RFC 1518 (rfc1518) - Page 2 of 27
An Architecture for IP Address Allocation with CIDR
Alternative Format: Original Text Document
RFC 1518 CIDR Address Allocation Architecture September 1993
There are two aspects of interest when discussing IP address
allocation within the Internet. The first is the set of
administrative requirements for obtaining and allocating IP
addresses; the second is the technical aspect of such assignments,
having largely to do with routing, both within a routing domain
(intra-domain routing) and between routing domains (inter-domain
routing). This paper focuses on the technical issues.
In the current Internet many routing domains (such as corporate and
campus networks) attach to transit networks (such as regionals) in
only one or a small number of carefully controlled access points.
The former act as subscribers, while the latter act as providers.
The architecture and recommendations provided in this paper are
intended for immediate deployment. This paper specifically does not
address long-term research issues, such as complex policy-based
routing requirements.
Addressing solutions which require substantial changes or constraints
on the current topology are not considered.
The architecture and recommendations in this paper are oriented
primarily toward the large-scale division of IP address allocation in
the Internet. Topics covered include:
- Benefits of encoding some topological information in IP
addresses to significantly reduce routing protocol overhead;
- The anticipated need for additional levels of hierarchy in
Internet addressing to support network growth;
- The recommended mapping between Internet topological entities
(i.e., service providers, and service subscribers) and IP
addressing and routing components;
- The recommended division of IP address assignment among service
providers (e.g., backbones, regionals), and service subscribers
(e.g., sites);
- Allocation of the IP addresses by the Internet Registry;
- Choice of the high-order portion of the IP addresses in leaf
routing domains that are connected to more than one service
provider (e.g., backbone or a regional network).
It is noted that there are other aspects of IP address allocation,
both technical and administrative, that are not covered in this
paper. Topics not covered or mentioned only superficially include:
Rekhter & Li