Igmp Version 3 - D-Link DES-6500 - Switch User Manual

IGMP version 2 introduces some enhancements such as a method to elect a multicast querier for each LAN, an explicit leave
message, and query messages that are specific to a given group.
The states a computer will go through to join or to leave a multicast group are shown below:

IGMP Version 3

The current release of the xStack DES-6500 switch series 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 timers are
refreshed if a group report packet is received by the Switch, which holds information pertaining to the active source group record
xStack DES-6500 Modular Layer 3 Chassis Ethernet Switch User Manual
Figure 6- 144. 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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