Network Working Group C. Topolcic
Request for Comments: 1467 CNRI
Obsoletes: 1367 August 1993 Status of CIDR Deployment in the Internet
Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard. Distribution of this memo is
This document describes the current status of the development and
deployment of CIDR technology into the Internet. This document
replaces RFC 1367, which was a schedule for the deployment of IP
address space management procedures to support route aggregation.
Since all the milestones proposed in RFC 1367 except for the delivery
and installation of CIDR software were met, it does not seem
appropriate to issue an updated schedule. Rather, this document is
intended to provide information about how this effort is proceeding,
which may be of interest to the community.
The Internet's exponential growth has led to a number of difficulties
relating to the management of IP network numbers. The administrative
overhead of allocating ever increasing volumes of IP network numbers
for global users has stressed the organizations that perform this
function. The volume of IP network numbers that are reachable
through the Internet has taxed a number of routers' ability to manage
their forwarding tables. The poor utilization of allocated IP
network numbers has threatened to deplete the Class A and Class B
During the past few years, a consensus has emerged among the Internet
community in favor of a number of mechanisms to relieve these
problems for the mid-term. These mechanisms are expected to be put
into place in the short term and to provide relief for the mid-term.
Fundamental changes to the Internet protocols to ensure the
Internet's continued long term growth and well being are being
explored and are expected to succeed the mid-term mechanisms.
The global Internet community have been cooperating closely in such
forums as the IETF and its working groups, the IEPG, the NSF Regional
Techs Meetings, INET, INTEROP, FNC, FEPG, and other assemblies in
order to ensure the continued stable operation of the Internet.
Recognizing the need for the mid-term mechanisms and receiving
support from the Internet community, the US Federal Agencies proposed
procedures to assist the deployment of these mid-term mechanisms.
These procedures were originally described in RFC 1366 , which was
recently made obsolete by RFC 1466 . In October 1992, a schedule
was proposed for the implementation of the procedures, described in
RFC 1367 .
2. Milestones that have been met
Most of the milestones of the proposed schedule were implemented on
time. These milestones are shown below, essentially as they appear in
, but with further comment where appropriate:
1) 31 October 92:
The following address allocation procedures were continued:
a) Initial set of criteria for selecting regional address
registries were put into place, and requests from
prospective regional registries were accepted by the
The Reseaux IP Europeens Network Coordination Centre
(RIPE NCC) requested to become a regional registry.
As per the addressing plan of RFC 1366, the RIPE NCC
was given the block 184.108.40.206 to 220.127.116.11 to
administer for the European Internet community. The RIPE
NCC had previously and independently obtained the block
18.104.22.168 to 22.214.171.124. Although this block had been
allocated before RFC 1366, the RIPE NCC was able to manage
it according to the guidelines in RFC 1366.
b) Class A network numbers were put on reserve for possible
future use. The unreserved Class A numbers became very
difficult to obtain.
c) Class B network numbers were issued only when
reasonably justified. Whenever possible, a block of C's
was issued rather than a B. The requirements for
allocating a Class B became progressively more constrained
until the date in step (3).
d) Class C network numbers were allocated according to the
addressing plan of , now obsoleted by . Allocation
continued to be performed by the Internet Registry (IR)
for regions of the world where an appropriate regional
registry had not yet been designated by the IANA.
2) 14 February 93:
The schedule in  was re-evaluated, and there appeared to
be no reason to readjust it, so it was continued as
originally set out.
3) 15 April 93:
a) The IR began to allocate all networks according to the
addressing plan of , now obsoleted by , in
appropriately sized blocks of Class C numbers.
b) Class B network numbers became difficult to obtain,
following the recommendation of the addressing plan and
were only issued when justified.
Furthermore, throughout this time period, network service providers
have requested blocks of network numbers from the Class C address
space for the purpose of further allocating them to their clients.
The network service providers were allocated such space by the RIPE
NCC or the IR, acting for North America and the Pacific Rim. This
process has started to distribute the function of address
registration to a more regional level, closer to the end users. The
process has operated as hoped for, with no major problems.
3. Milestone that has not been met
The proposed schedule of  stated that 6 June 1993 was the date
when an address aggregation mechanism would be generally available in
the Internet. Although this target date was based on the plans as
stated by the router vendors and was reasonable at the time the
schedule in  was formulated, it has slipped. Nevertheless, the
continuation of that schedule has so far not added significantly to
the problems of the Internet. The rest of this document looks at the
current situation and what can be expected in the near future.
4. Current status of address aggregation mechanisms in commercial
Although RFCs 1366, 1466, and 1367 do not depend on any specific
address aggregation technology, there is consensus in the Internet
community to use Classless Inter-Domain Routing (CIDR) . CIDR is
supported by BGP-4 and IDRP. Most router vendors are working on BGP-
4, first, and there is a consensus to use BGP-4 to support the
initial deployment of CIDR in the Internet.
The following paragraphs describe the implementation status and plans
of software to support CIDR in various router vendors' products,
listed in alphabetical order. Some speculation is necessarily
involved in deriving these projections. See also the minutes of the
July 1993 meeting of the BGP Deployment Working Group of the IETF
3Com's BGP-4 code has been tested internally. They have code that
accepts, forwards and manages aggregated routes properly, and they
are ready to test it for interoperability with other vendors. They
have yet to implement the code that forms the route aggregates. They
expect to have Beta code done by September, and full release code
shortly thereafter. The initial implementation will not support de-
aggregation. Their plans here are not yet formulated. They will
support de-aggregation if necessary.
ANS has a BGP-4 implementation that is being tested internally. It
is stable enough to begin testing for interoperability with other
vendors' implementations. Depending of the results of
interoperability testing, this code could be deployed into the ANSNET
by August. This delay is primarily because some routers are running
older code, and they all need to be upgraded to GATED before they can
all support BGP-4 internally. So the ability to support CIDR looks
like it is about one to two months away. This code will not support
controlled de-aggregation, but de-aggregation will be supported if
BBN plans to complete it's development of BGP-4 by early Summer 1994.
Initial plans are to implement both aggregation and controlled de-
aggregation with an early release of the software.
Cisco's BGP-4 implementation is under development at this time.
There is pre-Beta code available for people to begin testing. It is
expected that the code will be stable sometime during the summer of
1993 and will be made available for limited deployment at that time.
This BGP-4 code will implement aggregation. It will not be part of
the normal release cycle at this time. It will be available in a
special software release based on the 9.21 release. This initial
BGP-4 code will not implement controlled de-aggregation, but Cisco
plans on implementing de-aggregation.
Proteon's BGP-4 code has been tested internally. They are ready to
test it for interoperability with other vendors. If this works out
reasonably well, then it is reasonable to expect that they can start
to deploy this as Beta code by August, with a target of full release
in the fall. This initial implementation will not support aggregation
or de-aggregation. Aggregation will be implemented soon thereafter,
but their plans for de-aggregation are not yet formulated. They will
implement de-aggregation if necessary.
Wellfleet is aiming at having beta code implementing BGP-4 roughly in
early 1994. This code will include controlled de-aggregation.
5. Rate of growth
MERIT periodically publishes the number of networks in the
NSFNET/ANSNET policy routing database. Analysis of this data
suggests that the number of entries in this database is growing at
approximately 8% per month, or doubling every nine or ten months .
Although there are currently over 13K networks in the NSFNET/ANSNET
policy routing database, a number of them are not active. That is,
they are not announced to the NSFNET/ANSNET Backbone. The 10K active
network point was passed in late June. Assuming that the number of
active networks continues to grow at the same rate as in the past, it
can be projected that the 12K active network point will be reached
sometime in approximately late September 1993 and that the 25K active
network point will be reached sometime in mid-94 (two high water
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  to
(among other goals) evaluate the impact of CIDR on the growth rate of
router forwarding tables.
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
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
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
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.
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
 Gerich, E., "Guidelines for Management of IP Address Space",
RFC 1366, Merit, October 1992.
 Gerich, E., "Guidelines for Management of IP Address Space",
RFC 1466, Merit, May 1993.
 Topolcic, C., "Schedule for IP Address Space Management
Guidelines", RFC 1367, CNRI, October 1992.
 Fuller, V. et al, "Classless Inter-Domain Routing (CIDR): an
Address Assignment and Aggregation Strategy", working draft
obsoleting RFC 1338, BARRNet, February 1993.
 Yu, J., "Minutes of the BGP Deployment Working Group
(BGPDEPL)", MERIT, July 1993.
 Solensky, F., Internet Growth Charts, "big-internet" mailing
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
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,
Gross, P., and P. Almquist, "IESG Deliberations on Routing and
Addressing", RFC 1380, IESG, November 1992.
10. Security Considerations
Security issues are not discussed in this memo.
11. Author's Address
Corporation for National Research Initiatives
895 Preston White Drive, Suite 100
Reston, VA 22091
Phone: (703) 620-8990