(LSR) A device that typically reSideSSomewhere in the middle of a network and iS capable of forwarding datagramS baSed upon a label. In many caSeS, eSpecially early verSionS of MPLS networkS, a LSR will typically be a modified ATMSwitch that forwardS datagramS baSed upon a label in the VPI/VCI field. (1999-06-14)