An Appeal to the Internet Community to Return Unused IP Networks (Prefixes) to the IANA
RFC 1917
Document | Type |
RFC - Best Current Practice
(February 1996; No errata)
Also known as BCP 4
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Author | Philip Nesser | ||
Last updated | 2013-03-02 | ||
Stream | Internent Engineering Task Force (IETF) | ||
Formats | plain text html pdf htmlized (tools) htmlized bibtex | ||
Stream | WG state | (None) | |
Document shepherd | No shepherd assigned | ||
IESG | IESG state | RFC 1917 (Best Current Practice) | |
Consensus Boilerplate | Unknown | ||
Telechat date | |||
Responsible AD | (None) | ||
Send notices to | (None) |
Network Working Group P. Nesser II Request for Comments: 1917 Nesser & Nesser Consulting BCP: 4 February 1996 Category: Best Current Practice An Appeal to the Internet Community to Return Unused IP Networks (Prefixes) to the IANA Status of this Memo This document specifies an Internet Best Current Practices for the Internet Community, and requests discussion and suggestions for improvements. Distribution of this memo is unlimited. Abstract This document is an appeal to the Internet community to return unused address space, i.e. any block of consecutive IP prefixes, to the Internet Assigned Numbers Authority (IANA) or any of the delegated registries, for reapportionment. Similarly an appeal is issued to providers to return unused prefixes which fall outside their customary address blocks to the IANA for reapportionment. 1. Background The Internet of today is a dramatically different network than the original designers ever envisioned. It is the largest public data network in the world, and continues to grow at an exponential rate which doubles all major operational parameters every nine months. A common metaphor in engineering is that every time a problem increases in size by an order of magnitude, it becomes a new problem. This adage has been true over the lifetime of the Internet. The Internet is currently faced with two major operational problems (amoung others). The first is the eventual exhaustion of the IPv4 address space and the second is the ability to route packets between the large number of individual networks that make up the Internet. The first problem is simply one of supply. There are only 2^32 IPv4 addresses available. The lifetime of that space is proportional to the efficiency of its allocation and utilization. The second problem is mainly a capacity problem. If the number of routes exceeds the current capacity of the core Internet routers, some routes will be dropped and sections of the Internet will no longer be able to communicate with each other. The two problems are coupled and the dominant one has, and will, change over time. Nesser Best Current Practice [Page 1] RFC 1917 Appeal to Return Unused IP Networks to IANA February 1996 The initial design of IP had all addresses the same, eight bits of network number and twenty four bits of host number. The expectation was of a few, large, global networks. During the first spurts of growth, especially with the invention of LAN technologies, it became obvious that this assumption was wrong and the separation of the address space into three classes (Class A for a few huge networks; Class B for more, smaller networks; and Class C for those really small LANs, with lots of network numbers) was implemented. Soon subnets were added so sites with many small LANs could appear as a single network to others, the first step at limiting routing table size. And finally, CIDR was introduced to the network, to add even more flexibility to the addressing, extending the split from three classes to potentially thirty different classes. Subnets were introduced to provide a mechanism for sites to divide a single network number (Class A, B, or C) into pieces, allowing a higher utilization of address space, and thus promoting conservation of the IPv4 address space. Because of the built-in notion of classful addresses, subnetting automatically induced a reduction in the routing requirements on the Internet. Instead of using two (or more) class C networks, a site could subnet a single class B into two (or more) subnets. Both the allocation and the advertisement of a route to the second and succeeding class C's are saved. Since 1993, the concept of classless (the "C" in CIDR) addresses have been introduced to the Internet community. Addresses are increasingly thought of as bitwise contiguous blocks of the entire address space, rather than a class A,B,C network. For example, the address block formerly known as a Class A network, would be referred to as a network with a /8 prefix, meaning the first 8 bits of the address define the network portion of the address. Sometimes the /8 will be expressed as a mask of 255.0.0.0 (in the same way a 16 bit subnet mask will be written as 255.255.0.0). This scheme allows "supernetting" of addresses together into blocks which can be advertised as a single routing entry. The practical purpose of this effort is to allow service providers and address registries to delegate realistic address spaces to organizations and be unfettered by the traditional network classes, which were inappropriately sized for most organizations. For example the blockShow full document text