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Internet Registry IP Allocation Guidelines

The information below is for an old version of the document that is already published as an RFC.
Document Type
This is an older version of an Internet-Draft that was ultimately published as RFC 2050.
Authors Kim Hubbard, Dr. Jon Postel , Mark Kosters , Daniel Karrenberg , David R. Conrad
Last updated 2013-08-25 (Latest revision 1996-08-13)
RFC stream Legacy stream
Intended RFC status (None)
Stream Legacy state (None)
Consensus boilerplate Unknown
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IESG IESG state Became RFC 2050 (Historic)
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Send notices to (None)
K. Hubbard
                                                     M. Kosters
                                                     D. Conrad
                                                     D. Karrenberg
                                                     July 1996


Status of this Memo

     This memo provides information for the Internet community.  
     This memo does not specify an Internet standard of any kind.  
     Distribution of this memo is unlimited.

     This document is an Internet-Draft.  Internet-Drafts are working
     documents of the Internet Engineering Task Force (IETF), its
     areas, and its working groups.  Note that other groups may also
     distribute working documents as Internet-Drafts.

     Internet-Drafts are draft documents valid for a maximum of six
     months and may be updated, replaced, or obsoleted by other
     documents at any time.  It is inappropriate to use Internet-
     Drafts as reference material or to cite them other than as
     ``work in progress.''
     To learn the current status of any Internet-Draft, please check
     the ``1id-abstracts.txt'' listing contained in the Internet-
     Drafts Shadow Directories on (Africa), (Europe), (Pacific Rim), (US East Coast), or (US West Coast).


This document describes the registry system for the distribution of
globally unique Internet address space and registry operations.
Particularly this document describes the rules and guidelines
governing the distribution of this address space.

This document replaces RFC 1466, with all the guidelines and
procedures updated and modified in the light of experience.

This document does not describe private Internet address space and
multicast address space.  It also does not describe regional and local
refinements of the global rules and guidelines.

This document can be considered the base set of operational guidelines
in use by all registries.  Additional guidelines may be imposed by a
particular registry as appropriate.

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Expire in six months

Table of Contents

    1.  Introduction.......................................3

    2.  Allocation Framework...............................4
    2.1  Guidelines for Internet Service Providers.........4
    2.2  Submission of Reassignment Information............7

    3.   Assignment Framework..............................7
    3.1  Common Registry Requirements......................8
    3.2  Network Engineering Plans.........................9
    3.3  Previous Assignment History.......................10
    3.4  Network Deployment Plans..........................10
    3.5  Organization Information..........................10
    3.6  Expected Utilization Rate.........................10

    4.   Operational Guidelines for Registries.............10

    5.   In-Addr.Arpa Domain Maintenance...................12

    6.   Right to Appeal...................................12

    7.   References........................................12

    8.   Authors' Addresses................................13

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                            1. Introduction

The addressing constraints described in this document are
largely the result of the interaction of existing router
technology, address assignment, and architectural history.
After extensive review and discussion, the authors of this
document, the IETF working group that reviewed it and the IESG
have concluded that there are no other currently deployable
technologies available to overcome these limitations. In the
event that routing or router technology develops to the point
that adequate routing aggregation can be achieved by other
means or that routers can deal with larger routing and more
dynamic tables, it may be appropriate to review these

Internet address space is distributed according to the following
three goals:

1) Conservation: Fair distribution of globally unique Internet address
space according to the operational needs of the end-users and Internet
Service Providers operating networks using this address space.
Prevention of stockpiling in order to maximize the lifetime of the
Internet address space.

2) Routability: Distribution of globally unique Internet addresses
in a hierarchical manner, permitting the routing scalability of
the addresses. This scalability is necessary to ensure proper
operation of Internet routing, although it must be stressed that
routability is in no way guaranteed with the allocation or
assignment of IPv4 addresses.

3) Registration: Provision of a public registry documenting address
space allocation and assignment.  This is necessary to ensure
uniqueness and to provide information for Internet trouble shooting
at all levels.

It is in the interest of the Internet community as a whole that the
above goals be pursued.  However it should be noted that
"Conservation" and "Routability" are often conflicting goals.  All
the above goals may sometimes be in conflict with the interests of
individual end-users or Internet service providers.  Careful analysis
and judgement is necessary in each individual case to find an
appropriate compromise.

The Internet Registry system

In order to achieve the above goals the Internet Registry (IR) hierarchy
was established.

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The Internet Registry hierarchy consists of the following levels of
hierarchy as seen from the top down: IANA, Regional IRs, Local IRs.


The Internet Assigned Numbers Authority has authority over all number
spaces used in the Internet.  This includes Internet Address Space. IANA
allocates parts of the Internet address space to regional IRs according
to its established needs.

Regional IRs

Regional IRs operate in large geopolitical regions such as continents.
Currently there are three regional IRs established; InterNIC serving
North America, RIPE NCC serving Europe, and AP-NIC serving the Asian
Pacific region.  Since this does not cover all areas, regional IRs also
serve areas around its core service areas.  It is expected that the
number of regional IRs will remain relatively small.  Service areas will
be of continental dimensions.

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Regional IRs are established under the authority of the IANA.  This
requires consensus within the Internet community of the region.  A con-
sensus of Internet Service Providers in that region may be necessary to
fulfill that role.

The specific duties of the regional IRs include coordination and
representation of all local IRs in its respective regions.

Local IRs

Local IRs are established under the authority of the regional IR and
IANA.  These local registries have the same role and responsibility as
the regional registries within its designated geographical areas.  These
areas are usually of national dimensions.

                        2.  Allocation Framework

2.1  Guidelines for Internet Service Providers (ISPs)

This document makes a distinction between the allocation of IP addresses
and the assignment of IP addresses.  Addresses are allocated to ISPs by
regional registries to assign to its customer base.

ISPs who exchange routing information with other ISPs at multiple loca-
tions and operate without default routing may request space directly
from the regional registry in its geographical area.  ISPs with no
designated regional registry may contact any regional registry and the
regional registry may either handle the request or refer the request to
an appropriate registry.

To facilitate hierarchical addressing, implemented using Classless
Inter-Domain Routing (CIDR), all other ISPs should request address space
directly from its upstream provider.  ISPs only request address space
directly from regional registries if their immediate requirement, when
satisfied with a contiguous block allocation, has a reasonable probabil-
ity of being routable on the Internet, and they meet one or more of the
following conditions.

       a)  the ISP is directly connected to a major routing exchange
           (for purposes of this document, a major routing exchange
            is defined as a neutral layer 2 exchange point connecting
            four or more unrelated ISPs.)

       b)  the ISP is multi-homed, that is, it has more than one
           simultaneous connection to the global Internet and no
           connection is favored over the other

   Note that addresses issued directly from the IRs, (non-provider

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   are the least likely to be routable across the Internet.

The following are the IP allocation guidelines for ISPs:

1.     CIDR addresses are allocated to ISPs in blocks.  It is
       recommended that those blocks remain intact.  Fragmentation of
       CIDR blocks is discouraged.  More specifically, ISPs are
       encouraged to treat address assignments as loans for the
       duration of the connectivity provision.  At the termination
       of the Internet connectivity contract, e.g., the customer
       moves to another service provider, it is recommended the
       customer return the network addresses currently in use and
       renumber into the new provider's address space.  The ISP
       should allow sufficient time for the renumbering process to be
       completed before the IP addresses are reused.

2.     To ensure efficient implementation and use of Classless
       Inter-Domain Routing (CIDR), the Regional Registries issue
       address space on appropriate "CIDR-supported" bit boundaries.

3.     ISPs are required to utilize address space in an efficient
       manner.  To this end, ISPs should have documented
       justification available for each assignment.  The regional
       registry may, at any time, ask for this information.  If the
       information is not available, future allocations may be impacted.
       In extreme cases, existing loans may be impacted.

4.     IP addresses are allocated to ISPs using a slow-start
       procedure.  New ISPs will receive a minimal amount based
       on immediate requirement.  Thereafter,  allocated blocks may be
       increased based on utilization verification supplied to the
       regional registry.  The parent registries are responsible for
       determining appropriate initial and subsequent allocations.
       Additional address allocations will provide enough address space
       to enable the ISP to assign addresses for three months
       without requesting additional address space from its parent
       registry.  Please note that projected customer base has little
       impact on the address allocations made by the parent registries.
       Initial allocation will not be based on any current or future
       routing restrictions but on demonstrated requirements.

 5.    Due to the requirement to increase the utilization efficiency
       of IPv4 address space, all assignments are made with the
       assumption that sites make use of variable length subnet mask
       (VLSM) and classless technologies within their network.  Any
       request for address space based on the use of classfull
       assumptions will require a detailed justification.  The use of

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       classfull technologies for the purposes of administrative
       convenience is generally insupportable due to the limited
       availability of free IPv4 address space.

 6.    Regional registries may set a maximum limit on assignment sizes
       such that a second opinion of the regional registry is required.

 7.    Due to constraints on the available free pool of IPv4 address
       space, the use of static IP address assignments (e.g., one
       address per customer) for dial-up users is strongly discouraged.
       While it is understood that the use of static addressing may
       ease some aspects of administration, the current rate of
       consumption of the remaining unassigned IPv4 address space does
       not permit the assignment of addresses for administrative ease.
       Organizations considering the use of static IP address assignment
       are expected to investigate and implement dynamic assignment
       technologies whenever possible.

2.2  Submission of Reassignment Information

 It is imperative that reassignment information be submitted in a prompt
 and efficient manner to facilitate database maintenance and ensure
 database integrity.  Therefore, assignment information must be
 submitted to the regional registry immediately upon making the
 assignment.  The following reasons necessitate transmission of the
 reassignment information:

       a)  to provide operational staff with information on who is using
           the network number and to provide a contact in case of
           operational/ security problems,

       b)  to ensure that a provider has exhausted a majority of its
           current CIDR allocation, thereby justifying an additional

       c)  to assist in IP allocation studies.

 Procedures for submitting the reassignment information will be
 determined by each regional registry based on its unique requirements.

 All sub-registries (ISPs, Local registries, etc.) must register with
 their respective regional registry to receive information regarding
 reassignment guidelines.  No additional CIDR blocks will be
 allocated by the regional registry or upstream providers until
 approximately 80% of all reassignment information has been submitted.

                        3. Assignment Framework

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An assignment is the delegation of authority over a block of IP
addresses to an end enterprise.   The end enterprise will use addresses
from an assignment internally only; it will not sub-delegate those
addresses.  This section discusses some of the issues involved in
assignments and the framework behind the assignment of addresses.

In order for the Internet to scale using existing technologies, use of
regional registry services should be limited to the assignment of IP
addresses for organizations meeting one or more of the following condi-

      a)  the organization has no intention of connecting to
          the Internet-either now or in the future-but it still
          requires a globally unique IP address.  The organization
          should consider using reserved addresses from RFC1918.
          If it is determined this is not possible, they can be
          issued unique (if not Internet routable) IP addresses.

      b)  the organization is multi-homed with no favored connection.

      c)  the organization's actual requirement for IP space is
          very large, for example, the network prefix required to
          cover the request is of length /18 or shorter.

 All other requestors should contact its ISP for address
 space or utilize the addresses reserved for non-connected networks
 described in RFC1918 until an Internet connection is established.
 Note that addresses issued directly from the IRs,(non-provider based),
 are the least likely to be routable across the Internet.

3.1  Common Registry Requirements

Because the number of available IP addresses on the Internet is limited,
the utilization rate of address space will be a key factor in network
number assignment.  Therefore, in the best interest of the Internet as a
whole, specific guidelines have been created to govern the assignment of
addresses based on utilization rates.

Although topological issues may make exceptions necessary, the basic
criteria that should be met to receive network numbers are listed below:

                25% immediate utilization rate
                50% utilization  rate within 1 year

The utilization rate above is to be used as a guideline, there may be be
occasions when the 1 year rate does not fall exactly in this range.
Organizations must exhibit a high confidence level in its 1 year utili-
zation rate and supply documentation to justify the level of confidence.

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Organizations will be assigned address space based on immediate utiliza-
tion plus 1 year projected utilization.  A prefix longer than /24 may be
issued if deemed appropriate.  Organizations with less than 128 hosts
will not be issued an IP address directly from the IRs.  Organizations
may be issued a prefix longer than /24 if the organization can provide
documentation from a registry recognized ISP indicating the ISP will
accept the long prefix for injection into the global routing system.

Exceptions to the criteria will not be made based on insufficient equip-
ment without additional detailed justification.  Organizations should
implement variable length subnet mask (VLSM) internally to maximize the
effective utilization of address space.  Address assignments will be
made under the assumption that VLSM is or will be implemented.

IP addresses are valid as long as the criteria continues to be met. The
IANA reserves the right to invalidate any IP assignments once it is
determined the the requirement for the address space no longer exists.
In the event of address invalidation, reasonable efforts will be made by
the appropriate registry to inform the organization that the addresses
have been returned to the free pool of IPv4 address space.

3.2  Network Engineering Plans

Before a registry makes an assignment, it must examine each address
space request in terms of the requesting organization's networking
plans.  These plans should be documented, and the following information
should be included:

      1.  subnetting plans, including subnet masks and number of
          hosts on each subnet for at least one year

      2.  a description of the network topology

      3.  a description of the network routing plans, including the
          routing protocols to be used as well as any limitations.

 The subnetting plans should include:

      a)  a tabular listing of all subnets on the network

      b)  its associated subnet masks

      c)  the estimated number of hosts

      d)  a brief descriptive remark regarding the subnet.

If subnetting is not being used, an explanation why it cannot be imple-
mented is required.  Care must be taken to ensure that the host and

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subnet estimates correspond to realistic requirements and are not based
on administrative convenience.

3.3  Previous Assignment History

To promote increased usage of address space, the registries will require
an accounting of address space previously assigned to the enterprise, if
any.  In the context of address space allocation, an "enterprise" con-
sists of all divisions and/or subsidiaries falling under a common parent
organization.  The previous assignment history should include all net-
work numbers assigned to the organization, plus the network masks for
those networks and the number of hosts on each (sub-)network.  Suffi-
cient corroborating evidence should be provided to allow the assigning
registry to be confident that the network descriptions provided are
accurate.  Routing table efficiency will be taken into account by the
regional registries and each request will be handled on a case by case

3.4  Network Deployment Plans

In order to assign an appropriate amount of space in the required time
frame, a  registry  may request deployment plans for a network.  Deploy-
ment plans should include the number of hosts to be deployed per time
period, expected network growth during that time period, and changes in
the network topology that describe the growth.

3.5  Organization Information

A registry may request that an organization furnish a published descrip-
tion verifying that the organization is what it claims to be.  This
information can consist of brochures, documents of incorporation, or
similar published material.

3.6  Expected Utilization Rate

As stated in the foregoing text, one of the key factors in determining
how much address space is appropriate for an organization is the
expected utilization rate of the network.  The expected utilization rate
is the number of hosts connected to the network divided by the total
number of hosts possible on the network.  In addition, the estimated
number of hosts should be projected over a reasonable time frame, i.e.,
one in which the requesting enterprise has a high level of confidence.
The minimal utilization rate is set by the IANA and may be changed at
any time.  New utilization rates may be enforced by the regional regis-
tries prior to updating the written policy.

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               4.  Operational Guidelines For Registries

1.     Regional Registries provide registration services as its
       primary function.  Therefore, regional registries may charge some
       fee for services rendered, generally in relation to the cost of
       providing those services.

2.     Regardless of the source of its address space, sub-registries
       (Local IRs, ISPs, etc.) must adhere to the guidelines of its
       regional registry.  In turn, it must also ensure that its
       customers follow those guidelines.

3.     To maximize the effective use of address space, IP addresses need
       to be assigned/allocated in classless blocks.  With this in mind,
       assignments will not be made in Class Cs or Bs but by prefix
       length.  Consequently, an organization that would have been
       assigned a Class B in the past will now be assigned a /16 prefix,
       regardless of the actual address class.

4.     All IP address requests are subject to audit and verification
       by any means deemed appropriate by the regional registry.
       If any assignment is found to be based on false information,
       the registry may invalidate the request and return the
       assigned addresses back to the pool of free addresses for
       later assignment.

5.     Due to technical and implementation constraints on the Internet
       routing system and the possibility of routing overload, major
       transit providers may need to impose certain restrictions to
       reduce the number of globally advertised routes.  This may
       include setting limits on the size of CIDR prefixes added to
       the routing tables, filtering of non-aggregated routes, etc.
       Therefore, addresses obtained directly from regional registry
       (provider-independent, also known as portable) are not
       guaranteed routable on the Internet.

6.     Information provided to request address space is often considered
       sensitive by the requesting  organization.  The assigning
       registry must treat as confidential any and all information
       that the requesting organization specifically indicates as
       sensitive.  When a requesting organization does not have
       assurance of privacy, the parent of the assigning registry may
       be required to do the assignment.  In such cases, the parent
       registry will provide the assigning registry with information
       regarding the appropriate amount of address space to allocate.

7.    The transfer of IP addresses from one party to another must be
      approved by the regional registries.  The party trying to obtain

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      the IP address must meet the same criteria as if they were
      requesting an IP address directly from the IR.

                  5.  In-ADDR.ARPA Domain Maintenance

The regional registries will be responsible for maintaining IN-ADDR.ARPA
records only on the parent blocks of IP addresses issued directly to the
ISPs or those CIDR blocks of less than /16.  Local IRs/ISPs with a pre-
fix length of /16 or shorter will be responsible for maintaining all
IN-ADDR.ARPA resource records for its customers.

IN-ADDR.ARPA resource records for networks not associated with a
specific provider will continue to be maintained by the regional regis-

                          6.  Right to Appeal
If an organization feels that the registry that assigned its address has
not performed its task in the requisite manner, the organization has the
right of appeal to the parent registry.

In such cases, the assigning registry shall make available all relevant
documentation to the parent registry, and the decision of the parent
registry shall be considered final (barring additional appeals to the
parent registry's parent).  If necessary, after exhausting all other
avenues, the appeal may be forwarded to IANA for a final decision.  Each
registry must, as part of their policy, document and specify how to
appeal a registry assignment decision.

                             7.  References

[RFC 1519] V. Fuller, T. Li, J. Yu, K. Varadhan,
   "Classless Inter- Domain Routing (CIDR): an Address
   Assignment and Aggregation Strategy".

[RFC 1518] Y. Rekhter, T. Li, "An Architecture for IP
   Address Allocation with CIDR".

[RFC 1918] Y. Rekhter, B. Moskowitz, D. Karrenberg, G. de Groot,
 "Address Allocation for Private Internets".

[RFC 1814] E. Gerich, "Unique Addresses are Good"

[RFC 1900] B. Carpenter, Y. Rekhter, "Renumbering Needs Work"

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8. Authors' Addresses

    Kim Hubbard
    InterNIC Registration Services
    c/o Network Solutions
    505 Huntmar Park Drive
    Herndon, VA 22070
    Phone: (703) 742-4870

    Jon Postel
    USC/Information Sciences Institute
    4676 Admiralty Way
    Marina del Rey, CA  90292
    Phone: 310-822-1511
    EMail: Postel@ISI.EDU

    Mark Kosters
    InterNIC Registration Services
    c/o Network Solutions
    505 Huntmar Park Drive
    Herndon, VA 22070
    Phone: (703) 742-4795

    David Conrad
    Asia Pacific Network Information Center
    c/o United Nations University
    53-70 Jingumae 5-chome,
    Shibuya-ku, Tokyo 150
    Phone: +81-3-5467-7014
    email: davidc@APNIC.NET

    Daniel Karrenberg
    Kruislaan 409
    SJ Amsterdam NL-1098
    Phone: +31 20 592 5065
    email: dfk@RIPE.NET

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