rfc1467.txt

<VC++网络游戏建摸与实现>源代码

   marks whose relevance will become apparent below).

   The NSFNET/ANSNET routing database includes only those networks that
   meet the NSF Acceptable Use Policy (AUP) or the ANSNET CO+RE AUP.
   There are a number of networks connected to the Internet that do not
   meet these criteria. Although they are not in the NSFNET/ANSNET
   routing database, they are in the forwarding tables of a number of
   network providers. Currently, the number of networks that are
   connected to other known service providers but are not in the
   NSFNET/ANSNET routing database is significantly smaller than (less
   than 25% of) the number that are in the NSFNET/ANSNET database. There
   is no estimate available for the rate of growth of the number of such
   non-NSFNET/ANSNET networks. It is assumed here that the growth rate
   of these networks is approximately the same as that of AUP networks
   in the NSFNET/ANSNET routing database.

   Analysis of the more than 13K networks in the NSFNET/ANSNET routing
   database, as well as the allocated but unconnected networks, suggests
   that CIDR deployment should have a significant impact on the number
   of forwarding table entries that any router needs to maintain, and
   its rate of growth.  However, an in-depth study was begun at the July
   1993 meeting of the BGP Deployment Working Group of the IETF [5] to
   (among other goals) evaluate the impact of CIDR on the growth rate of
   router forwarding tables.



Topolcic                                                        [Page 5]

RFC 1467       Status of CIDR Deployment in the Internet     August 1993


6. Capacity of deployed networks

   The following paragraphs describe the current occupancy of the
   forwarding tables of the routers of several transit network providers
   and their expected capacities and an estimate of the time when that
   capacity would be reached if the growth rate were to continue as
   today. This list is a subset of all relevant providers, but is
   considered approximately representative of the situation of other
   network providers. It is shown in alphabetical order.

   ALTERNET nodes are Cisco routers, and currently carry approximately
   11K to 12K routes, both AUP and non-AUP. With their current
   configuration, they have enough memory so that they are expected to
   support up to approximately 35K routes.  If the rate at which the
   number of these routes is expected to grow is approximately the same
   as the rate that the NSFNET/ANSNET policy routing database is
   growing, then this number may be reached in late 1994.  However, if
   the growth rate continues unchecked, it is expected that the
   processing capacity of the routers will be surpassed before their
   memory is exhausted. It is expected that CIDR will be in place long
   before this point is reached.

   All ANSNET routers have recently been upgraded to AIX 3.2. This
   version supports up to 12K networks.  These routers currently carry
   only the active networks in the NSFNET/ANSNET routing database.  It
   is anticipated that the next version of router code will be deployed
   before September 1993, the projected date for when there will be 12K
   active networks.  This version will support 25K active networks.
   Although there are no current plans for a version of router code that
   supports more than 25K networks, it is believed that CIDR will help
   this situation.

   EBONE nodes are Cisco routers. They currently carry approximately 10K
   to 11K routes. With their current configuration, they may be able to
   support approximately 40K routes. However, the number of paths may be
   very relevant. The memory required for the BGP table (rather than the
   forwarding table) is a function of the number of paths.  If a new
   transatlantic link were to be added, EBONE could receive all the
   North American routes through it. This would add a new set of paths.
   Each such transatlantic link would increase the memory required by
   approximately 20%. Due to the network topology between North America
   and Europe, new transatlantic links tend to result in new paths, and
   therefore significant memory requirements. It is very difficult to
   predict the addition of future transatlantic links because they
   result from business or political requirements, not bandwidth
   requirements.





Topolcic                                                        [Page 6]

RFC 1467       Status of CIDR Deployment in the Internet     August 1993


   ESNET uses Cisco routers. However, it is already in trouble, but not
   because of the size of the forwarding tables. The problem is its need
   to maintain considerable configuration information describing which
   networks it should or should not accept from its neighbors, and the
   fact that this information must be stored in a non-volatile memory of
   limited size. CIDR aggregation is expected to help this problem.
   Also, ESNET plans to deploy BGP-4 and CIDR only after it is in a full
   release, so does not plan to participate in the initial BGP-4
   deployment. ESNET will upgrade their nodes to Cisco CSC-4's in the
   meantime.

   All SPRINTLINK and ICM nodes have recently been upgraded to Cisco
   CSC-4 routers with 16MB of memory. They will carry full routing,
   including not only the routes that the NSFNET/ANSNET carries, but
   also routes to networks that do not comply with the NSF or CO+RE
   AUPs. The SPRINT routers currently carry approximately 11K to 12K
   routes, and it is expected that they will be able to support up to
   approximately 25K routes, as currently configured. The 25K announced
   network point may be reached in approximately mid-1994. Again, it is
   expected that CIDR deployment will have a significant impact on this
   growth rate, well before this time.

7. Acknowledgements

   This report contains information from a number of sources, including
   vendors, operators, researchers, and organizations that foster
   cooperation in the Internet community. Specific organizations include
   the Intercontinental Engineering and Planning Group (IEPG), the BGP-4
   Deployment Working Group of the IETF, the Federal Networking Council
   (FNC), and the FNC Engineering and Planning Group (FEPG). Specific
   individuals include, in alphabetical order, Arun Arunkumar, Tony
   Bates, Mary Byrne, Bob Collet, Mike Craren, Dennis Ferguson, Tony
   Hain, Elise Gerich, Mark Knopper, John Krawczyk, Tony Li, Peter
   Lothberg, Andrew Partan, Gary Rucinski, Frank Solensky, and Jessica
   Yu. This report would not have been possible without the willingness
   of these people to make their information public for the good of the
   community.

8. References

   [1] Gerich, E., "Guidelines for Management of IP Address Space",
       RFC 1366, Merit, October 1992.

   [2] Gerich, E., "Guidelines for Management of IP Address Space",
       RFC 1466, Merit, May 1993.

   [3] Topolcic, C., "Schedule for IP Address Space Management
       Guidelines", RFC 1367, CNRI, October 1992.



Topolcic                                                        [Page 7]

RFC 1467       Status of CIDR Deployment in the Internet     August 1993



   [4] Fuller, V. et al, "Classless Inter-Domain Routing (CIDR): an
       Address Assignment and Aggregation Strategy", working draft
       obsoleting RFC 1338, BARRNet, February 1993.

   [5] Yu, J., "Minutes of the BGP Deployment Working Group
       (BGPDEPL)", MERIT, July 1993.

   [6] Solensky, F., Internet Growth Charts, "big-internet" mailing
       list, munnari.oz.au:big-internet/nsf-netnumbers-<yymm>.ps

9. Other relevant documents

       Huitema, C., "IAB Recommendation for an Intermediate Strategy
       to Address the Issue of Scaling", RFC 1481, Internet
       Architecture Board, July 1993.

       Knopper, M., "Minutes of the NSFNET Regional Techs Meeting",
       working draft, MERIT, June 1993.

       Knopper, M., and Richardson, S., " Aggregation Support in the
       NSFNET Policy-Based Routing Database", RFC 1482, MERIT, June
       1993.

       Topolcic, C., "Notes of BGP-4/CIDR Coordination Meeting of 11
       March 93", working draft, CNRI, March 1993.

       Rekhter, Y., and Topolcic, C., "Exchanging Routing Information
       Across Provider/Subscriber Boundaries in the CIDR Environment",
       working draft, IBM Corp., CNRI, April 1993.

       Rekhter, Y., and Li, T., "An Architecture for IP Address
       Allocation with CIDR", working draft, IBM Corp., cisco Systems,
       February 1993.

       Gross, P., and P. Almquist, "IESG Deliberations on Routing and
       Addressing", RFC 1380, IESG, November 1992.














Topolcic                                                        [Page 8]

RFC 1467       Status of CIDR Deployment in the Internet     August 1993


10. Security Considerations

   Security issues are not discussed in this memo.

11. Author's Address

   Claudio Topolcic
   Corporation for National Research Initiatives
   895 Preston White Drive, Suite 100
   Reston, VA  22091

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






































Topolcic                                                        [Page 9]