lame delegation to Route 53

#
# 委任元の x.nic.xyz. に聞いた時
#
$ dig +norec +noall +auth NS sub.tcpreplay.xyz. @x.nic.xyz.
tcpreplay.xyz.		3600	IN	NS	ns-383.awsdns-47.com.   # com(o)
tcpreplay.xyz.		3600	IN	NS	ns-656.awsdns-18.net.   # net(o)
tcpreplay.xyz.		3600	IN	NS	ns-1117.awsdns-11.org.  # org(o)
tcpreplay.xyz.		3600	IN	NS	ns-1601.awsdns-08.co.uk.# co.uk(o)

#
# 委任先の 4つの NS に聞いた時
#
$ dig +norec +noall +ans +auth NS sub.tcpreplay.xyz. @ns-383.awsdns-47.com.
sub.tcpreplay.xyz.	172800	IN	NS	ns-383.awsdns-47.com.   # com(o) <===
sub.tcpreplay.xyz.	172800	IN	NS	ns-625.awsdns-14.net.   # net(x)
sub.tcpreplay.xyz.	172800	IN	NS	ns-1236.awsdns-26.org.  # org(x)
sub.tcpreplay.xyz.	172800	IN	NS	ns-1689.awsdns-19.co.uk.# co.uk(x)

$ dig +norec +noall +ans +auth NS sub.tcpreplay.xyz. @ns-656.awsdns-18.net.
sub.tcpreplay.xyz.	172800	IN	NS	ns-347.awsdns-43.com.   # com(x)
sub.tcpreplay.xyz.	172800	IN	NS	ns-656.awsdns-18.net.   # net(o) <===
sub.tcpreplay.xyz.	172800	IN	NS	ns-1192.awsdns-21.org.  # org(x)
sub.tcpreplay.xyz.	172800	IN	NS	ns-1640.awsdns-13.co.uk.# co.uk(x)

$ dig +norec +noall +ans +auth NS sub.tcpreplay.xyz. @ns-1117.awsdns-11.org.
sub.tcpreplay.xyz.	172800	IN	NS	ns-82.awsdns-10.com.    # com(x)
sub.tcpreplay.xyz.	172800	IN	NS	ns-970.awsdns-57.net.   # net(x)
sub.tcpreplay.xyz.	172800	IN	NS	ns-1117.awsdns-11.org.  # org(o) <===
sub.tcpreplay.xyz.	172800	IN	NS	ns-1614.awsdns-09.co.uk.# co.uk(x)

$ dig +norec +noall +ans +auth NS sub.tcpreplay.xyz. @ns-1601.awsdns-08.co.uk.
sub.tcpreplay.xyz.	172800	IN	NS	ns-214.awsdns-26.com.   # com(x)
sub.tcpreplay.xyz.	172800	IN	NS	ns-781.awsdns-33.net.   # net(x)
sub.tcpreplay.xyz.	172800	IN	NS	ns-1161.awsdns-17.org.  # org(x)
sub.tcpreplay.xyz.	172800	IN	NS	ns-1601.awsdns-08.co.uk.# co.uk(o) <===