8. List of Timers, Counters, and their Default Values
Most of these timers and counters are configurable. If non-default settings are used, they MUST be consistent among all routers on a single link. Note that the parentheses indicate the value of the corresponding field in the Query message.
8.1. Robustness Variable
The Robustness Variable allows tuning for the expected packet loss on a network. If a network is expected to be lossy, the Robustness Variable may be increased. IGMP is robust to [Robustness Variable] - 1 packet losses.
Default: 2
8.2. Query Interval
The Query Interval is the interval between General Queries sent by the Querier.
Default: 125 seconds
8.3. Query Response Interval
The Max Resp Time inserted into the periodic General Queries.
Default: 100 (10 seconds)
8.4. Group Membership Interval
The Group Membership Interval is the amount of time that must pass before a multicast router decides there are no more members of a group or a particular source on a network.
Value: ([Robustness Variable] * [Query Interval]) + [Query Response Interval]
8.5. Other Querier Present Interval
The Other Querier Present Interval is the length of time that must pass before a multicast router decides that there is no longer another multicast router which should be the Querier.
Value: ([Robustness Variable] * [Query Interval]) + ([Query Response Interval] / 2)
8.6. Startup Query Interval
The Startup Query Interval is the interval between General Queries sent by a Querier on startup.
Default: 1/4 the [Query Interval]
8.7. Startup Query Count
The Startup Query Count is the number of Queries sent out on startup, separated by the [Startup Query Interval].
Default: [Robustness Variable]
8.8. Last Member Query Interval
The Last Member Query Interval is the Max Resp Time inserted into Group-Specific Queries sent in response to Leave Group messages.
Default: 10 (1 second)
8.9. Last Member Query Count
The Last Member Query Count is the number of Group-Specific Queries sent before the router assumes there are no local members.
Default: [Robustness Variable]
8.10. Unsolicited Report Interval
The Unsolicited Report Interval is the time between repetitions of a host's initial report of membership in a group.
Default: 10 seconds
8.11. Older Version Querier Present Timeout
The Older Version Querier Present Timeout is the time-out for transitioning a host back to IGMPv3 mode once an older version query is heard.
Value: ([Robustness Variable] * [Query Interval]) + [Query Response Interval]