What are "forward retransmits"?

[Itai Fiat Gecht]

Hi,

What are the "forward retransmits" shown by netstat? Is there an RFC
or other documentation describing them? I could not figure this out
from tcp_output.c.

Sample netstat output:

    106926 fast retransmits
    5149 forward retransmits
    915 retransmits in slow start

Sincerely yours,

Itai