This value indicates which fabric side this internal link record belongs to, matching the identity of the Fabric Interconnect it's tracked on. It matters on the same internal chassis backplane link, but the record kept on the Fabric Interconnect (switch) side rather than the IOM/server side because a switch-side record only ever exists on the fabric interconnect that terminates the physical link, so this field simply confirms which A/B side this particular record describes. A locale of fabric-A on this link's fabric-interconnect side confirms this record describes the connection as seen specifically by fabric interconnect A.