D-Link DGS-3324SR Product Manual - Page 214

Group Membership Interval x Robustness Variable + One Query Response Interval

Page 214 highlights

xStack DGS/DXS-3300 Series Layer 3 Stackable Gigabit Ethernet Switch User Manual 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 part of a report packet. If the filter mode is exclude, traffic is being denied from at least one specific source, yet other hosts may be accepting traffic from the multicast group. If the group timer expires for the multicast group, the filter mode is changed to include and other hosts can receive traffic from the source. If no group report packet is received and the filter mode is include, the Switch presumes that traffic from the source is no longer wanted on the attached network and the source record list is then deleted after all source timers expire. If there is no source list record in the multicast group, the multicast group will be deleted from the Switch. Timers are also used for IGMP version 1 and 2 members, which are a part of a multicast group when the Switch is running IGMPv3. This timer is based on a host within the multicast group that is running IGMPv1 or v2. Receiving a group report from an IGMPv1 or v2 host within the multicast group will refresh the timer and keep the v1 and/or v2 membership alive in v3. NOTE: The length of time for all timers utilized in IGMPv3 can be determined using IGMP configurations to perform the following calculation: (Group Membership Interval x Robustness Variable) + One Query Response Interval 199

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xStack DGS/DXS-3300 Series Layer 3 Stackable Gigabit Ethernet Switch User Manual
199
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 part of a report packet. If the filter mode is exclude, traffic is being denied from at least one specific source, yet
other hosts may be accepting traffic from the multicast group. If the group timer expires for the multicast group, the filter
mode is changed to include and other hosts can receive traffic from the source. If no group report packet is received and the
filter mode is include, the Switch presumes that traffic from the source is no longer wanted on the attached network and the
source record list is then deleted after all source timers expire. If there is no source list record in the multicast group, the
multicast group will be deleted from the Switch.
Timers are also used for IGMP version 1 and 2 members, which are a part of a multicast group when the Switch is running
IGMPv3. This timer is based on a host within the multicast group that is running IGMPv1 or v2. Receiving a group report
from an IGMPv1 or v2 host within the multicast group will refresh the timer and keep the v1 and/or v2 membership alive
in v3.
NOTE:
The length of time for all timers utilized in IGMPv3 can be determined using
IGMP configurations to perform the following calculation:
(Group Membership Interval x Robustness Variable) + One Query Response Interval