D-Link DI-1750 Reference Manual page 300

1. IGMP
IGMP is a class protocol which aim at multicast group member management,IGMP is short for Internet
Group Management Protocol.IGMP is a anisomerous protocol,it consist host and router.The protocol of
the host part regulate host how to report its own identity to the route and host how to respond to the
Query message send by the router. The protocol of the router part regulate router which support IGMP
how to obtain the host's group member identity in local network, and according to the report send by the
host update group member's information which is saved by the router.
According to implement of IGMP router part protocol in our routers,it can provide the exist of present
network multicast-group member to the multicast route protocol of the router. The protocol will
determine whether to transmit multicast message. Generally speaking, in order to make our router
support IP message multicast process, it need to implement multicast route protocol and IGMP router
part protocol. Present, our router has implement IGMP router part protocol, which support the newest
version—IGMP version 3.
In the actual implement, there is no sole start command which is aim at IGMP, IGMP router port
function start from Multicast Routing Protocol.
2. OLNK
Strictly speaking, OLNK（IGMP only-link）could not be called multicast-group route protocol, because it
can't provide interaction of protocol. But, run OLNK will obtain good effort under some specified
situation and simple topology environment. It is similar to PIM-DM which couldn't provide interaction of
protocol., and it can manage local IGMP group member's change, according to topology change adjust
RPF interface, it will not only ensure the transmit of multi-cast , but also avoid the control message of
multi-cast route protocol occupy the usage of bandwidth,
3. PIM-DM
PIM-DM(Protocol Independent Multicast Dense Mode) is a kind of multi-cast route protocol with
compression mode, default considering, when multi-cast begin to send multi-cast data, network
stations from the whole work place have to receive the data, so the PIM-DM will choose the
diffuse-pruning to transmit the multi-cast data. When multi-cast source begin to transmit the data, the
interface active by PIM along with router face to the RPF interface of the source will transmit the
multi-cast data package. In this way, all network nodes of PIM-DM area will receive those multi-cast
data package. In order to complete the multi-cast transmit, relative routers should create the multi-cast
router item (s,g) for group G and its source S.(S,G) includes the source address , group address, entry
address, exit address, timer and flags of multi-cast.
If there is no multi-cast member in some area in network, PIM-DM protocol will send pruning message,
it will pruning at the transmit interface via the area and will build the pruning states which corresponding
the overtime times. When the times overtime, the pruning states will return to transmit states again, and
the multi-cast data will down along the branch again. Besides, pruning states includes multi-cast source
and multi-cast group message. When the multi-cast group member happen in pruning area ,in order to
reduce the response time ,protocol
Model Name
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