address
Click on the red underlined text to get to the source
... This memo describes a multicast address allocation policy in which
the address of the RP is encoded in the IPv6 multicast group address ...
... address of the RP is encoded in the IPv6 multicast group address,
and specifies a PIM-SM group ...
... 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
Flags field ...
... Flags field to "1",
o a specification of the mapping by which such a group address
encodes the RP address ...
... Addresses in the subrange will be called embedded-RP addresses.
This scheme obviates the need for MSDP ...
... RP address can't be embedded into a 128-bit group address
with space left to carry the group identity ...
... 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 ...
... multicast addresses is outside the scope of this
document; it is up to the RP and applications to ensure that group
addresses are unique by using some unspecified method. However, the
mechanisms are probably similar to those used with [RFC3306 ...
...
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 ...
... bit is 0, R = 1 indicates a multicast address
that embeds the address on the RP. Then P MUST be set to 1, and
consequently T MUST be set to 1, as specified in [RFC3306 ...
...
R = 0 indicates a multicast address that does not embed the address
of the RP and follows the semantics ...
... 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
...
... 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:
...
... 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,
...
... o "plen" MUST NOT be greater than 64.
The address of the RP can be obtained from a multicast address
...
... 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 ...
... When processing an encoding to get the RP address, the multicast
routers MUST perform at least the same address validity ...
... RP address, the multicast
routers MUST perform at least the same address validity checks to the
calculated RP ...
... validity checks to the
calculated RP address as to one received via other means (like BSR
[BSR ...
... RIID=0 is reserved, see section 6.3). However, each of these
is an IPv6 group address of its own (i.e., there can be only one RP
per multicast address ...
... subnet, e.g., 2001:DB8:BEEF:FEED::/64.
In that case, the group addresses would be something like
"FF7x:y40:2001:DB8:BEEF:FEED::/96", and then their RP address ...
... group addresses would be something like
"FF7x:y40:2001:DB8:BEEF:FEED::/96", and then their RP address would
be "2001:DB8:BEEF:FEED::y". There are still 32 bits of multicast
group ...
... RP but, to make it more flexible, wants to place it on a
specifically routed subnet and wants to keep larger address space for
group allocations. That is, the administrator ...
... administrator selects the least
specific part of the unicast prefix, with plen=32, and the group
addresses will be from the multicast prefix:
...
... router as a loopback
address and is injected into the routing system; if the network
administrator sets up only one or two RPs (and, e.g., not one RP ...
... customers.
In this case the RP address would still be "2001:DB8::y". (Note that
this is just a more specific subcase of Example 2, where the
administrator ...
...
Note the second rule of deriving the RP address: the "plen" field in
the multicast address, 0x20 = 32, refers to the length of "network ...
... RP address: the "plen" field in
the multicast address, 0x20 = 32, refers to the length of "network
prefix ...
... prefix" field considered when obtaining the RP address. In this
case, only the first 32 bits of the network ...
...
In short, this distinction allows more flexible RP address
configuration in the scenarios where it is desirable to have the
group addresses be consistent with the unicast prefix ...
... RP address
configuration in the scenarios where it is desirable to have the
group addresses be consistent with the unicast prefix allocations.
...
... network of Examples 1, 2, and 3, the network admin sets up
addresses for use by customers, but an organization wants to have its
own PIM-SM ...
... own PIM-SM domain. The organization can pick multicast addresses
such as "FF7x:y30:2001:DB8:BEEF::/80", and then the RP address ...
... multicast addresses
such as "FF7x:y30:2001:DB8:BEEF::/80", and then the RP address would
be "2001:DB8:BEEF::y".
...
... Guidelines for Assigning IPv6 Addresses to RPs ...
... If an administrator wishes to use an RP address that does not conform
to the addressing topology ...
... unicast prefix (e.g., an additional loopback address assigned on a
router, as described in Example 2 in Section 5.1), that address ...
... address assigned on a
router, as described in Example 2 in Section 5.1), that address can
be injected into the routing system via a host ...
... throughout the PIM domain is not necessary, as each group address
specifies the RP to be used.
...
... Group) or (S,G) Join by
guessing/learning the source and/or the group address. For proper
protection, one should set up, for example, PIM multicast ...
... method.
The implementation will have to recognize the address format and
derive and use the RP address ...
... address format and
derive and use the RP address by using the rules in Section 4. This
information is used at least when performing Reverse Path Forwarding
...
... encapsulation.
To avoid loops and inconsistencies, for addresses in the range
FF70::/12, the Embedded-RP ...
... RP mapping must be
redone for every new IPv6 group address that would map to a different
RP. For efficiency, the results may be cached in an implementation-
...
...
1. A receiver finds out a group address by some means (e.g., SDR or a
web page).
...
... Join process towards
the RP encoded in the multicast address, irrespective of whether
it is in the "local" or "remote" PIM domain ...
...
1. A sender finds out a group address by using an unspecified method
(e.g., by contacting the administrator ...
... administrator for group assignment or
using a multicast address assignment protocol).
2. The sender ...
... PIM-SM Register-messages to the RP address encoded in the
multicast address (in the special case that DR ...
... group-to-RP mapping mechanism. Instead of obtaining
the address of the RP from local configuration or configuration
protocols (e.g., BSR ...
... MSDP information distribution.
As the address of the RP is tied to the multicast address, the RP ...
... The PIM-SM specification states, "Any RP address configured or
learned MUST be a domain-wide reachable address ...
... address configured or
learned MUST be a domain-wide reachable address". What "reachable"
precisely means is not clear, even without embedded-RP. This
...
...
The addresses of RPs are encoded in the multicast addresses, thus
becoming more visible as single points of failure. Even though this
...
...
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 ...
... 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 ...
... such messages for all multicast addresses that do not encode the
address of the RP. Both the sender- and receiver-based ...
... only. In some cases, being able to restrict (at the RP) which
unicast addresses are allowed to send or join to a group is
...
... MSDP information.
The implementation MUST perform at least the same address validity
checks to the embedded-RP ...
... validity
checks to the embedded-RP address as it would to one received via
other means; at least fe80::/10, ::/16, and ff00::/8 should be
excluded. This is particularly important, as the information is
...
... RIID, the value could be pre-determined (e.g., "1"). However, this
has not been adopted, as this eliminates address assignment
flexibility from the operator.
...
... addressing could be used to convey other information
(other than RP address) as well, for example, what should be the RPT
threshold for PIM-SM ...
... PIM-SM. These could be, whether feasible or not,
encoded in the RP address somehow, or in the multicast group address.
In any case, such modifications are beyond the scope of this memo.
...
... encoded in the RP address somehow, or in the multicast group address.
In any case, such modifications are beyond the scope of this memo.
...
... Authors' Addresses ...
... copyrights, patents or patent applications, or other proprietary
rights that may cover technology that may be required to implement
this standard. Please address the information to the IETF at ietf-
ipr@ietf.org.
...