RFC 1335 (rfc1335) - Page 2 of 7
A Two-Tier Address Structure for the Internet: A Solution to the Problem of Address Space Exhaustion
Alternative Format: Original Text Document
RFC 1335 Two-Tier Address Structure for the Internet May 1992
immediate problem [1-4]. The Supernetting and C-sharp schemes
attempt to make the Class C numbers more usable by re-defining the
way in which Class C network numbers are classified and assigned
[3,4]. Both schemes require modifications to the exterior routing
algorithms and global coordination across the Internet may be
required for the deployment. The two schemes do not expand the total
number of addresses available to the Internet and therefore can only
be used as a short-term fix for next two or three years. Schemes
have also been put forwarded in which the 32-bit address field is
replaced with a field of the same size but with different meaning and
the gateways on the boundary re-write the address when the packet
crossed the boundary [1,2,5]. Such schemes, however, requires
substantial changes to the gateways and the exterior routing
algorithm.
In this paper, we present an alternative solution to the problem of
address space exhaustion. The "Dual Network Addressing (DNA)" scheme
proposed here is based on a two-tier address structure and sharing of
addresses. It requires no modifications to the exterior routing
algorithms and any networks can adopt the scheme individually at any
time without affecting other networks.
The Scheme
The DNA scheme attempts to reduce the waste in using the Internet
addresses. A useful analogy to our scheme is the extension system
used in the telephone system. Many large organizations usually have
extensive private telephone networks for internal use and at the mean
time hire a limited number of external lines for communications with
the outside world. In such a telephone system, important offices may
have direct external lines and telephones in the public areas may be
restricted to internal calls only. The majority of the telephones
can usually make both internal calls and external calls. But they
must share a limited number of external lines. When an external call
is being made, a pre-defined digit has to be pressed so that an
external line can be allocated from the poll of external lines.
In the DNA scheme, there are two types of Internet addresses:
Internal addresses and External addresses. An internal address is an
Internet address only used within one network and is unique only
within that network. An interface with an internal address can only
communicate with another interface with an internal address in the
same network. An external address is unique in the entire Internet
and an interface with an external address can communicate directly to
another interface with an external address over the Internet. All
current Internet addresses are external addresses.
In effect, the external addresses form one global Internet and the
Wang & Crowcroft