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This document describes the procedures for the delegation of au-
thority of zones in the domain. As of March
16th 1993 the RIPE NCC has been delegated the authority for the domain from the root. Due to the fact that in
the 193.x.y address space blocks of 256 class C network numbers
are further delegated to local registries , the possibility ex-
ists to also delegate the zone for these blocks in the domain. This document describes some guidelines and
procedures for this type of delegation and the delegation of re-
verse zones for individual class C networks in 193.x.y.

A bit more explained

policies for the assignment of class C network numbers following the CIDR
(RFC 1338) model, in which large chunks of the address space are
delegated to one region, and within that region blocks of class C
network numbers are delegated to service providers and non-
provider registries, some hierarchy in the address space is
created, similar to the hierarchy in the domain name space. Due
to this hierarchy the reverse Domain Name System mapping can also
be delegated in a similar model as used for the normal Domain
Name System. For instance, the RIPE NCC has been assigned the
complete class C address space starting with 193. It is there-
fore possible to delegate the domain completely
to the RIPE NCC, instead of each and every reverse mapping in the domain to be registered with the INTERNIC. This
implies that all resistrations will be done by
the RIPE NCC. Even better, since service providers receive com-
plete class C network blocks from the RIPE NCC, the RIPE NCC can
delegate the reverse registrations for such complete blocks to
these local registries. This implies that customers of these
service providers no longer have to register their reverse domain
mapping with the root, but the service provider have authority
over that part of the reverse mapping. This decreases the work-
load on the INTERNIC and the RIPE NCC, and at the same time in-
crease the service a provider can offer its customers by improve
response times for reverse mapping changes . However there are
some things that need to be examined a bit more closely to avoid
confusion and inconsistencies. These issues are covered in the
next section.

Procedures for the delegation of direct subdomains of

1. A secondary nameserver at is mandatory for all
blocks of class C network numbers delegated in the domain.

2. Because of the increasing importance of correct reverse ad-
dress mapping, for all delegated blocks a good set of secondaries
must be defined. There should be at least 2 nameservers for all
blocks delegated, excluding the RIPE NCC secondary.

3. The delegation of a class C block in the
domain can be requested by sending in a domain object for the
RIPE database to <[email protected]> with all necessary contact
and nameserver information.
globally unique Autonomous System (AS) Numbers within the RIPE NCC service region. These policies are developed by the RIPE Community following the RIPE Policy Development Process.


1.0 Definition Link: #Definition

2.0 Assignment Criteria Link: #AssignmentCriteria

3.0 Returning AS Numbers Link: #Returning

4.0 Transferring AS Numbers Link: #Transferring

5.0 32-bit AS Numbers Link: #ASnumbers

6.0 Registration Link: #Registration

7.0 References Link: #References

8.0 Attribution Link: #Attribution

1.0 Definition

An Autonomous System (AS) is a group of IP networks run by one or more network operators with a single clearly defined routing policy. When exchanging exterior routing information, each AS is identified by a unique number. Exterior routing protocols such as BGP, described in RFC1771 Link: , "A Border Gateway Protocol 4 (BGP-4)", are used to exchange routing information between Autonomous Systems. An AS will normally use some interior gateway protocol to exchange routing information on its internal networks.

2.0 Assignment Criteria

In order to help decrease global routing complexity, a new AS Number should be used only if a new external routing policy is required, see RFC1930 Link: .

A network must be multihomed in order to qualify for an AS Number.

When requesting an AS Number the routing policy of the Autonomous System must be provided. The new unique routing policy should be defined in RPSL language, as used in the RIPE Database.

The RIPE NCC will then forward all
current reverse zones inside this block to the registry, and
after addition of these by the registry, the NCC will check the
working of the reverse server. Once everything is setup proper-
ly, the NCC will delegate the block, and submit the database ob-
ject for inclusion in the database. An example domain object can
be found at the end of this document.

4. All reverse servers for blocks must be reachable from the
whole of the Internet. In short, all servers must meet similar
connectivity requirements as top-level domain servers.

5. Running the reverse server for class C blocks does not imply
that one controls that part of the reverse domain, it only im-
plies that one administers that part of the reverse domain.

6. Before adding individual nets, the administrator of a reverse
domain must check wether all servers to be added for these nets
are indeed setup properly.

7. There are some serious implications when a customer of a ser-
vice provider that uses address space out of the service provider
class C blocks, moves to another service provider. The previous
service provider cannot force its ex-customer to change network
addresses, and will have to continue to provide the appropriate
delegation records for reverse mapping of these addresses, even
though it they are no longer belonging to a customer.

8. The registration of the reverse zones for individual class C
networks will usually be done by the registry administering the
class C block this network has been assigned from. The registry
will make the necessary changes to the zone, and update the net-
work objects in the RIPE database for these networks, to reflect
the correct "rev-srv" fields. In case the RIPE NCC receives a
request for the reverse zone of an individual class C network out
of a block that has been delegated, the request will be forwarded
to the zone contact for this reverse block.

9. The NCC advises the following timers and counters for direct
subdomains of 8 hours refresh (28800 seconds),
2 hours retry (7200 seconds), 7 days expire (604800 seconds) and
1 day Time To Live (86400 seconds). The retry counter should be
lowered where connectivity is unstable.

Above procedures are defined to ensure the necessary high availa-
bility for the 193 reverse domains, and to minimize confusion.
The NCC will ensure fast repsonse times for addition requests,
and will in principle update the domain at least
once per working day.

Example domain object to request a block delegation

descr: Pan European Organisations class C block
admin-c: Daniel Karrenberg
tech-c: Marten Terpstra
zone-c: Marten Terpstra
changed: [email protected] 930319
source: RIPE

Procedures for the delegation of individual network zones by the

The registration of the reverse zones for individual class C net-
works will usually be done by the registry administering the
class C block this network has been assigned from. In case the
zone corresponding to the class C block has not been delegated,
assign the AS Number directly to the End User upon a request properly submitted to the RIPE NCC either directly or through a sponsoring LIR. AS Number assignments are subject to the policies described in the RIPE NCC document entitled “Contractual Requirements for Provider Independent Resource Holders in the RIPE NCC Service Region Link: ”.

3.0 Returning AS Numbers

If an organisation no longer uses the AS Number, it should be returned to the public pool of AS Numbers. The RIPE NCC can then reassign the AS Number to another organisation.

4.0 Transferring AS Numbers

Any holder of Autonomous System (AS) Numbers is allowed to re-assign AS Numbers that were previously assigned to them by the RIPE NCC or otherwise through the Regional Internet Registry System.

AS Numbers may only be re-assigned in accordance with the RIPE Policy, “Contractual Requirements for Provider Independent Resource Holders in the RIPE NCC Service Region Link: ”.

Re-assignments must be reflected in the RIPE Database. This re-assignment can either be on a permanent or non-permanent basis.

The RIPE NCC will record the change of AS Numbers after the transfer.

The RIPE NCC will automatically add the reverse nameserver as
specified in the "rev-srv" attribute of the RIPE database object
for this network, using the following procedures:

1. Because of the increasing importance of correct reverse ad-
dress mapping, for all delegated networks a good set of secon-
daries must be defined. There should be at least two nameservers
for all networks delegated.

2. The "rev-srv" field should ONLY contain one fully qualified
domain name of a nameserver which is authoritative for the re-
verse zone for this network.

3. If a network has or is going to have any external connectivi-
ty, it is strongly recommended that it has at least one reverse
nameserver that can be reached from all of the Internet.

4. The checking and addition of the reverse zones for single net-
works is completely automated at the RIPE NCC. Although we do
our best to check the setup of the nameservers, these does not
receive the same level of scrutiny as nameservers for blocks of
class C network numbers. It is the responsibility of the network
contacts to ensure proper operation.

5. Any problems regarding the reverse zones in
should be directed to <[email protected]>.

The NCC also suggests that similar procedures are set up for the
delegation of reverse zones for individual class C networks from
the registries to individual organisations.
publish a separate list of all AS Numbers transferred under this section. The publication shall occur on monthly basis or more frequently if the RIPE NCC so chooses.

The list will contain information about approved and non-approved transfers.

The following information will be published for approved transfers:

  • The name of the transferring party
  • The name(s) of the receiving party or parties
  • The transferred AS Number
  • The date each AS Number was transferred

Non-approved transfers will be published in aggregate statistics. In the statistics the following information will be published:

  • The Number of requested transfers not approved after the RIPE NCC's evaluation
  • The sum of the AS Numbers included in the requested transfers

Neither the AS Numbers nor the organisations involved will be identified in these statistics.

Please note that the transferring party always remains responsible for the AS Number it receives from the RIPE NCC until the transfer of the resource to another party is completed or if the resource is returned.

Re-assigned AS Numbers are no different from AS Numbers assigned directly by the RIPE NCC and so must be used by the receiving party according to the policies described in this document.

5.0 32-bit AS Numbers

The RIPE NCC assigns 32-bit AS Numbers according to the following timeline:

  • From 1 January 2007 the RIPE NCC will process applications that specifically request 32-bit only AS Numbers (AS Numbers that can not be represented with 16 bits) and assign such AS Numbers as requested by the applicant. In the absence of any specific request for a 32-bit only AS Number, the RIPE NCC will assign a 16-bit AS Number.
  • From 1 January 2009 the RIPE NCC will process applications that specifically request 16-bit AS Numbers and assign such AS Numbers as requested by the applicant. In the absence of any specific request for a 16-bit AS Number, the RIPE NCC will assign a 32-bit only AS Number.
  • From 1 January 2010 the RIPE NCC will cease to make any distinction between 16-bit AS Numbers and 32-bit only AS Numbers, and it will operate AS Number assignments from an undifferentiated 32-bit AS Number allocation pool.

6.0 Registration

The RIPE NCC will register the resources issued in the RIPE Database.

7.0 References

[RFC1771] "A Border Gateway Protocol 4 (BGP-4)" Link:

[RFC1930] " Guidelines for creation, selection, and registration of an Autonomous System (AS)" Link:

[RFC2026] "The Internet Standards Process -- Revision 3 IETF Experimental RFC Link: see Sec. 4.2.1

8.0 Attribution

This document is compiled from policies developed by the RIPE community.

The following people actively contributed by making proposals through the RIPE Policy Development Process:

Nick Hilliard, Geoff Huston