But, "man 5 ldap.conf " does not seem to list those defaults. Instead it says this about them:

       NETWORK_TIMEOUT <integer>
              Specifies  the timeout (in seconds) after which
              the poll(2)/select(2)  following  a  connect(2)
              returns in case of no activity.

       TIMEOUT <integer>
              Specifies a timeout (in  seconds)  after  which
              calls to synchronous LDAP APIs will abort if no
              response  is  received.   Also  used  for   any
              ldap_result(3)  calls  where a NULL timeout pa‐
              rameter is supplied.

So, I wonder what is being used as default for these.

In case there is none, that would come down to 'infinite'. But I don't find that information either.

Something similar goes for 'keepalive', that is described as:

"The keepalive parameter sets the values of idle, probes, and interval used to check whether a socket is alive; idle is the number of seconds a connection needs to remain idle before TCP starts sending keepalive probes; probes is the maximum number of keepalive probes TCP should send before dropping the connection; interval is interval in seconds between individual keepalive probes. Only some systems support the customization of these values; the keepalive parameter is ignored otherwise, and system-wide settings are used. For example, keepalive="240:10:30" will send a keepalive probe 10 times, every 30 seconds, after 240 seconds of idle activity. If no response to the probes is received, the connection will be dropped."

The "man 5 ldap.conf" has these keepalive params:

       KEEPALIVE_IDLE
              Sets/gets the number of  seconds  a  connection
              needs  to remain idle before TCP starts sending
              keepalive probes. Linux only.

       KEEPALIVE_PROBES
              Sets/gets  the  maximum  number  of   keepalive
              probes TCP should send before dropping the con‐
              nection. Linux only.

       KEEPALIVE_INTERVAL
              Sets/gets the interval in seconds between indi‐
              vidual keepalive probes.  Linux only.

Again, no defaults.

We do run this on Linux, and the kernel has corresponding values for:

root@foo:/proc/sys/net/ipv4# for i in tcp_keepalive_*; do echo "$i = $(cat $i)"; done
tcp_keepalive_intvl = 75
tcp_keepalive_probes = 9
tcp_keepalive_time = 7200

So, I'm guessing in my case "keepalive" will use "7200:9:75" - right?

I.e. the defaults are from the OS' TCP stack configuration.