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+Network Working Group E. Gerich
+Request for Comments: 1366 Merit
+ October 1992
+
+
+ Guidelines for Management of IP Address Space
+
+Status of this Memo
+
+ This memo provides information for the Internet community. It does
+ not specify an Internet standard. Distribution of this memo is
+ unlimited.
+
+Abstract
+
+ This document has been reviewed by the Federal Engineering Task Force
+ (FEPG) on behalf of the Federal Networking Council (FNC), the co-
+ chairs of the International Engineering Planning Group (IEPG), and
+ the Reseaux IP Europeens (RIPE). There was general consensus by
+ those groups to support the recommendations proposed in this document
+ for management of the IP address space.
+
+1.0 Introduction
+
+ With the growth of the Internet and its increasing globalization,
+ much thought has been given to the evolution of the network number
+ allocation and assignment process. RFC 1174, "Identifier Assignment
+ and Connected Status", dated August 1990 recommends that the Internet
+ Registry (IR) continue as the principal registry for network numbers;
+ however, the IR may allocate blocks of network numbers and the
+ assignment of those numbers to qualified organizations. The IR will
+ serve as the default registry in cases where no delegated
+ registration authority has been identified.
+
+ The distribution of the registration function is desirable, and in
+ keeping with that goal, it is necessary to develop a plan which
+ manages the distribution of the network number space. The demand for
+ network numbers has grown significantly within the last two years and
+ as a result the allocation of network numbers must be approached in a
+ more systematic fashion.
+
+ This document proposes a plan which will forward the implementation
+ of RFC 1174 and which defines the allocation and assignment of the
+ network number space. There are three major topics to be addressed:
+
+ 1) Qualifications for Distributed Regional Registries
+
+ 2) Allocation of the Network Number Space by the Internet Registry
+
+
+
+Gerich [Page 1]
+
+RFC 1366 Guidelines for Management of IP Address Space October 1992
+
+
+ 3) Assignment of the Network Numbers
+
+2.0 Qualifications for Distributed Regional Registries
+
+ The major reason to distribute the registration function is that the
+ Internet serves a more diverse global population than it did at its
+ inception. This means that registries which are located in distinct
+ geographic areas may be better able to serve the local community in
+ terms of language and local customs. While there appears to be wide
+ support for the concept of distribution of the registration function,
+ it is important to define how the candidate delegated registries will
+ be chosen and from which geographic areas.
+
+ Based on the growth and the maturity of the Internet in Europe,
+ Central/South America and the Pacific Rim areas, it is desirable to
+ consider delegating the registration function to an organization in
+ each of those geographic areas. Until an organization is identified
+ in those regions, the IR will continue to serve as the default
+ registry. The IR remains the root registry and continues to provide
+ the registration function to all those regions not covered by
+ distributed regional registries. And as other regions of the world
+ become more and more active in the Internet, the IANA and the IR may
+ choose to look for candidate registries to serve the populations in
+ those geographic regions.
+
+ It is important that the regional registry is unbiased and and widely
+ recognized by network providers and subscribers within the geographic
+ region. It is also important that there is just a single regional
+ registry per geographical region at this level to provide for
+ efficient and fair sub-allocation of the address space. To be
+ selected as a distributed regional registry an organization should
+ meet the following criteria:
+
+ a) networking authorities within the geographic area
+ legitimize the organization
+
+ b) the organization is well-established and has
+ legitimacy outside of the registry function
+
+ c) the organization will commit appropriate resources to
+ provide stable, timely, and reliable service
+ to the geographic region
+
+ d) the commitment to allocate IP numbers according to
+ the guidelines established by the IANA and the IR
+
+ e) the commitment to coordinate with the IR to establish
+ qualifications and strategies for sub-allocations of
+
+
+
+Gerich [Page 2]
+
+RFC 1366 Guidelines for Management of IP Address Space October 1992
+
+
+ the regional allocation.
+
+ The distributed regional registry is empowered by the IANA and the IR
+ to provide the network number registration function to a geographic
+ area. It is possible for network subscribers to contact the IR
+ directly. Depending on the circumstances the network subscriber may
+ be referred to the regional registry, but the IR will be prepared to
+ service any network subscriber if necessary.
+
+3.0 Allocation of the Network Number Space by the Internet Registry
+
+ The Class A portion of the number space represents 50% of the total
+ IP numbers; Class B is 25% of the total; Class C is approximately 12%
+ of the total. Table 1 shows the current allocation of the IP network
+ numbers.
+
+ Total Allocated Allocated (%)
+ Class A 126 49 38%
+ Class B 16383 7354 45%
+ Class C 2097151 44014 2%
+
+ Table 1: Network Number Statistics (June 1992) [1]
+
+ Class A and B network numbers are a limited resource and therefore
+ the entire number space will be retained by the IR. No allocations
+ from the Class A and B network numbers will be made to distributed
+ regional registries at this time.
+
+ The Class C network number space will be divided into allocatable
+ blocks which will be reserved by the IANA and IR for allocation to
+ distributed regional registries. In the absence of designated
+ regional registries in geographic areas, the IR will assign addresses
+ to networks within those geographic areas according to the Class C
+ allocation divisions.
+
+ A preliminary inspection of the Class C IP network numbers shows that
+ the number space with prefixes 192 and 193 are assigned. The
+ remaining space from prefix 194 through 223 is mostly unassigned.
+
+ The IANA and the IR will reserve the upper half of this space which
+ corresponds to the IP address range of 208.0.0.0 through
+ 223.255.255.255. Network numbers from this portion of the Class C
+ space will remain unallocated and unassigned until further notice.
+
+ The remaining Class C network number space will be allocated in a
+ fashion which is compatible with potential address aggregation
+ techniques. It is intended to divide this address range into eight
+ equally sized address blocks.
+
+
+
+Gerich [Page 3]
+
+RFC 1366 Guidelines for Management of IP Address Space October 1992
+
+
+ 192.0.0.0 - 193.255.255.255
+ 194.0.0.0 - 195.255.255.255
+ 196.0.0.0 - 197.255.255.255
+ 198.0.0.0 - 199.255.255.255
+ 200.0.0.0 - 201.255.255.255
+ 202.0.0.0 - 203.255.255.255
+ 204.0.0.0 - 205.255.255.255
+ 206.0.0.0 - 207.255.255.255
+
+ Each block represents 131,072 addresses or approximately 6% of the
+ total Class C address space.
+
+ It is proposed that a broad geographic allocation be used for these
+ blocks. At present there are four major areas of address allocation:
+ Europe, North America, Pacific Rim, and South & Central America.
+
+ In particular, the top level block allocation be designated as
+ follows:
+
+ Multi-regional 192.0.0.0 - 193.255.255.255
+ Europe 194.0.0.0 - 195.255.255.255
+ Others 196.0.0.0 - 197.255.255.255
+ North America 198.0.0.0 - 199.255.255.255
+ Central/South
+ America 200.0.0.0 - 201.255.255.255
+ Pacific Rim 202.0.0.0 - 203.255.255.255
+ Others 204.0.0.0 - 205.255.255.255
+ Others 206.0.0.0 - 207.255.255.255
+
+ It is proposed that the IR, and any designated regional registries,
+ allocate addresses in conformance with this overall scheme. Where
+ there are qualifying regional registries established, primary
+ responsibility for allocation from within that block will be
+ delegated to that registry.
+
+ The ranges designated as "Others" permit flexibility in network
+ number assignments which are outside of the geographical regions
+ already allocated. The range listed as multi-regional represents
+ network numbers which have been assigned prior to the implementation
+ of this plan. It is proposed that the IANA and the IR will adopt
+ these divisions of the Class C network number space and will begin
+ assigning network numbers accordingly.
+
+4.0 Assignment of the Network Number Space
+
+ The exhaustion of the IP address space is a topic of concern for the
+ entire Internet community. This plan for the assignment of Class A,
+ B, or C IP numbers to network subscribers has two major goals:
+
+
+
+Gerich [Page 4]
+
+RFC 1366 Guidelines for Management of IP Address Space October 1992
+
+
+ 1) to reserve a portion of the IP number space so that it may be
+ available to transition to a new numbering plan
+
+ 2) to assign the Class C network number space in a fashion which
+ is compatible with proposed address aggregation techniques
+
+4.1 Class A
+
+ The Class A number space can support the largest number of unique
+ host identifier addresses and is also the class of network numbers
+ most sparsely populated. There are only approximately 77 Class A
+ network numbers which are unassigned, and these 77 network numbers
+ represent about 30% of the total network number space.
+
+ The IANA will retain sole responsibility for the assignment of Class
+ A network numbers. The upper half of the Class A number space will be
+ reserved indefinitely (IP network addresses 64.0.0.0 through
+ 127.0.0.0). While it is expected that no new assignments of Class A
+ numbers will take place in the near future, any organization
+ petitioning the IANA for a Class A network number will be expected to
+ provide a detailed technical justification documenting network size
+ and structure. Class A assignments are at the IANA's discretion.
+
+4.2 Class B
+
+ Previously organizations were recommended to use a subnetted Class B
+ network number rather than multiple Class C network numbers. Due to
+ the scarcity of Class B network numbers and the under utilization of
+ the Class B number space by most organizations, the recommendation is
+ now to use multiple Class Cs where practical.
+
+ The IANA and the IR will maintain sole responsibility for the Class B
+ number space. Where there are designated regional registries, those
+ registries will act in an auxiliary capacity in evaluating requests
+ for Class B numbers. Organizations applying for a Class B network
+ number should fulfill the following criteria:
+
+ 1) the organization presents a subnetting plan which
+ documents more than 32 subnets within its organizational
+ network
+
+ AND
+
+ 2) the organization has more than 4096 hosts.
+
+ These criteria assume that an organization which meets this profile
+ will continue to grow and that assigning a Class B network number to
+ them will permit network growth and reasonable utilization of the
+
+
+
+Gerich [Page 5]
+
+RFC 1366 Guidelines for Management of IP Address Space October 1992
+
+
+ assigned number space. There may be circumstances where it will be
+ impossible to utilize a block of Class C network numbers in place of
+ a Class B. These situations will be considered on a case-by-case
+ basis.
+
+4.3 Class C
+
+ Section 3 of this document recommends a division of the Class C
+ number space. That division is primarily an administrative division
+ which lays the groundwork for distributed network number registries.
+ This section deals with how network numbers are assigned from within
+ those blocks. Sub-allocations of the block to sub-registries is
+ beyond the scope of this paper.
+
+ By default, if an organization requires more than a single Class C,
+ it will be assigned a bit-wise contiguous block from the Class C
+ space allocated for its geographic region.
+
+ For instance, an European organization which requires fewer than 2048
+ unique IP addresses and more than 1024 would be assigned 8 contiguous
+ class C network numbers from the number space reserved for European
+ networks, 194.0.0.0 - 195.255.255.255. If an organization from
+ Central America required fewer than 512 unique IP addresses and more
+ than 256, it would receive 2 contiguous class C network numbers from
+ the number space reserved for Central/South American networks,
+ 200.0.0.0 - 201.255.255.255.
+
+ The IR or the registry to whom the IR has delegated the registration
+ function will determine the number of Class C network numbers to
+ assign to a network subscriber based on the following criteria:
+
+ Organization Assignment
+
+ 1) requires fewer than 256 addresses 1 class C network
+ 2) requires fewer than 512 addresses 2 contiguous class C networks
+ 3) requires fewer than 1024 addresses 4 contiguous class C networks
+ 4) requires fewer than 2048 addresses 8 contiguous class C networks
+ 5) requires fewer than 4096 addresses 16 contiguous class C networks
+
+ The number of addresses that a network subscriber indicates that it
+ needs should be based on a 24 month projection.
+
+ The maximal block of class C nets that should be assigned to a
+ subscriber consists of sixteen contiguous class C networks which
+ corresponds to a single IP prefix the length of which is twelve bits.
+ If a subscriber has a requirement for more than 4096 unique IP
+ addresses it should most likely receive a Class B net number.
+
+
+
+
+Gerich [Page 6]
+
+RFC 1366 Guidelines for Management of IP Address Space October 1992
+
+
+5.0 Conclusion
+
+ This proliferation of class C network numbers may aid in preserving
+ the scarcity of class A and B numbers, but it is sure to accelerate
+ the explosion of routing information carried by Internet routers.
+ Inherent in these recommendations is the assumption that there will
+ be modifications in the technology to support the larger number of
+ network address assignments due to the decrease in assignments of
+ Class A and B numbers and the proliferation of Class C assignments.
+
+ Many proposals have been made to address the rapid growth of network
+ assignments and a discussion of those proposals is beyond the scope
+ and intent of this paper.
+
+ These recommendations for management of the current IP network number
+ space only profess to delay depletion of the IP address space, not to
+ postpone it indefinitely.
+
+6.0 Acknowledgements
+
+ The author would like to acknowledge the substantial contributions
+ made by the members of the following two groups, the Federal
+ Engineering Planning Group (FEPG) and the International Engineering
+ Planning Group (IEPG). This document also reflects many concepts
+ expressed at the IETF Addressing BOF which took place in Cambridge,
+ MA in July 1992. In addition, Jon Postel (ISI) and Yakov Rekhter
+ (T.J. Watson Research Center, IBM Corp.) reviewed this document and
+ contributed to its content. The author thanks those groups and
+ individuals who have been sighted for their comments.
+
+7.0 References
+
+ [1] Wang, Z., and J. Crowcroft, "A Two-Tier Address Structure for the
+ Internet: A Solution to the Problem of Address Space Exhaustion",
+ RFC 1335, University College London, May 1992.
+
+ [2] "Internet Domain Survey", Network Information Systems Center, SRI
+ International, July 1992.
+
+ [3] Ford, P., "Working Draft - dated 6 May 1992", Work in Progress.
+
+ [4] Solensky F., and F. Kastenholz, "A Revision to IP Address
+ Classifications", Work in Progress, March 1992.
+
+ [5] Fuller, V., Li, T., Yu, J., and K. Varadha, "Supernetting: an
+ Address Assignments and Aggregation Strategy", RFC 1338, BARRNet,
+ cisco, Merit, OARnet, June 1992.
+
+
+
+
+Gerich [Page 7]
+
+RFC 1366 Guidelines for Management of IP Address Space October 1992
+
+
+ [6] Rekhter, Y., and T. Li, "Guidelines for IP Address Allocation",
+ Work in Progress, August 1992.
+
+ [7] Cerf, V., "IAB Recommended Policy on Distributing Internet
+ Identifier Assignment and IAB Recommended Policy Change to
+ Internet 'Connected' Status", RFC 1174, CNRI, August 1990.
+
+Security Considerations
+
+ Security issues are not discussed in this memo.
+
+Author's Address
+
+ Elise Gerich
+ Merit Computer Network
+ 1075 Beal Avenue
+ Ann Arbor, MI 48109-2112
+
+ Phone: (313) 936-3000
+ EMail: epg@MERIT.EDU
+
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+Gerich [Page 8]
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