IPv6 Internet

As discussed, the 6bone is an IPv6 backbone used for testing purposes. The 6bone runs using the IPv6 test address space 3ffe::/16, and its operation is based on best effort.

However, to build and deploy a reliable production IPv6 Internet around the world, the IPv6 must be able to provide production IPv6 address spaces to ISPs. Since 1999, RIRs have been allocating IPv6 production prefixes to ISPs.

This section provides information about production IPv6 address allocation policy, criteria to become an IPv6 Tier-1 provider, and address space reassignment to customers.

Regional Internet Registries

The IANA initially allocated the aggregatable global unicast IPv6 address space 2001::/16 for the production purposes of the IPv6 Internet.

As with IPv4, this IPv6 production address space is managed by the three RIRs located in different regions of the world:

• APNIC— Asia Pacific Network Information Center. Covers Asia and Australia.

• ARIN— American Registry for Internet Numbers. Covers North America, Central America, and South America.

• RIPE NCC— Réseaux IP Européens Network Coordination Center. Covers Europe and the Middle East.

ISPs can receive upon request their IPv6 production space from those registries. The addresses are free, but the registries generally charge a price for the service.

The Registries' IPv6 Address Allocation Policy

As with the 6bone, the production IPv6 address allocation policy has evolved over time. The allocation policy is identical for all registries except for the prices and management. The policy was reviewed by the IETF and by a public consultation process. Prefixes are allocated only to ISPs, not to enterprises.

The initial address allocation of production IPv6 prefixes began in July 1999, and the current allocation policy was adopted in July 2002.

Initial 1999 Allocation Policy

The initial allocation policy of production IPv6 addresses was adopted in July 1999. The initial policy was based on a slow-start process in which regional Internet registries allocated /35 prefixes to ISPs. By allocating smaller address space to new ISPs, this slow-start process allowed registries to conserve IPv6 address space.

A bootstrap procedure was defined to help new ISPs meet the initial criteria of this allocation policy. The criteria were based on past experience of ISPs with IPv4. Therefore, the policy helped groups of ISPs deploy IPv6 before enforcing permanent rules.

In 2001, work started to review the initial allocation policy toward the development of a general allocation policy that all RIRs can apply. The initial allocation policy is now outdated with the enforcement of the new policy in July 2002.

Current Allocation Policy

The current allocation policy for production IPv6 addresses is defined in the document “IPv6 Address Allocation and Assignment Policy.” It can be found on the APNIC, ARIN, and RIPE NCC web sites using these links:

• APNIC— ftp.apnic.net/apnic/docs/ipv6-address-policy

• ARIN— www.arin.net/policy/ipv6_policy.html

• RIPE NCC— www.ripe.net/ripe/docs/ipv6policy.html

The current policy contains the following initial criteria:

• Be a Local Internet Registry (LIR)— A LIR is an Internet registry that primarily assigns address space to the users of the network services it provides. LIRs are generally ISPs whose customers are primarily end users and possibly other ISPs.

• Do not be an end site— An end site is an end user (subscriber) who has a business relationship with an ISP.

• Plan to provide IPv6 connectivity to organizations— The provider should assign at least one /48 prefix per organization.

• Plan to assign 200 /48 prefixes within two years— The /48 prefixes should be assigned to organizations (end sites) within two years.

Then, the address allocation policy states that organizations (ISPs) that meet the initial criteria are eligible to receive a minimum allocation of /32. Organizations that hold a /35 prefix received from the initial allocation policy are automatically entitled to receive a /32 prefix. The /32 prefix contains the /35 prefix that was already allocated.

According to this allocation policy, it is possible for a provider to qualify for an initial allocation greater than /32 by submitting justifications. In this case, the allocation of addresses is based on the number of existing users and the extent of the organization's infrastructure.

It is also possible for a provider to request additional address space. Subsequent allocation criteria have been defined for this purpose. These criteria are based on the use of the /48 assignments realized by the providers. The HD ratio (as presented in RFC 3194, The Host-Density Ratio for Address Assignment Efficiency: An update on the H ratio) is used to determine which threshold justifies the additional address space required.

Address Space Reassignment to Customers

The allocation policy also defines rules for the reassignment of address space to customers. These rules are based on the guidelines defined in RFC 3177, IAB/IESG Recommendations on IPv6 Address Allocations to Sites, and in the document “IPv6 Initial Request for IP Address Space.” The allocation policy contains the following rules:

• Customer prefix length— In general, the IPv6 prefix assigned to a customer (end site) by a provider should be a /48. However, larger prefixes may be assigned to very large subscribers.

• Subnet prefix length— One /64 prefix may be assigned to a subnet only when it is known that one and only one subnet is needed in the design. Home networks and small networks designed with only one subnet are examples of /64 prefix assignments.

• Device prefix length— One /128 prefix may be assigned to a device only when it is absolutely known that one and only one device is connecting. A single PC, PDA, or cell phone that dials up from a remote location and uses a PPP connection are examples of /128 prefix assignments.

Address Allocation

As with the 6bone, boundaries are defined in the address allocation policy within the production aggregatable global unicast IPv6 prefix 2001::/16. Figure 7-6 illustrates the assignments between the prefix 2001::/16 and the end sites. The first level shown is the prefix of the production IPv6 address space assigned by IANA. It is followed by the RIR allocation. 16 bits are available for the RIR level, so RIRs can allocate the initial /32 prefix to each ISP. Finally, ISPs assign /48 prefixes to each customer (end site).

Figure 7-7 shows a hierarchical view of the address allocation. On the RIR level, APNIC receives the prefixes 2001:02xx::/23 and 2001:0cxx::/23, ARIN receives the 2001:04xx::/23 prefix and RIPE NCC receives 2001:06xx::/23. On the next level, /32 prefixes of the address spaces received by RIRs are allocated to ISPs and then /48 prefixes are assigned to sites (customers).