Your message was unreadable, you should use text form for messages sent
to the ITS.
In any case, according to many sources, the default values for TCP
buffers can be pretty small. Usually, they can be configured
system-wide at the OS level (see tcp(7)), or even auto-tuned.
Personally, I have no objections in optionally allowing to hard-set the
buffer sizes to values one considers appropriate for the intended use of
slapd. Since the optimal size roughly depends on latency and bandwidth,
this may probably need to be configured on a per-listener basis, actually.
However, in deployments where this problem becomes critical, usually
hardware dedicated to slapd is used, so system-wide tuning (and
auto-tuning) would be the preferred option anyway. Manual setting
should be used only when system-wide or auto-tuning is not available or
accessible for some reason.