At the present time, parts of the IN-ADDR.ARPA zone are delegated only on network boundaries which happen to fall on octet boundaries. To aid in the use of blocks of class-C networks, it is recommended that this policy be relaxed and allow the delegation of arbitrary, octet-oriented pieces of the IN-ADDR.ARPA zone.
As an example of this policy change, consider a hypothetical large network provider named "BigNet" which has been allocated the 1024 class-C networks 199.0.0 through 199.3.255. Under current policies, the root domain servers would need to have 1024 entries of the form:
0.0.199.IN-ADDR.ARPA. IN NS NS1.BIG.NET. 1.0.199.IN-ADDR.ARPA. IN NS NS1.BIG.NET. .... 255.3.199.IN-ADDR.ARPA. IN NS NS1.BIG.NET.
By revising the policy as described above, this is reduced only four delegation records:
0.199.IN-ADDR.ARPA. IN NS NS1.BIG.NET. 1.199.IN-ADDR.ARPA. IN NS NS1.BIG.NET. 2.199.IN-ADDR.ARPA. IN NS NS1.BIG.NET. 3.199.IN-ADDR.ARPA. IN NS NS1.BIG.NET.
The provider would then maintain further delegations of naming authority for each individual class-C network which it assigns, rather than having each registered separately. Note that due to the way the DNS is designed, it is still possible for the root nameservers to maintain the delegation information for individual networks for which the provider is unwilling or unable to do so. This should greatly reduce the load on the domain servers for the "top" levels of the IN-ADDR.ARPA domain. The example above illustrates only the records for a single nameserver. In the normal case, there are usually several nameservers for each domain, thus the size of the examples will double or triple in the common cases.