D-Link DGS-3630 Series Reference Manual page 308

DGS-3630 Series Layer 3 Stackable Managed Switch Web UI Reference Guide
PIM-DM
The Protocol Independent Multicast - Dense Mode (PIM-DM) protocol should be used in networks with a low delay
(low latency) and high bandwidth, as PIM-DM is optimized to guarantee delivery of multicast packets and not to
reduce overhead.
The PIM-DM multicast routing protocol is assumes that all downstream routers want to receive multicast messages
and relies upon explicit prune messages from downstream routers to remove branches from the multicast delivery tree
that do not contain multicast group members.
PIM-DM has no explicit Join messages. It relies upon periodic flooding of multicast messages to all interfaces and
then either waiting for a timer to expire (the Join/Prune Interval), or for the downstream routers to transmit explicit
Prune messages indicating that there are no multicast members on their respective branches. PIM-DM then removes
these branches (Prunes them) from the multicast delivery tree.
As a member of a pruned branch of a multicast delivery tree may want to join a multicast delivery group (at some point
in the future), the protocol periodically removes the 'prune' information from its database and floods multicast
messages to all interfaces on that branch. The interval for removing 'prune' information is the Join/Prune Interval.
PIM-SM-DM
In the PIM-SM, RP is a key point for the first hop of the sender. If the first hop does not have RP information when the
sender sends information out, it will drop the packet and do nothing. Sparse-Dense mode will be useful in this
condition. In Sparse-Dense mode, the packets can be flooded to all the outgoing interfaces and pruning/joining
(Prune/Graft) can be used to control the outgoing interface list if RP is not found. In other words, the PIM Sparse-
Dense mode is treated in either the sparse mode or dense mode of the operation; it depends on which mode the
multicast group operates. When an interface receives multicast traffic, if there is a known RP for the group, then the
current operation mode on the interface is sparse mode, otherwise the current operation mode on the interface will be
dense mode.
PIM for IPv4
PIM Interface
This window is used to display and configure the Protocol Independent Multicast (PIM) interface settings.
To view the following window, click L3 Features > IP Multicast Routing Protocol > PIM > PIM for IPv4 > PIM
Interface, as shown below:
The fields that can be configured are described below:
Parameter
Interface Name
Mode
Click the Find button to locate a specific entry based on the information entered.
Click the Show All button to display all the entries.
Figure 6-116 PIM Interface Window
Description
Select and enter the name of the interface here.
Select the operation mode of PIM entries used in this filtered search here. Options
to choose from are Dense Mode, Sparse Mode, and Sparse-Dense Mode.
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