D-Link xStack Reference Manual page 250

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xStack DGS-3620 Series Layer 3 Managed Stackable Gigabit Switch Web UI Reference Guide
IGMP Version 3
The current release of the Switch now implements IGMPv3. Improvements of IGMPv3 over version 2 include:
The introduction of the SSM or Source Specific Multicast. In previous versions of IGMP, the host would receive
all packets sent to the multicast group. Now, a host will receive packets only from a specific source or sources. This
is done through the implementation of include and exclude filters used to accept or deny traffic from these specific
sources.
In IGMP v2, Membership reports could contain only one multicast group whereas in v3, these reports can
contain multiple multicast groups and multiple sources within the multicast group.
Leaving a multicast group could only be accomplished using a specific leave message in v2. In v3, leaving a
multicast group is done through a Membership report, which includes a block message in the group report packet.
For version 2, the host could respond to a group query but in version 3, the host is now capable to answer
queries specific to the group and the source.
IGMP v3 is backwards compatible with other versions of IGMP.
The IGMPv3 Type supported codes are shown below:
Type
0x11
0x12
0x16
0x17
0x22
Timers
As previously mentioned, IGMPv3 incorporates filters to include or exclude sources. These filters are kept updated
using timers. IGMPv3 utilizes two types of timers, one for the group and one for the source. The purpose of the
filter mode is to reduce the reception state of a multicast group so that all members of the multicast group are
satisfied. This filter mode is dependant on membership reports and timers of the multicast group. These filters are
used to maintain a list of multicast sources and groups of multicast receivers that more accurately reflect the actual
sources and receiving groups at any one time on the network.
Source timers are used to keep sources present and active within a multicast group on the Switch. These source
Figure 6-89 IGMP State Transitions
Meaning
Membership Query
Version 1 Membership Report
Version 2 Membership Report
Version 2 Leave Group
IGMPv3 Membership Report
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