Aspects of a system for optimizing fragment size for aggregation at the physical layer may include one more switch ICs and/or physical (PHY) layer ICs that enable reception of data packets via a medium access control layer protocol entity. Each received data packet may be fragmented into a plurality of fragment payloads, wherein a length of each of the plurality of fragment payloads is selected from a plurality of candidate lengths. Each of the plurality of fragment payloads may be sent via a PHY layer protocol entity instance selected from a plurality of PHY layer protocol entity instances.