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Network Working Group K. Hubbard Request for Comments: 2050 M. Kosters Obsoletes: 1466 InterNIC BCP: 12 D. Conrad Category: Best Current Practice APNIC

                                                      D. Karrenberg
                                                          J. Postel
                                                      November 1996

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.

IESG Note:

 By approving this document as a Best Current Practice,the IESG
 asserts its belief that this policy described herein is an accurate
 representation of the current practice of the IP address registries
 with respect to address assignment.  This does not constitute
 endorsement or recommendation of this policy by the IESG. The IESG
 will reevaluate its approval of this document in December 1997 taking
 into consideration the results of the discussions that will be take
 place in the IRE Working Group between now and then.


 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 describes the IP assignment policies currently used by
 the Regional Registries to implement the guidelines developed by the
 IANA. The guidelines and these policies are subject to revision at
 the direction of the IANA. The registry working group (IRE WG) will
 be discussing these issues and may provide advice to the IANA about
 possible revisions.
 This document replaces RFC 1466, with all the guidelines and
 procedures updated and modified in the light of experience.

Hubbard, et. al. Best Current Practice [Page 1] RFC 2050 Internet Registry IP Allocation Guidelines November 1996

 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.

Table of Contents

  1.  Introduction.......................................2
  2.  Allocation Framework...............................4
  2.1  Guidelines for Internet Service Providers.........4
  2.2  Submission of Reassignment Information............6
  3.   Assignment Framework..............................7
  3.1  Common Registry Requirements......................7
  3.2  Network Engineering Plans.........................8
  3.3  Previous Assignment History.......................9
  3.4  Network Deployment Plans..........................9
  3.5  Organization Information..........................9
  3.6  Expected Utilization Rate.........................10
  4.   Operational Guidelines for Registries.............10
  5.   In-Addr.Arpa Domain Maintenance...................11
  6.   Right to Appeal...................................11
  7.   References........................................12
  8.   Security Considerations...........................12
  9.   Authors' Addresses................................13

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 constraints.
 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

Hubbard, et. al. Best Current Practice [Page 2] RFC 2050 Internet Registry IP Allocation Guidelines November 1996

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

Hubbard, et. al. Best Current Practice [Page 3] RFC 2050 Internet Registry IP Allocation Guidelines November 1996

    Regional IRs are established under the authority of the IANA.
    This requires consensus within the Internet community of the
    region.  A consensus 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

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
 ISPs who exchange routing information with other ISPs at multiple
 locations 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 probability 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

Hubbard, et. al. Best Current Practice [Page 4] RFC 2050 Internet Registry IP Allocation Guidelines November 1996

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

Hubbard, et. al. Best Current Practice [Page 5] RFC 2050 Internet Registry IP Allocation Guidelines November 1996

     assumptions will require a detailed justification.  The use of
     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
 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.

Hubbard, et. al. Best Current Practice [Page 6] RFC 2050 Internet Registry IP Allocation Guidelines November 1996

3. Assignment Framework

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

Hubbard, et. al. Best Current Practice [Page 7] RFC 2050 Internet Registry IP Allocation Guidelines November 1996

 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 utilization rate and supply documentation to justify the level
 of confidence.
 Organizations will be assigned address space based on immediate
 utilization 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
 equipment 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
 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.

Hubbard, et. al. Best Current Practice [Page 8] RFC 2050 Internet Registry IP Allocation Guidelines November 1996

 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
 implemented is required.  Care must be taken to ensure that the host
 and 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" consists of all divisions and/or subsidiaries falling
 under a common parent organization.  The previous assignment history
 should include all network numbers assigned to the organization, plus
 the network masks for those networks and the number of hosts on each
 (sub-)network.  Sufficient 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 basis.

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.
 Deployment 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
 description verifying that the organization is what it claims to be.
 This information can consist of brochures, documents of
 incorporation, or similar published material.

Hubbard, et. al. Best Current Practice [Page 9] RFC 2050 Internet Registry IP Allocation Guidelines November 1996

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 registries prior to updating the
 written policy.

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

Hubbard, et. al. Best Current Practice [Page 10] RFC 2050 Internet Registry IP Allocation Guidelines November 1996

     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
     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 prefix 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

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.

Hubbard, et. al. Best Current Practice [Page 11] RFC 2050 Internet Registry IP Allocation Guidelines November 1996

7. References

 [RFC 1519] Fuller, V., Li, T., Yu, J., and K. Varadhan,
    "Classless Inter- Domain Routing (CIDR): an Address
    Assignment and Aggregation Strategy", September 1993.
 [RFC 1518] Rekhter, Y., and T. Li, "An Architecture for IP
    Address Allocation with CIDR", September 1993.
 [RFC 1918] Rekhter, Y., Moskowitz, B., Karrenberg, D., and
    G. de Groot, "Address Allocation for Private Internets",
    February 1996.
 [RFC 1814] Gerich, E., "Unique Addresses are Good", June 1995.
 [RFC 1900] Carpenter, B., and Y. Rekhter, "Renumbering Needs Work",
    February 1996.

8. Security Considerations

 Security issues are not discussed in this memo.

Hubbard, et. al. Best Current Practice [Page 12] RFC 2050 Internet Registry IP Allocation Guidelines November 1996

9. Authors' Addresses

 Kim Hubbard
 InterNIC Registration Services
 c/o Network Solutions
 505 Huntmar Park Drive
 Herndon, VA 22070
 Phone: (703) 742-4870
 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
 Jon Postel
 USC/Information Sciences Institute
 4676 Admiralty Way
 Marina del Rey, CA  90292
 Phone: 310-822-1511
 EMail: Postel@ISI.EDU

Hubbard, et. al. Best Current Practice [Page 13]

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