rfc1917.txt

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RFC 1917      Appeal to Return Unused IP Networks to IANA  February 1996


   Several Internet service providers were given blocks of the Class B
   address space to distribute to customers.  This space was often
   provided to clients based upon a level of service purchased rather
   than actual need.

   Many organizations have either merged or are associated with parent
   organizations which produce situations with large inefficiencies in
   address assignment.

   Many organizations have requested addresses based on their need to
   run TCP/IP on internal machines which have no interest in connecting
   to the global Internet.  Most vendors manuals have instructed (and
   provided copies of the application forms), sites to request IP
   address assignments.

   Other organizations have large internal IP networks, and are
   connected to the Internet through application layer gateways or
   network address translators, and will never announce their internal
   networks.

4. Appeal

   To the members of the Internet community who have IP network
   assignments which may be currently unused, the Internet community
   would like to encourage you to return those addresses to the IANA or
   your provider for reapportionment.

   Specifically those sites who have networks which are unused are
   encouraged to return those addresses. Similarly to those sites who
   are using a small percentage of their address space and who could
   relatively easily remove network assignments from active use, the
   Internet community encourages such efforts.

   To those sites who have networks which will never need to connect to
   the global Internet, or for security reasons will always be isolated,
   consider returning the address assignments to the IANA or your
   provider and utilizing prefixes recommended in RFC 1597.

   In those cases where renumbering is required, sites are encouraged to
   put into place a plan to renumber machines, as is reasonably
   convenient, and work towards minimizing the number of routes
   advertised to their providers.

4.1 Suggestions to Providers

   Many providers are currently advertising non-CIDR routes which
   encompass a large block of addresses, ie any Class A (0/1) or Class B
   (128/2) space.  Some customers who are only using a percentage of



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RFC 1917      Appeal to Return Unused IP Networks to IANA  February 1996


   their address space (assuming they are subnetting using contiguous
   bits) may be willing to allow usage of the upper portion of their
   assigned address space by their providers other customers.

   This scheme requires certain elements be installed or already in
   place to get the routing correct, but has the potential to gain the
   use of a large number of small networks without growth of the global
   routing tables.  This would require additional measures of
   cooperation between providers and their customers but could prove to
   have both economic advantages, as well as good Internet citizen
   standing.

   For example, large organization S has been assigned the class A block
   of addresses 10.0.0.0. and is currently using provider P for their
   connection to the global Internet.  P is already advertising the
   route for 10.0.0.0 to the global Internet.  S has been allocating its
   internal networks using a right to left bit incrementing model.  P
   and S could agree that S will allow some /18 (for example) prefixes
   to be made available for P's other customers.  This would impose no
   hardships whatsoever on S, presuming his router can speak BGP, and
   allow P to attach a huge number of small customers without the need
   to advertise more routes or request additional address blocks from
   the IANA or their upstream provider.

   The "Net 39" experiment as outlined in RFC 1797 and summarized in RFC
   1879 provided practical data on the implementation of the suggested
   schemes.

   Additionally, providers are encouraged to release all unused networks
   which fall outside of their normal address blocks back to the IANA or
   the appropriate registry.

   New customers, particularly those who may have recently changed
   providers, and who have small networks which are not part of
   CIDR'ized blocks, should be encouraged to renumber and release their
   previous addresses back to the provider or the IANA.

   Since the first introduction of CIDR in April of 1994, many providers
   have aggresively pursued the concepts of aggregation.  Some providers
   actively persuaded their customers to renumber, while others pursued
   peering arrangements with other providers, and others did both.
   Providers should continue to actively and routinely pursue both
   methods to streamline routing table growth.  Cooperation between
   providers is absolutely essential to short (and long) term management
   of routing requirements.






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RFC 1917      Appeal to Return Unused IP Networks to IANA  February 1996


   Providers should regularly verify the routes they are advertising to
   their upstream provider(s) to validate their router configurations
   and confirm correct aggregation is occuring.

4.2 Suggestions to the IANA and Address Registries

   In cases where addresses are returned to the IANA, or any other
   address registry, which fits into another registry or providers
   block, the addresses should be turned over to the appropriate
   authority.  This will help maximize the availability of addresses and
   minimize routing table loads.

4.3 How to Return a Block of Address Space to the IANA

   Send the following form to [e-mail] & [e-mail],
   changing the $NET_PREFIX to the network being returned.

   ----------------------------------------------------------------

   Please update the contact information on the following net as
   follows:

   Netname: RESERVED
   Netnumber: $NET_PREFIX

   Coordinator:
     Reynolds, Joyce K.  (JKR1)  [e-mail]
     [phone]
   Alternate Contact:
     Postel, Jon  (JBP)  [e-mail]
     [phone]

   ----------------------------------------------------------------

4.4 How to Return a Block of Address Space to another Address
    Registry

   Each registry will have its own forms and addresses.  Please contact
   the appropriate registry directly.

5. Conclusion

   Rationalizing the global addressing hierarchy is a goal which should
   be supported by any organization which is currently connected or
   plans to connect to the Internet.  If (and possibly when) the
   situation ever reaches a critical point, the core service providers
   whose routers are failing and losing routes will be forced to make
   one of two choices, both painful to the user community.



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RFC 1917      Appeal to Return Unused IP Networks to IANA  February 1996


   They could begin blocking routes to their customers who are
   advertising too many disjoint routes, where "too many" will be set at
   the level necessary to keep their routers functioning properly.  This
   is a domino effect since the next level of providers will be forced
   to make the same effort, until individual organizations are forced to
   only advertise routes to portions of their networks.

   The second option the core providers have is to charge for advertised
   routes.  The price level will be set at a point which reduces the
   number of routes to a level which will keep their routers functioning
   properly.  Once again a domino effect will take place until the price
   increases will effect individual organizations.

   Some planning and efforts by organizations and providers now while
   there is a some time available can help delay or prevent either or
   the two scenarios from occurring.

   This system has already produced very favorable results when applied
   on a small scale.  As of this writing 4 Class A networks have been
   returned to the IANA.  This may not seem significant but those 4
   networks represent over 1.5% of the total IPv4 address capacity.

6. References

        1.  Gerich, E., "Guidelines for Management of the IP
            Address Space", RFC 1466, May 1993.

        2.  Topolcic, C., "Status of CIDR Deployment in the
            Internet", RFC 1467, August 1993.

        3.  Rekhter, Y., and T. Li, "An Architecture for IP Address
            Allocation with CIDR", RFC 1518, September 1993.

        4.  Fuller, V., Li, T., Yu, J., and K. Varadhan, "Classless
            Inter-Domain Routing (CIDR): an Address Assignment
            and Aggregation Strategy", RFC 1519, September 1993.

        5.  Rekhter, Y., Moskowitz, R., Karrenberg, D., and de
            Groot, G., "Address Allocation for Private Internets",
            RFC 1597, March 1994.

        6.  Lear, E., Fair, E., Crocker, D., and T. Kessler,
            "Network 10 Considered Harmful (Some Practices Shouldn't
            be Codified)", RFC 1627, July 1994.

        7.  Huitema, C., "The H Ratio for Address Assignment
            Efficiency", RFC 1715, November 1994.




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RFC 1917      Appeal to Return Unused IP Networks to IANA  February 1996


        8.  IANA, Class A Subnet Experiment, RFC 1797, April
            1995.

7. Security Considerations

   Security issues are not discussed in this memo.

8. Acknowledgements

   I would like to thank the members of the CIDRD mailing list and
   working groups for their suggestion and comments on this document.
   Specific thanks should go to Michael Patton, Tony Li, Noel Chiappa,
   and Dale Higgs for detailed comments and suggestions.

9. Author's Address

   Philip J. Nesser II
   Nesser & Nesser Consulting
   16015 84th Avenue N.E.
   Bothell, WA 98011-4451

   Phone: [phone]
   Fax: [phone]
   EMail: [e-mail]



























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