. Number of individual NAKs sent by the receiver transport.

This may differ from the tally of lost datagrams (below) due to reasons such as

• Other receiver transports may have already sent a NAK for the same lost datagram, resulting in a retransmitted lost datagram (or an NCF) to arrive at this receiver transport before it has a chance to issue a NAK, or
• During periods of heavy loss, receiver transports may be forced to issue multiple NAKs per lost datagram (controlled by the transport's configuration options for NAK generation interval and NAK backoff interval) until either the retransmission is received or the datagram is declared unrecovered (which may ultimately lead to UM delivering an LBM_MSG_UNRECOVERABLE_LOSS notification to the receiver application).

This method returns a value from the first set of statistics encapsulated within this object and would normally be used when the object has been created using a specific source to instantiate the class.