An ATTACHMENT entry containing information common to a given set of ATTACHMENTs. The ATTACHMENT Resource represents a PORT or a pair of PORTs plus the optional associated optical bypass that are managed as a functional unit. Because of its relationship to the PORT Objects, there is a natural association of ATTACHMENT Resource Indices to the PORT Indices. The resource index for the ATTACHMENT is equal to the associated PORT index for 'single-attachment' and 'concentrator' type snmpFddiATTACHMENTClasses. For 'dual-attachment' Classes, the ATTACHMENT Index is the PORT Index of the A PORT of the A/B PORT Pair that represents the ATTACHMENT.