APNIC-0xx
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Special Guidelines for Allocation and Assignment for Network 61
Issued: November 26, 1997
Expires: N/A
ABSTRACT
In order to encourage a transition to the classless use of former
class A address space, APNIC has initiated a temporary test period
during which APNIC members and their customers can make use of subnets
of class A addresses. Additional allocation and assignment procedures
described in this document will apply during this test period.
Background
Before the introduction of classless inter-domain routing CIDR
[RFC1519], the unicast IP address space was divided into three ranges
called class A, B, and C each associated with a routing prefix length
of 8, 16 and 24 bits respectively. In this context IP addresses are
often called class A, B or C addresses depending on the range:
0.0.0.0 - 127.255.255.255 used to be called class A addresses
128.0.0.0 - 191.255.255.255 used to be called class B addresses
192.0.0.0 - 223.255.255.255 used to be called class C addresses
There were two more ranges reserved initially. For the understanding
of this document they are irrelevant.
With CIDR, the prefix length information is carried in the routing
protocols and it is technically insignificant which particular range
an address belongs to. For the readability of this document however,
we will use the historic terms class A, class B and class C.
As long as classful routing protocols or obsolete TCP/IP host
implementations are being used, the class (as implied by the
particular range) of the address can become significant because either
it determines prefix length in routing or other assumptions are being
made from the class of the address. Classful software can be
configured to work properly by using subnetting [RFC950] or basing
configurations on the prefix length implied by the address class.
The Internet registries, regional and local, have been assigning
addresses out of the class C range for the last years because this was
believed to cause the least problems with obsolete classful software
on the perimeter of the Internet.
However there is only a limited amount of unallocated class C address
space available. More than 50% of the class C address space is
allocated and some parts of the remaining ranges are reserved by IANA.
Currently the largest amount of unallocated addresses is in class A
space. Therefore regional Internet registries will at some point have
to use allocations from this range.
In April 1995 an experiment started to find out if classless use of
class A addresses would create any significant problems with respect
to routing. The aim of this experiment is described in RFC1797. The
experiment ran for 6 months and was considered a success. The results
of this experiment are described in RFC1879 including possible
problems and solutions.
APNIC Network 61 Experiment
To promote the use of classless addressing the APNIC has taken the
initiative to give members in its service region a choice of
allocations either from class C or class A space. At the 3rd APNIC
meeting held in Kuala Lumpur in June, 1997 the APNIC community
welcomed this initiative and expressed their interest in assigning
class A addresses to their customers. There was consensus that in
order to encourage usage of class A address space, additional
allocation and assignment guidelines should be implemented for a fixed
period of time.
The following sections will describe the special allocation procedures
APNIC utilizes for the Network 61 experiment. These procedures have
been approved by the IANA and are in use in a similar experiment
within the RIPE-NCC community.
Special Allocation Rules
From the issuance of this document until December 31, 1999, special
guidelines will apply to the allocation and assignment of class A
address space. These guidelines are additions to the regular
allocation procedures.
During this time any organisation established as an APNIC member may
request an additional allocation of class A address space. Thus, for
a limited amount of time any ISP can hold two allocations of the same
size: one from class C address space (currently 202.0.0.0/7 and
210.0.0.0/7) and one from the APNIC class A space (61.0.0.0/8).
In order to limit the adverse effect of these special allocations on
routing table growth, global routing annnouncements for this address
space should be kept to an absolute minimum. Ideally each allocation
will be announced via just one prefix. Additional prefixes should
only be announced globally if this is technically absolutely
necessary.
Once an ISP has obtained an allocation from class A space in addition
to an existing allocation from class C space the following rules
apply:
1. If the address space from a class A allocation is entirely
assigned, another class A allocation can be requested.
2. If the address space from a class C allocation is entirely
assigned, another class A or class C allocation can be requested.
This means that an ISP can have two class A allocations or one
allocation of each class but never two class C allocations.
After the expiration of the special period, the usual allocation
policies will apply, i. e., every ISP can only hold one open
allocation at a time. This means that first all allocations the ISP
has at the point in time of the request must be 75% consumed before
additional address space can be allocated.
If the ISP has at the time of the request decided that it will not
continue assigning from class A address space, it has the option of
returning the whole range of class A addresses allocated to it. It
can then request an additional class C allocation once the previously
allocated class C addresses are entirely assigned.
Special Assignment Guidelines
In order to motivate not only ISPs but also end users to use class A
address space in their networks, special assignment policies apply
until the end of the experiment period (December 31, 1999):
1. A temporary assignment from class A space in addition to an
already existing assignment can be made without detailed
documentation so that the end-user can experiment with these
addresses. If the end-user does not have an assignment yet, the
assignment will have to be made according to the normal
procedures.
2. This additional assignment can have up to the same size of
the total previously assigned address space but not more than a
/19.
3. The class A address space must be returned by the end-user to
the appropriate Internet registry 6 months after the assignment or
the usage of the addresses must be documented properly according
to normal assignment rules.
The duration of a temporary assignement can be agreed with
the end-user and/or specified by the ISP. The validity of
the assignment expires in any case at end of December 31,
1999.
If the ISP decides to continue to assign addresses from a
class A space allocation, then the assignments have to be
converted to regular assignments. Otherwise the entire
allocation must be returned to APNIC
The conversion to a regular assignment involves completing
and filing documentation according to the "ISP IP Address
Request Form" and adjusting the size of the assignment if
necessary. The documentation does not need to be submitted
to APNIC. However, APNIC may decide to review it at any
time. Note: As per these rules address space assignments
can be justified by returning an equivalent amount of
addresses as well as by documenting new use.
4. The ISP is obliged to clearly inform the address space user
about the special rules that apply to the additional assignment
before it is made. ISPs are encouraged to advise users to plan
ahead.
5. All assignments no matter from which allocation must be
registered in the APNIC database also during the special period.
Conclusion
In order to promote classless addressing and to make more efficient
use of the remaining unallocated address space, APNIC has proposed to
give members the chance to prepare for the final transition to
classless addressing and the use of class A address space.
This document proposes to create special guidelines for addresses from
class A space until the end of December, 1999. After this period it is
expected that more ISPs will be prepared to assign class A address
space to their customers as as well as to their own networks.