What are “lost” fragments?
Whenever the fragment or packet is received out of order and you find that out of order fragments or packets are received on all of the links, the lost fragments counter is incremented. Another case is when the out of order fragments are being stored in the list and it reaches a limit (decided based on the SRAM on VIP and whatever is assigned for the bundle), the lost fragments counter is incremented and the next sequence number in the list is taken for processing.