RFC 1366

Okay bestie, let's get into RFC 1366 🦋 It's titled Guidelines for Management of IP Address Space, written by E. Gerich at Merit, and dated October 1992. It's Informational, so it's giving "here's some info" rather than "this is a standard" 💅 The title block doesn't list anything it obsoletes or updates, so no drama there 🙈

Status of this Memo 🌸

This memo is giving information for the Internet community 💖 It does not specify an Internet standard, so it's guidance with a purpose, not an official spec ✨ Distribution is unlimited, so share it with everyone 🌈

Abstract 🎀

This doc was 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). Those groups generally agreed on the recommendations for managing the IP address space, which is honestly iconic 👑

1.0 Introduction 🧚

Okay so the Internet has grown and gone global, and people have been thinking a lot about how network numbers get allocated and assigned 🌍 RFC 1174, "Identifier Assignment and Connected Status", dated August 1990, recommends that the Internet Registry (IR) stay the principal registry for network numbers. The IR can allocate blocks of network numbers and assign those numbers to qualified organizations, and it serves as the default registry wherever no delegated registration authority has been identified.

Distributing the registration function is desirable 🙌 so we need a plan that manages how the network number space gets distributed. The demand for network numbers has grown a ton in the last two years, so allocation needs a more systematic approach 📈

This document proposes a plan that will forward the implementation of RFC 1174 and defines the allocation and assignment of the network number space. There are three major topics:

• 1) Qualifications for Distributed Regional Registries
• 2) Allocation of the Network Number Space by the Internet Registry
• 3) Assignment of the Network Numbers

2.0 Qualifications for Distributed Regional Registries 💫

The big reason to distribute registration is that the Internet now serves a way more diverse global population than it did at the start 🌸 Registries in different geographic areas may be better able to serve their local community when it comes to language and local customs. Lots of people support distributing this function, but it's important to define how candidate delegated registries get chosen and which geographic areas they cover 🗺️

Based on how mature the Internet is getting in Europe, Central/South America, and the Pacific Rim, it's desirable to consider delegating the registration function to an organization in each of those areas 🌏 Until an organization is identified in those regions, the IR keeps serving as the default registry. The IR remains the root registry and keeps providing registration to every region not covered by a distributed regional registry. As other regions become more active on the Internet, the IANA and the IR may look for candidate registries to serve those populations 🦋

A regional registry has to be unbiased and widely recognized by network providers and subscribers in its geographic region 🫶 It's also important that there's just one regional registry per geographic region at this level, so that sub-allocation of the address space stays efficient and fair. 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 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. Network subscribers can contact the IR directly 📞 Depending on the circumstances, a 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 is 50% of the total IP numbers, Class B is 25%, and Class C is approximately 12% 🤯 Here's the current allocation of IP network numbers in Table 1:

                   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, so 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 the IR for allocation to distributed regional registries. Where there are no designated regional registries in a geographic area, the IR will assign addresses to networks in that area according to the Class C allocation divisions 🌈

A preliminary look at the Class C network numbers shows that the prefixes 192 and 193 are assigned, and the rest of the 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 stay unallocated and unassigned until further notice 🛑

The remaining Class C network number space will be allocated in a way that's compatible with potential address aggregation techniques ✨ The plan is to divide this range into eight equally sized address blocks:

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's proposed that a broad geographic allocation be used for these blocks. Right now there are four major areas of address allocation: Europe, North America, Pacific Rim, and South & Central America 🌎 Specifically, the top-level block allocation should 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's proposed that the IR, and any designated regional registries, allocate addresses in line with this overall scheme 💖 Where qualifying regional registries are established, primary responsibility for allocation from within that block will be delegated to that registry.

The ranges labeled "Others" leave room for network number assignments outside the geographic regions already allocated 🦋 The multi-regional range holds network numbers that were assigned before this plan was put in place. The IANA and the IR are proposed to adopt these divisions of the Class C network number space and start assigning network numbers accordingly 🎀

4.0 Assignment of the Network Number Space 🔥

Exhaustion of the IP address space is a big concern for the entire Internet community 😭 This plan for assigning Class A, B, or C IP numbers to network subscribers has two major goals:

• 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 way that's 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 it's also the class of network numbers that's most sparsely populated 🌌 There are only about 77 unassigned Class A network numbers, and those 77 represent about 30% of the total network number space.

The IANA will keep sole responsibility for assigning 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) 🔒 No new Class A assignments are expected in the near future, but any organization petitioning the IANA for a Class A network number is 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 🧡

Organizations used to be recommended to use a subnetted Class B network number rather than multiple Class C network numbers. Because Class B numbers are scarce and most organizations don't use the Class B space well, the recommendation is now to use multiple Class Cs where practical 🙌

The IANA and the IR will keep sole responsibility for the Class B number space. Where there are designated regional registries, those registries act in an auxiliary capacity when 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 meeting this profile will keep growing, and that a Class B network number will allow for that growth and reasonable use of the assigned space 📈 There may be situations where it's impossible to use a block of Class C network numbers in place of a Class B. Those situations will be considered case by case 🌸

4.3. Class C ✨

okay so bestie, this section is about how the Class C space gets handed out 🎀 The big picture: Section 3 of this document suggests splitting up the Class C number space, and that split is mostly an admin thing 💅 It sets the stage for distributed network number registries 🌸 This section is just about how network numbers get assigned from inside those blocks. Sub-allocating blocks to sub-registries is out of scope for this paper, so we're skipping that 🙈

By default, if an organization needs more than a single Class C, it gets a bit-wise contiguous block from the Class C space set aside for its geographic region 🦋

Here's an example, it's giving geography 🌍 A European org that needs fewer than 2048 unique IP addresses but more than 1024 would get 8 contiguous Class C network numbers from the space reserved for European networks, 194.0.0.0 - 195.255.255.255 ✨ Now an org from Central America that needs fewer than 512 unique IP addresses but more than 256 would get 2 contiguous Class C network numbers from the space reserved for Central/South American networks, 200.0.0.0 - 201.255.255.255 🫶

The IR, or whichever registry the IR has delegated the registration function to, decides how many Class C network numbers a subscriber gets, based on these 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 a subscriber says it needs should be based on a 24 month projection 🔮

The maximal block of Class C nets that should be assigned to one subscriber is sixteen contiguous Class C networks, which matches a single IP prefix that is twelve bits long 👑 If a subscriber needs more than 4096 unique IP addresses, they should most likely get a Class B net number instead 🌈

5.0. Conclusion 🌸

Okay this part is kind of a plot twist 😭 Handing out lots of Class C numbers helps keep Class A and B numbers scarce, but it's going to speed up the explosion of routing information that Internet routers have to carry 💀 That means the design assumes the technology will change to handle way more network address assignments, since Class A and B assignments go down and Class C assignments go up 💜

A lot of proposals have been made to deal with how fast network assignments are growing 🦋 Talking through those proposals is beyond the scope and intent of this paper, so we're leaving it there ✨

Real talk: these recommendations for managing the current IP network number space only aim to delay depletion of the IP address space, not to postpone it forever 😭🫶

6.0. Acknowledgements 🎀

The author wants to shout out the Federal Engineering Planning Group (FEPG) and the International Engineering Planning Group (IEPG) for their huge contributions 👑 This document also reflects lots of ideas from the IETF Addressing BOF that happened in Cambridge, MA in July 1992 🌸 Jon Postel (ISI) and Yakov Rekhter (T.J. Watson Research Center, IBM Corp.) reviewed the document and helped shape its content 💅 The author thanks everyone in those groups and everyone who has 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.

[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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