Number of datagrams retransmitted by this source.

This count is incremented under the same circumstances as retransmissionBytesSent, below. In a normal, light-loss scenario, most NAKs received induce a retransmission. When losses become heavy and/or many receiver transports begin losing the same datagrams, NCF-related no-retransmit counts (naksIgnored, naksShed and naksIgnoredRetransmitDelay) may begin to inflate, and retransmissions retransmissionsSent) may become significantly lower than NAKS received (naksReceived). 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.