What is slowhz?

[Garrett Cooper]

    I see this comment, and I've found references to a
net.inet.tcp.slowhz in Free, Net, and OpenBSDs, but this value can't
be queried anymore.

# grep -r slowhz /sys/
/sys/netinet/ip.h:#define	IPFRAGTTL	60		/* time to live for frags, slowhz */

    Could someone please confirm that slowhz is indeed a half second
value [1], or was it tunable / does it matter anymore?
    For additional context, I'm trying to map IP-MIB::ipReasmTimeout
to a value used in the FreeBSD networking stack, and it looks like
that value is the best candidate.
Thanks!
-Garrett

1. http://markmail.org/message/3xvte6uxrhyb4spn