This read-only integer reports the observed differential delay, in milliseconds, between the various physical links bundled together in an IMA group. Administrators watch this value because IMA requires all member links to have reasonably similar propagation delay for cells to be correctly reassembled in order; excessive differential delay can force the group to fail or drop a link. For example, if imaObsDiffDelay climbs sharply after a carrier reroutes one of the T1 circuits over a longer path, the admin would expect to see related alarms like failedDueToBadDiffDelay on imaPortState.