VIAVI TestCenter: Why is IGMPv3 client sending IGMPv2 Reports?

VIAVI TestCenter: Why is IGMPv3 client is sending IGMPv2 Reports?

• RFC 3376 • If an IGMPv3 host receives an IGMPv2 query it must respond with an IGMPv2 Report.  Once the network stops sending IGMPv2 queries, the host will revert back to IGMPv3 after its compatibility mode times out. The timeout value is ((the Robustness Variable) times (the Query Interval in the last Query received)) plus (one Query Response Interval). • Of course this is only if the network stops sending IGMPv2 queries. • During this time it will not send an IGMPv3 report even if it receives IGMPv3 query. • On VIAVI TestCenter, when the compatibility mode is engaged, stop/start device will not clear the issue. • You can clear this issue by inactivating IGMP on that device, click apply, then activate IGMP on that device, and click apply again. • Or you can wait for the timeout mention earlier. • RFC 4604 - Updated RFC-3376 to support Source Specific Multicast (SSM) • The use of source-specific multicast is facilitated by small changes to the SFGMP protocols on both hosts and routers. • 2.2.1.  IGMPv1/v2 and MLDv1 Reports  • RFC-3376 and RFC-3810 specify that a host MAY allow an older-version report to suppress its own IGMPv3 or MLDv2 Membership Record. • An SSM-aware host, however, MUST NOT allow its report to be suppressed in this situation.  Suppressing reports in this scenario would provide an avenue for an attacker to deny SSM service to other hosts on the link. • It is not clear as to how an IGMPv3 host should be implemented in a network with both IGMPv2 and IGMPv3 queries but as indicated in RFC-4604, the IGMPv3 SSM report should not be suppressed. • Although the next section in 2.2.3, it mentions all routers on the IGMPv3 SSM network should be compliant to this spec. In this case it doesn't seem there should be any IGMPv2 queries. This makes things a bit unclear. • RFC 5790 -  Light Weight IGMPv3/MLDv2 support that includes SSM support. • RFC-5790 section 6.2.1 mentions "the choice to enable or disable the use of backward compatibility may be configurable". • It seems this specification deals with the SSM problem by completely disabling IGMPv2 compatibility.