Certain aspects of the present disclosure provide methods and apparatuses for determining a packet number for a packet, based on a transmit packet number (TPN), transmitted with the packet, a locally maintained base packet number (BPN), and a value of the TPN relative to one or more edges of a locally-maintained receive window. An example method generally includes receiving a packet having a transmitted packet number (TPN), maintaining a base packet number (BPN), maintaining a receive window defined by a first edge a and a second edge b, determining a value i of the TPN relative to at least one of the first edge a or the second edge b of the receive window, and calculating a packet number (PN) for the packet based on the TPN, the BPN, and the determination.