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                       JPNIC Translated Document

Source document: JPNIC REPORT 3
Date of the source: November 1993
Date of the last update of this translation: October 28, 1995

This is a translation of a JPNIC document. JPNIC provides this
translation for convenience of those who can not read Japanese. But it
may contain mis-translations, and is by no means official. One should
consult the source document written in Japanese for detail.
                IP address allocation

  Consumption of IP address

 IP address is one of the most important resource of the Internet, and NIC
is in the charge for allocating the same. However JPNIC is in charge for the
continental IP address allocation.

 IP address is different from domain name and the resource is finite. Within
a short period Internet has had a tremendous growth and it has caused
the serious problem of exhaustion of IP addresses. A couple of years ago, it
was widely recommended to use the class B addresses for reducing the routing
control information. Within an organization subnets were utilized and
it was recommended to have a single routing information for the external
organizations. However, within a 32 bit address space, there are only 16383
class B addresses (Figure 1), and if IP addresses are allocated in this manner
then the problem has to be faced where there will be no more class B address

 On the other hand, the space supported by class C network addresses appear
to be small for most of the organizations and this can be thought as another
factor for the above mentioned problem. Compared to the actual address space
necessary for most of the organizations, class B network address space is
large and this was another reason for the wide use of class B addresses.

 In order to cope with this problem, the initiative for allocating class
C addresses has been taken.

 CIDR and route control

 The technological background lies in CIDR (Classless Inter-Domain
Routing) which was proposed in 1992. CIDR eliminates the conventional
definition of class based network host and it is based on the idea which
corresponds to arbitrary sized networks. In case of CIDR routing control,
the netmask also announces at the same time, and it integrates the routing
information for a part of the total network, which reduces the load of
routing control.

 If this technology gets widespread then the organizations which are presently
connected to the Internet and for whom the class C address is too small and
class B address is too large, can have a reasonable size of address space. This
will cause an efficient use of address space.

 However, at present not all of the TCP/IP related products can cope with
this technology. For that, the following methods are considered.

 o To each organization a number of class C addresss which is equivalent
   to a number that is a power of two will be allocated. By employing this,
   16 class C addresses can be represented by removing the first 20 bits from
   the bit pattern.

 o Within an organization's terminal networks, this will be treated as the
   conventional class C or it might be used as a subnet.

 o Depending on the necessity, the load of routing control will be reduced by
   aggregating the multiple routing information into a single one from the
   Internet side.

 If the above strategies are followed, then by forcing a portion of the router
to correspond to the CIDR, instead of a class B address a number of class C
addresses could be allotted and this would suppress the increasing overhead of
routing control.

 By advancing this idea further, addresses would be allocable by considering
the network topology and the investigation is in progress to enable all
kind of routing. As given in figure 2, the routing information of NSFNET is
enormously increasing. This has already caused a big overhead, and the
prevention of the same has become a big problem. In RFC1466, the scope of
"Pacific Rim" is mentioned as, from to This means
that if this method is applied with routing aggregation then there is a
possibility for reducing routing information. That is, if the first 7 bits are
1100101, then it can be concluded that packets are to be send towards Pacific
Rim. For example a network with an address space from
to can be considered from outside of Pacific Rim as a single
network with net and netmask

 Although at present CIDR is applied to only class C, theoretically it can
also be applied to A and B. However, in that case, all the machines connected
to the network should correspond to CIDR. Therefore it is considered to be
the next step.

 Why 32 bits?

 If the address space consisting of 32 bits is small, then it has to be made
larger, is a natural thought. Of course the investigation for that is going
on. It appears to be a simple problem like replacing the 3 digits exchange
number of the 23 ward of Tokyo to 4 digits. However, compared to the
telephones where the only exchanges are centralized on NTT, in case of the
Internet not only the routers are scattered but also each computer is
basically judging the route. That is, there is a possibility that all the
computers would not be able cope with the modification.

 This kind of large scale modification should have to be handled with
necessary technology which would support all sorts of problems (for example
transportation of a node) related to address formats. The investigation
for this is on progress. In reality it will take some time to put the
things into practice and at present there is no other way than to use the
32bit address space. Although it is not adequate to comment like
this, CIDR seems to have the meaning of gaining time.

 Internet and IP address

 IP address is a must for constructing a network by using TCP/IP technology.
Once an IP address is in use, its modification is very difficult.

 So far, the idea was to obtain a formal address for network operations.
For this, if in future there is the necessity for external connections
then it won't be necessary to change the address. Not only that, even if
the network that requires external connections is an internal part of an
organization, formal address was obtained for preventing troubles.

 More over that, in case of large organizations, there was the idea that it
is easy to operate as a subnet of class A or class B, and for this there was
a tendency to apply for class B addresses.

 However, at present there is a strong tendency to relate IP address to the
Internet on which the whole world is mutually interconnected, and the idea
of thinking it as an address for the connection to the Internet is also

  Allocation of IP address

 The name space of an IP address is fixed and it is totally different from
the variable sized address space of domain name. Please consult a professional
before applying for an IP address. In particular, if there is a plan for
connecting the same to the Internet then please consult a provider.

 The present allocation is based on an estimate of the next 24 months
(2 years) network scale. This is because there is no guarantee that the
present IP address structure would be the same after 5 years.

 Among the class A addresses, addresses from to are not
meant for allocation (reserved). For the time being, it can be thought that
there is no chance for obtaining a new class A address. IANA (Internet
Assigned Numbers Authority) is in charge of allocating class A addresses.

 Based on an estimate of the next 24 months, the conditions for obtaining a
class B address is that there has to be more than 32 subnets, more than
4096 addresses and it has to be proved that it is not possible to construct
the network with class C blocks (32 or 64). The application for class B
address is screened by the Internet Registry (at present InterNIC). Therefore,
the reason for the application has to be written in English. The
applications are screened in a very strict manner. There is no guarantee
for the allocation of a class B address and if the application appears to be
groundless (The estimated number of subnets after 24 months, number of hosts
in the subnet and that the network can not be constructed with class C
blocks should have to be mentioned clearly), then class C blocks will be

 JPNIC forwards the application for class B to the InterNIC but that is only
the case where JPNIC decides that the class B allocation is really necessary.
As the InterNIC screens the documents by considering the remaining address
space, the screening procedure is much more severe than that of JPNIC.
Therefore, if the documents does not pass the screening of JPNIC, and the
applicant send it directly to InterNIC then there is no hope for getting
the allocation.

 JPNIC allocates only class C addresses. One class C address can manage
254 hosts. However, if the convenience for the operation of subnets is
considered then it is difficult to utilize the upper limit of the hosts
which could be managed by a class C address. JPNIC divides the estimated
number of hosts after 24 months by 100 and the number is expressed as
a power of 2, and that is the basis for class C address allocation.
However the upper limit of allocation is set to 64 and if that number is
crossed then it becomes a subject of discussion.

 The technology to deal with IP address is changing rapidly. Therefore,
the applicant might feel that the correspondence from JPNIC is slow and
not kind. However, the procedure for allocating the finite resource to
everyone all around the world in a fair way is not a simple task.

 In the past, the number of application intended for connection to the
Internet was rather small, but as the prerequisite for commercial service
is to get connected to Internet, the applications with the above mentioned
intension have increased.

 IP address is the most important part for the administration of mutual
connectivity to Internet. Because of the growth of the Internet the procedure
for handling the addresses is changing. We seek the understanding and
cooperation from everyone.
                                                        (Shin Yoshimura, IIJ)

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