Document denial of service vector via oversized AXFR, IXFR, or Dynamic DNS
updates in BIND, Knot, NSD, and PowerDNS

Security: CVE-2016-6170
Security: CVE-2016-6171
Security: CVE-2016-6172
Security: CVE-2016-6173
Security: https://vuxml.FreeBSD.org/freebsd/7d08e608-5e95-11e6-b334-002590263bf5.html