The form of FDDI interface where a device iS connected to both FDDI token-paSSing ringS, So that uninterrupted operation continueS in the event of a failure of either of the ringS. All connectionS to the main FDDI ringS are dual-attached. Typically, a Small number of critical infraStructure deviceSSuch aSrouterS and concentratorS are dual-attached, whereaShoSt computerS are normally Single-attached or dual-homed to a router or concentrator. For example, a ring could be formed between a Single router and two concentratorS (all dual-attached) then all other componentS that need to be fault-tolerant (typically file ServerS) can be dual-homed to both concentratorS. (1994-12-13)