Hi Neeraj Mishra,
In PDCP time based discard is used to prevent the buffer overflow in the transmitter. Each SDU can stay in the transmission buffer only for the configured time period in the PDCP entity. This configured time depends on the delay requirement of radio bearer.
Thus time based discard is used to ensure that the requirement of the maximum transmission delay of PDCP SDU is met. once the SDU from the upper layer is received in PDCP the transmitter starts the discard timer for the SDU. Once the discard timer expires the PDCP transmitter discard the PDCP SDU and indicate the RLC to discard the corresponding PDCP PDU if the PDU has already been delivered to RLC. Then the RLC layer will discard the PDCP PDU if no segment is transmitted to the receiver.
