Classless Inter-Domain Routing (CIDR): an Address Assignment and Aggregation Strategy
RFC 1519
Document | Type |
RFC - Proposed Standard
(September 1993; Errata)
Obsoleted by RFC 4632
Obsoletes RFC 1338
Was draft-fuller-cidr-strategy (individual)
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Authors | Vince Fuller , Tony Li , Kannan Varadhan , Jessica Yu | ||
Last updated | 2020-01-21 | ||
Stream | Legacy | ||
Formats | plain text html pdf htmlized with errata bibtex | ||
Stream | Legacy state | (None) | |
Consensus Boilerplate | Unknown | ||
RFC Editor Note | (None) | ||
IESG | IESG state | RFC 1519 (Proposed Standard) | |
Telechat date | |||
Responsible AD | (None) | ||
Send notices to | (None) |
Network Working Group V. Fuller Request for Comments: 1519 BARRNet Obsoletes: 1338 T. Li Category: Standards Track cisco J. Yu MERIT K. Varadhan OARnet September 1993 Classless Inter-Domain Routing (CIDR): an Address Assignment and Aggregation Strategy 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. Abstract This memo discusses strategies for address assignment of the existing IP address space with a view to conserve the address space and stem the explosive growth of routing tables in default-route-free routers. Table of Contents Acknowledgements ................................................. 2 1. Problem, Goal, and Motivation ................................ 2 2. CIDR address allocation ...................................... 3 2.1 Aggregation and its limitations ............................. 3 2.2 Distributed network number allocation ....................... 5 3. Cost-benefit analysis ........................................ 6 3.1 Present allocation figures .................................. 7 3.2 Historic growth rates ....................................... 8 3.3 Detailed analysis ........................................... 8 3.3.1 Benefits of new addressing plan ........................... 9 3.3.2 Growth rate projections ................................... 9 4. Changes to inter-domain routing protocols and practices ...... 11 4.1 Protocol-independent semantic changes ....................... 11 4.2 Rules for route advertisement ............................... 11 4.3 How the rules work .......................................... 13 4.4 Responsibility for and configuration of aggregation ......... 14 4.5 Intra-domain protocol considerations ........................ 15 5. Example of new allocation and routing ........................ 15 Fuller, Li, Yu & Varadhan [Page 1] RFC 1519 CIDR Address Strategy September 1993 5.1 Address allocation .......................................... 15 5.2 Routing advertisements ...................................... 17 6. Extending CIDR to class A addresses .......................... 18 7. Domain Naming Service considerations ......................... 20 7.1 Procedural changes for class-C "supernets" ................... 20 7.2 Procedural changes for class-A subnetting .................... 21 8. Transitioning to a long term solution ........................ 22 9. Conclusions .................................................. 22 10. Recommendations ............................................. 22 11. References .................................................. 23 12. Security Considerations ..................................... 23 13. Authors' Addresses .......................................... 24 Acknowledgements The authors wish to express their appreciation to the members of the ROAD group with whom many of the ideas contained in this document were inspired and developed. 1. Problem, Goal, and Motivation As the Internet has evolved and grown over in recent years, it has become evident that it is soon to face several serious scaling problems. These include: 1. Exhaustion of the class B network address space. One fundamental cause of this problem is the lack of a network class of a size which is appropriate for 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 for most organizations. 2. Growth of routing tables in Internet routers beyond the ability of current software, hardware, and people to effectively manage. 3. Eventual exhaustion of the 32-bit IP address space. It has become clear that the first two of these problems are likely to become critical within the next one to three years. This memo attempts to deal with these problems by proposing a mechanism to slow the growth of the routing table and the need for allocating new IPShow full document text