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Applicability Statement for the Implementation of Classless Inter-Domain Routing (CIDR) (RFC1517) Disclosure Number: IPCOM000002347D
Original Publication Date: 1993-Sep-01
Included in the Prior Art Database: 2019-Feb-13
Document File: 4 page(s) / 5K

Publishing Venue

Internet Society Requests For Comment (RFCs)

Related People

Internet Engineering Steering Group: AUTHOR [+1]

Related Documents

10.17487/RFC1517: DOI


Classless Inter-Domain Routing (CIDR) defines a mechanism to slow the growth of routing tables and reduce the need to allocate new IP network numbers. [STANDARDS-TRACK]

This text was extracted from a PDF file.
This is the abbreviated version, containing approximately 47% of the total text.

Network Working Group Internet Engineering Steering Group Request for Comments: 1517 R. Hinden, Editor Category: Standards Track September 1993

Applicability Statement for the Implementation of Classless Inter-Domain Routing (CIDR)

Status of this Memo

This RFC specifies an Internet standards track protocol for the Internet community, and requests discussion and suggestions for improvements. Please refer to the current edition of the "Internet Official Protocol Standards" for the standardization state and status of this protocol. Distribution of this memo is unlimited.

1. Introduction

As the Internet has evolved and grown in recent years, it has become clear that it will soon face several serious scaling problems. These include:

- Exhaustion of the class-B network address space. One fundamental cause of this problem is the lack of a network class of a size that is appropriate for a mid-sized organization. Class-C, with a maximum of 254 host addresses, is too small, while class-B, which allows up to 65534 addresses, is too large to be densely populated. The result is inefficient utilization of class-B network numbers.

- Routing information overload. The size and rate of growth of the routing tables in Internet routers is beyond the ability of current software (and people) to effectively manage.

- Eventual exhaustion of IP network numbers.

It has become clear that the first two of these problems are likely to become critical in the near term. Classless Inter-Domain Routing (CIDR) ttempts to deal with these problems by defining a mechanism to slow the growth of routing tables and reduce the need to allocate new IP network numbers. It does not attempt to solve the third problem, which is of a more long-term nature, but instead endeavors to ease enough of the short to mid-term difficulties to allow the Internet to continue to function efficiently while progress is made on a longer- term solution.

The IESG, after a thorough discussion in the IETF, in June 1992 selected CIDR as the solution for the short term routing table

IESG [Page 1]

RFC 1517 CIDR Applicability Statement September 1993

explosion problem [1].

2. Components of the Architecture

The CIDR architecture is described in the following documents:

- "An Architecture for IP Address Allocation with CIDR" [2]

- "Classless Inter-Domain Routing (CIDR): An Address Assignment and Aggregation Strategy" [3]

The first of these documents presents the overall architecture of CIDR; the second describes the specific address allocation scheme to be used.

In addition to these two documents, "Guidelines for Management of IP Address Space" [4] provides specific recommendations for assigning IP addresses that are consistent with [2] and [3], and "Status of CIDR Deployment in the Internet" [5] describes the timetable for deploying [4] in the Internet. Both [4] and [5] should be viewed as supporting, rather than defining, documents.

In addition to the documents mentioned above, CIDR requires that inter-domain ro...