Abstract

Introduction

This document describes the policy for reverse delegation of IPv4 and IPv6 address space in the RIPE NCC service region.

Contents

1.0 Introduction Link: #intro
2.0 Obtaining Delegation of an in-addr.arpa or ip6.arpa sub-domain Link: #delegation
3.0 Procedures Link: #procedures
4.0 References Link: #references

1.0 Introduction

The RIPE NCC provides, as part of its services, the necessary support to enable the reverse resolution of IPv4 and IPv6 address space into domain names. This service is implemented under the in-addr.arpa and ip6.arpa sub-domains described in [1 Link: #references ] and [2 Link: #references ].

Reverse delegations for IPv4 and IPv6 addresses allocated by the RIPE NCC are made to Local Internet Registries (LIRs) and further delegated by the LIRs to Internet Service Providers or End Users.

2.0 Obtaining Delegation of an in-addr.arpa or ip6.arpa sub-domain

The RIPE NCC provides reverse delegation for address space that has been allocated or assigned by the RIPE NCC. It also provides systems to control reverse delegations relating to early registrations that have been transferred to the RIPE Database. Registrants of address space allocations or assignments may delegate authority for requesting reverse delegation from the RIPE NCC.

The RIPE NCC accepts requests for reverse delegation for address space that has been allocated by the RIPE NCC to an LIR or, in the case of PI address space, an assignment that has been made to an End User.

3.0 Procedures

The procedures for requesting and modifying reverse delegation and information about the requirements the RIPE NCC enforces to maintain the quality of the reverse delegations are published at:

http://www.ripe.net/reverse/ Link: /manage-ips-and-asns/dns/reverse-dns/

4.0 References

[1] "Management Guidelines & Operational Requirements for the Address and Routing Parameter Area Domain ("arpa")"
[RFC 3172 Link: ftp://ftp.ripe.net/rfc/rfc3172.txt ]

[2] "DNS Extensions to Support IPv6 Address Aggregation and Renumbering" [RFC 2874 Link: ftp://ftp.ripe.net/rfc/rfc2874.txt ]

A bit more explained

With 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 therefore possible to delegate the 193.in-addr.arpa domain completely to the RIPE NCC, instead of each and every reverse mapping in the 193.in-addr.arpa domain to be registered with the INTERNIC. This implies that all 193.in-addr.arpa resistrations will be done by the RIPE NCC. Even better, since service providers receive complete 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 workload on the INTERNIC and the RIPE NCC, and at the same time increase 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 193.in-addr.arpa

1. A secondary nameserver at ns.ripe.net is mandatory for all blocks of class C network numbers delegated in the 193.in-addr.arpa domain.

2. Because of the increasing importance of correct reverse address 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 193.in-addr.arpa domain can be requested by sending in a domain object for the RIPE database to <[email protected]> with all necessary contact and nameserver information. 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 properly, the NCC will delegate the block, and submit the database object 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 implies 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 service 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 network 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 193.in-addr.arpa: 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 availability 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 193.in-addr.arpa domain at least once per working day.

Example domain object to request a block delegation

domain: 202.193.in-addr.arpa
descr: Pan European Organisations class C block
admin-c: Daniel Karrenberg
tech-c: Marten Terpstra
zone-c: Marten Terpstra
nserver: ns.eu.net
nserver: sunic.sunet.se
nserver: ns.ripe.net
changed: [email protected] 930319
source: RIPE

Procedures for the delegation of individual network zones by the RIPE NCC.

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. In case the zone corresponding to the class C block has not been delegated, 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 address mapping, for all delegated networks a good set of secondaries 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 reverse zone for this network.

3. If a network has or is going to have any external connectivity, 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 networks 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 193.in-addr.arpa 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.