[Unbound-users] README says "By default 16 ports are used"

[Matthew Dempsky]

Can someone clarify for me what this line in the README[1] means?

  * You can use libevent if you want. libevent is useful when using
     many (10000) outgoing ports. By default 16 ports are used and the
     builtin alternative is equally capable and a little faster.

In particular, what does it mean by "16 ports are used"?

According to [2], Unbound uses per-query source-port randomization.
Is this entry outdated, or does it limit the number of concurrent
queries to 16 or something?

Thanks.

[1] http://unbound.nlnetlabs.nl/svn/trunk/README
[2] http://www.unbound.net/documentation/patch_announce102.html