i have just used the input file feature with a comment and for convenience i listed two fedora iso files from the same domain. the result was one (the second link) was downloading at over 7MB/s and the other was below 300kB/s. once one file was done, the other download did not ramp up to 7MB/s, and it stayed at under 300kB/s.

is it possible that with a input file like

example.com/file1
example.com/file2
example.com/file3
example-bis.com/file4

dlm starts the first and fourth file downloads in parallel, but for links 1, 2, and 3, it downloads them in sequence (maybe even reusing the connection without a new handshake)?