This read-write value selects the cell-alignment mechanism used by the DS3 framer: hec(1), the default, using HEC-based alignment with standard 53-octet cells, or plcp(2), using PLCP framing overhead which produces 57-octet cells. An admin sets it to match the cell-delineation method expected at the far end of a DS3 ATM link, since a mismatch would prevent correct cell alignment and break the ATM connection. For example, an admin connecting to carrier equipment that requires PLCP framing would change this setting from the default hec(1) to plcp(2).