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  • Network Working Group Y. Rekhter Request for Comments: 1918 Cisco Systems Obsoletes: 1627, 1597 B. Moskowitz BCP: 5 Chrysler Corp. Category: Best Current Practice D. Karrenberg RIPE NCC G. J. de Groot RIPE NCC E. Lear Silicon Graphics, Inc. February 1996 

    Address Allocation for Private Internets

    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.

    1. Introduction

    For the purposes of this document, an enterprise is an entity autonomously operating a network using TCP/IP and in particular determining the addressing plan and address assignments within that network. This document describes address allocation for private internets. The allocation permits full network layer connectivity among all hosts inside an enterprise as well as among all public hosts of different enterprises. The cost of using private internet address space is the potentially costly effort to renumber hosts and networks between public and private.

    2. Motivation

    With the proliferation of TCP/IP technology worldwide, including outside the Internet itself, an increasing number of non-connected enterprises use this technology and its addressing capabilities for sole intra-enterprise communications, without any intention to ever directly connect to other enterprises or the Internet itself. The Internet has grown beyond anyone's expectations. Sustained exponential growth continues to introduce new challenges. One challenge is a concern within the community that globally unique address space will be exhausted. A separate and far more pressing concern is that the amount of routing overhead will grow beyond the Rekhter, et al Best Current Practice [Page 1]

    RFC 1918 Address Allocation for Private Internets February 1996 capabilities of Internet Service Providers. Efforts are in progress within the community to find long term solutions to both of these problems. Meanwhile it is necessary to revisit address allocation procedures, and their impact on the Internet routing system. To contain growth of routing overhead, an Internet Provider obtains a block of address space from an address registry, and then assigns to its customers addresses from within that block based on each customer requirement. The result of this process is that routes to many customers will be aggregated together, and will appear to other providers as a single route [RFC1518], [RFC1519]. In order for route aggregation to be effective, Internet providers encourage customers joining their network to use the provider's block, and thus renumber their computers. Such encouragement may become a requirement in the future. With the current size of the Internet and its growth rate it is no longer realistic to assume that by virtue of acquiring globally unique IP addresses out of an Internet registry an organization that acquires such addresses would have Internet-wide IP connectivity once the organization gets connected to the Internet. To the contrary, it is quite likely that when the organization would connect to the Internet to achieve Internet-wide IP connectivity the organization would need to change IP addresses (renumber) all of its public hosts (hosts that require Internet-wide IP connectivity), regardless of whether the addresses used by the organization initially were globally unique or not. It has been typical to assign globally unique addresses to all hosts that use TCP/IP. In order to extend the life of the IPv4 address space, address registries are requiring more justification than ever before, making it harder for organizations to acquire additional address space [RFC1466]. Hosts within enterprises that use IP can be partitioned into three categories: 

  • Welcome to this ANUK/Unipol Code of Standards for Larger Student Developments on-line training course for persons involved with the management of student accommodation not managed and controlled by educational establishments.