdomain Any Source Multicast (ASM) model is
rendered unusable; Source-Specific Multicast ...
... Any Source Multicast (ASM) model is
rendered unusable; Source-Specific Multicast (SSM) [SSM] avoids these
...
... it seems unlikely that SSM could be usable as the only interdomain
multicast routing mechanism in the short term.
...
... the address of the RP is encoded in the IPv6 multicast group address,
and specifies a PIM-SM ...
... This mechanism not only provides a simple solution for IPv6
interdomain Any Source Multicast but can be used as a simple solution
for IPv6 intra-domain ...
... IPv6 intra-domain ASM with scoped multicast addresses as well.
It can also be used as an automatic RP ...
...
o A specification of a subrange of [RFC3306] IPv6 multicast group
addresses defined by setting one previously unused bit of the
...
... MSDP, and the routers are not
required to include any multicast configuration, except when they act
as an RP.
...
... used.
The assignment of multicast addresses is outside the scope of this
document; it is up to the RP and applications to ensure that group
addresses ...
... domain to the information distribution. However, as it gives a
solution for the global IPv6 multicast Internet, spanning multiple
administrative domains ...
... Internet, spanning multiple
administrative domains, we say it is a solution for inter-domain
multicast.
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
...
... Interior Gateway Protocol
MLD Multicast Listener Discovery
MSDP Multicast Source Discovery Protocol ...
... Multicast Listener Discovery
MSDP Multicast Source Discovery Protocol
PIM Protocol Independent Multicast ...
... Multicast Source Discovery Protocol
PIM Protocol Independent Multicast
PIM-SM Protocol Independent Multicast ...
...
As described in [RFC3306], the multicast address format is as
follows:
...
...
When the highest-order bit is 0, R = 1 indicates a multicast address
that embeds the address on the RP ...
... addresses.
That is, to identify whether it is a multicast address as specified
in this memo and to be processed any further, an address must satisfy
...
... all of the following:
o It MUST be a multicast address with "flgs" set to 0111, that is, to
be of the prefix FF70::/12,
...
... The address of the RP can be obtained from a multicast address
satisfying the above criteria by taking the following two steps:
...
... network prefix field SHOULD be zero" is ignored. This is
to allow multicast group address allocations to be consistent with
unicast prefixes ...
... unicast prefixes; the multicast addresses would still use the RP
associated with the network ...
... "plen" higher than 64 MUST NOT be used, as that would overlap with
the high-order bits of multicast group-id.
When processing an encoding ...
... encoding to get the RP address, the multicast
routers MUST perform at least the same address validity checks to the
...
... address would
be "2001:DB8:BEEF:FEED::y". There are still 32 bits of multicast
group-ids to assign to customers and self ("y" could be anything from
1 to F, as 0 must not be used).
...
... specific part of the unicast prefix, with plen=32, and the group
addresses will be from the multicast prefix:
...
...
As in Example 2, the network administrator can also assign multicast
prefixes such as "FF7x:y20:2001:DB8:DEAD::/80" to some of customers ...
... this is just a more specific subcase of Example 2, where the
administrator assigns a multicast prefix, not just individual group-
...
... RP address: the "plen" field in
the multicast address, 0x20 = 32, refers to the length of "network
prefix ...
... are preserved: the value of "plen" takes no stance on actual
unicast/multicast prefix lengths allocated or used in the networks,
...
... own PIM-SM domain. The organization can pick multicast addresses
such as "FF7x:y30:2001:DB8:BEEF::/80", and then the RP address ...
... domain to
share an address and multicast state information between a set of RPs
mainly for redundancy ...
... MSDP, each
Designated Router connecting multicast sources could act as an RP
without scalability ...
... RP failover mechanisms: if the DR goes
down, the multicast transmission may not work anymore in any case.
Along the same lines, its may also be desirable to distribute the RP ...
... group address. For proper
protection, one should set up, for example, PIM multicast scoping
borders at the border routers. Therefore, embedded-RP ...
... Join process towards
the RP encoded in the multicast address, irrespective of whether
it is in the "local" or "remote" PIM domain ...
... administrator for group assignment or
using a multicast address assignment protocol).
2. The sender ...
... receivers or senders are
located. Hence, the inter-domain multicast becomes a flat, RP-
centered topology ...
... for the specific group. This is especially important with large
multicast groups where there are a lot of heavy senders --
particularly if implementations do not handle unicast ...
... inter-domain model, this specification
simplifies the tree construction (i.e., multicast routing) by
removing the RP ...
... though rare), with this specification the hosts and users using
multicast indirectly specify the RP themselves, lowering the
expectancy of the RP ...
... reachability. This is a relatively significant
problem but not much different from the current multicast deployment:
e.g., MLDv2 ...
...
A more extensive description and comparison of the inter-domain
multicast routing models (traditional ASM with MSDP, embedded-RP ...
...
The addresses of RPs are encoded in the multicast addresses, thus
becoming more visible as single points of failure. Even though this
does not significantly affect the multicast routing ...
... multicast addresses, thus
becoming more visible as single points of failure. Even though this
does not significantly affect the multicast routing security, it may
expose the RP ...
... scenario. However, this can be mitigated, as the RP can discard all
such messages for all multicast addresses that do not encode the
address of the RP ...
...
Additionally, the implementation SHOULD also allow manual
configuration of which multicast prefixes are allowed to be used.
This can be used to limit the use of the RP ...
... router could potentially become an RP (and be abused
as such). Further, multicast groups or group ranges to-be-served MAY
...
...
A more extensive description and comparison of the inter-domain
multicast routing models (traditional ASM with MSDP, embedded-RP ...
... Haberman, B. and D. Thaler, "Unicast-Prefix-based IPv6 Multicast Addresses", RFC 3306prop, August 2002. ...
... Anycast Rendevous Point (RP) mechanism using Protocol Independent Multicast (PIM) and Multicast Source Discovery Protocol (MSDP ...
... using Protocol Independent Multicast (PIM) and Multicast Source Discovery Protocol (MSDP)", RFC 3446, January 2003. ...
... Fenner, B. and D. Meyer, "Multicast Source Discovery Protocol (MSDP)", RFC 3618exp, October 2003. ...
... Savola, P., Lehtonen, R., and D. Meyer, "PIM-SM Multicast Routing Security Issues and Enhancements", Work in Progress, October 2004. ...
... Fenner, B. et al, "Protocol Independent Multicast - Sparse Mode (PIM-SM): Protocol Specification ...
... Values 64 < "plen" < 96 would overlap with upper bits of the
multicast group-id; due to this restriction, "plen" must not exceed
64 bits. This is in line with RFC 3306prop ...
... encoded in the RP address somehow, or in the multicast group address.
In any case, such modifications are beyond the scope of this memo.
...