multicast
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... IP
destination address. A multicast datagram is delivered to all
members of its destination host ...
... group, that is permanent; at any time a
permanent group may have any number of members, even zero. Those IP
multicast addresses that are not reserved for permanent groups are
...
... as long as they have members.
Internetwork forwarding of IP multicast datagrams is handled by
"multicast routers ...
... IP multicast datagrams is handled by
"multicast routers" which may be co-resident with, or separate from,
internet gateways ...
... datagram as a
local network multicast which reaches all immediately-neighboring
members of the destination host group ...
... IP
time-to-live greater than 1, the multicast router(s) attached to the
local network take responsibility for forwarding it towards all other
...
... transmitting the
datagram as a local multicast.
This memo specifies the extensions required of a host ...
... internet host or gateway other than those acting as multicast
routers. The algorithms and protocols used within and between
multicast routers ...
... multicast
routers. The algorithms and protocols used within and between
multicast routers are transparent to hosts and will be specified in
separate documents. This memo also does not specify how local
...
... IP multicasting. Level 0 hosts will, in general, be
unaffected by multicast activity. The only exception arises on some
types of local network, where the presence of level 1 or 2 hosts ...
... network, where the presence of level 1 or 2 hosts may
cause misdelivery of multicast IP datagrams to level 0 hosts. Such
...
...
Level 1 allows a host to partake of some multicast-based services,
such as resource location or status reporting, but it does not allow
...
... hosts. This is used to address all
multicast hosts on the directly connected network. There is no
...
... hosts on the directly connected network. There is no
multicast address (or any other IP address) for all hosts on the
...
... host IP implementation must
support the transmission of multicast IP datagrams. To support level
2 IP multicasting ...
... IP multicasting, a host must also support the reception of
multicast IP datagrams. Each of these two new services is described
...
... SENDING MULTICAST IP DATAGRAMS ...
... protocol to specify the IP time-to-live of an outgoing multicast
datagram, if such a capability does not already exist. If the
...
... upper-layer protocol chooses not to specify a time-to-live, it should
default to 1 for all multicast IP datagrams, so that an explicit
choice is required to multicast ...
... multicast IP datagrams, so that an explicit
choice is required to multicast beyond a single network.
...
... upper-layer protocol
to identify which network interface is be used for the multicast
transmission. Only one interface is used for the initial
...
... transmission. Only one interface is used for the initial
transmission; multicast routers are responsible for forwarding to any
other networks, if necessary. If the upper-layer ...
... network service interface is required to
support the sending of multicast IP datagrams. The IP module merely
...
...
The Ethernet directly supports the sending of local multicast packets
by allowing multicast addresses in the destination ...
... Ethernet directly supports the sending of local multicast packets
by allowing multicast addresses in the destination field of Ethernet
packets. All that is needed to support the sending of multicast ...
... multicast addresses in the destination field of Ethernet
packets. All that is needed to support the sending of multicast IP
datagrams is a procedure for mapping IP host ...
... host group address is mapped to an Ethernet multicast address
by placing the low-order 23-bits of the IP address ...
... 23 bits of the Ethernet multicast address 01-00-5E-00-00-00 (hex).
Because there are 28 significant bits in an IP ...
... IEEE 802.2 standard, may be handled the same
way as Ethernet for the purpose of sending multicast IP datagrams.
For a network ...
... host and a multicast router), multicasts should be transmitted
exactly like unicasts. For a store-and-forward network ...
... be mapped to the well-known local address of an IP multicast router;
a router on such a network ...
... router on such a network would take responsibility for completing
multicast delivery within the network as well as among networks ...
... interface unspecified, in which case the request
will apply to the default interface for sending multicast datagrams
(see section 6.1).
...
... group on more than one interface,
in which case duplicate multicast datagrams may be received. It is
also permissible for more than one upper-layer ...
... interface, the datagram is quietly discarded.
(These cases should occur only as a result of inadequate multicast
address filtering in a local network module.)
...
... interface is notified, so that it may update its multicast reception
filter (see section 7.3).
...
... IGMP protocol,
specified in Appendix I. IGMP is used to keep neighboring multicast
routers informed of the host group memberships present on a
...
... hosts group are recognized as a
special case by the multicast routers and are never forwarded beyond
a single network, regardless of their time-to-live ...
...
Incoming local network multicast packets are delivered to the IP
module using the same "Receive Local" operation as local network ...
... IP module to tell the local network
module which multicast packets to accept, the local network service
interface ...
...
The local network module must not deliver up any multicast packets
that were transmitted from that module; loopback of multicasts ...
... multicast packets
that were transmitted from that module; loopback of multicasts is
handled at the IP layer or higher.
...
... module must be able to receive packets addressed to the Ethernet
multicast addresses that correspond to the host's IP host ...
...
listening on an arbitrary number of Ethernet multicast addresses,
which may mean "opening up" the address filter ...
... address filter to accept all
multicast packets during those periods when the number of addresses
exceeds the limit of the filter ...
... the same way as Ethernet for the purpose of receiving multicast IP
datagrams. For pure broadcast networks ...
... point-to-point or
store-and-forward networks, multicast IP datagrams will arrive as
local network ...
... host group memberships to any immediately-neighboring
multicast routers. IGMP is an asymmetric protocol and is specified
here from the point of view of a host ...
... IGMP is an asymmetric protocol and is specified
here from the point of view of a host, rather than a multicast
router. (IGMP may also be used, symmetrically or asymmetrically,
between multicast routers ...
... multicast
router. (IGMP may also be used, symmetrically or asymmetrically,
between multicast routers. Such use is not specified here.)
Like ICMP ...
... host whose delay timer expires first.
Note that the multicast routers receive all IP multicast
datagrams ...
... timer expires first.
Note that the multicast routers receive all IP multicast
datagrams, and therefore need not be addressed explicitly.
...
... routers assume that that group has no local members and
that they need not forward remotely-originated multicasts for that
group onto the local network ...
... hosts
and networks very low. However, when a multicast router starts up,
it may issue several closely-space Queries ...
... bound to a set of IP unicast addresses. The multicast routers do not
need to maintain a list of individual members of each host group ...
... host group.
For example, a multicast router attached to an Ethernet need
associate only a single Ethernet ...
... group addresses have been defined specifically for use in the
destination address field of multicast IP datagrams. However, the
fact that group addresses ...
... group addresses
are mapped to Ethernet multicast addresses. A portion of the IP
group address space may be set aside for random allocation by
...
... address space may be set aside for random allocation by
applications that can tolerate occasional collisions with other
multicast users, perhaps generating new addresses until a suitably
"quiet" one is found.
...
...
The IP multicast extensions specified in this memo are significantly
different from those specified in RFC-988(-> 1112std5 | 1054(-> 1112std5)). Most of the changes are
...
... different from those specified in RFC-988(-> 1112std5 | 1054(-> 1112std5)). Most of the changes are
due to a shift of responsibility away from the multicast routers
(called "multicast agents ...
... due to a shift of responsibility away from the multicast routers
(called "multicast agents" in RFC-988(-> 1112std5 | 1054(-> 1112std5))) and onto the hosts ...
... gateway architecture of the Internet, and it allows the IP
multicast services (in the same way as the IP unicast services ...
... IP broadcast
applications may be migrated to the use of IP multicast before
multicast routers are widely available. The following changes are a
...
... applications may be migrated to the use of IP multicast before
multicast routers are widely available. The following changes are a
consequence of this shift of responsibility:
...
... hosts groups and access keys have been eliminated.
The multicast routers are no longer considered trustworthy
controllers of group membership; it is up to hosts ...
... end-to-end encryption or by imposing restrictions on the
flow of IP multicast datagrams into and out of particular
administrative domains ...
... host groups has been
moved from multicast routers to the hosts. See Appendix II
for a brief discussion ...
... non-blocking, because it is no longer necessary to await
approval from a multicast router when changing membership. It
is also no longer possible for a host to have its membership
...
... is also no longer possible for a host to have its membership
revoked by a multicast router.
- The IGMP ...
... 988(-> 1112std5 | 1054(-> 1112std5)), reflecting the changed roles of hosts and multicast
routers.
- The new IGMP ...
... are:
- The decision whether or not to loop back a multicast datagram
sent from a member of the destination ...