All ISPs receiving /16 prefix blocks from the InterNIC will be responsible
for maintaining all IN-ADDR.ARPA domain records for their respective
customers. The InterNIC Registry will only be responsible for the
maintenance of IN-ADDR.ARPA domain records for those CIDR blocks with
prefixes longer than /16 issued directly from the InterNIC.
I think you mean shorter, as in:
The InterNIC Registry will only be responsible for the
maintenance of IN-ADDR.ARPA domain records for those CIDR blocks with
prefixes SHORTER than /16 issued directly from the InterNIC.
No, I think he means longer. IN-ADDR.ARPA can only be delegated on octet
boundaries, so IN-ADDR for /16 and shorter prefixes will be delegated in /16
chunks. IN-ADDR for prefixes longer than /16 must still be maintained by the
root, since they cannot be delegated.
For example, assume an ISP has been allocated the prefix 204.160/14. Along with
this, the InterNIC will delegate the corresponding IN-ADDR domains:
160.204.IN-ADDR.ARPA
161.204.IN-ADDR.ARPA
162.204.IN-ADDR.ARPA
163.204.IN-ADDR.ARPA
If the ISP were instead only assigned 204.160.0/17, the associated IN-ADDR
range would be:
0.160.204.IN-ADDR.ARPA
...
127.160.204.IN-ADDR.ARPA
which is not octet-aligned and therefore cannot be delegated.
--Vince