The value of the object sapIgmpSnpgGrpV1HostExpTime indicates
the time remaining until the system will assume that
there are no longer any IGMPv1 members on this SAP.
Upon hearing any IGMPv1 Membership Report, this value is reset to the
group membership interval. While this time remaining is non-zero, the
system ignores any IGMPv2 and IGMPv3 'leave' messages for this
group that it receives on this SAP.