Sample IPv6 Transition Scenarios
The Junos OS supports many IPv6 transition scenarios required by Junos OS customers. The following are selected examples:
Example 1: IPv4 Depletion with a Non-IPv6 Access Network
Figure 1 depicts a scenario in which the Internet service provider (ISP) has not significantly changed its IPv4 network. This approach enables IPv4 hosts to access the IPv4 Internet and IPv6 hosts to access the IPv6 Internet. A dual-stack host can be treated as an IPv4 host when it uses the IPv4 access service, and as an IPv6 host when it uses the IPv6 access service.
Two new types of devices must be deployed in this approach: a dual-stack home gateway and a dual-stack carrier-grade Network Address Translation (NAT). The dual-stack home gateway integrates IPv4 forwarding and v6-over-v4 tunneling functions. It can also integrate a v4-v4 NAT function. The dual-stack carrier-grade NAT (CGN) integrates v6-over-v4 tunneling and carrier-grade v4-v4 NAT functions.
Example 2: IPv4 Depletion with an IPv6 Access Network
In the scenario shown in Figure 2, the ISP network is IPv6-only.
The dual-stack lite (DS-Lite) solution accommodates IPv6-only ISPs. The best business model for this approach is that the customer premises equipment (CPE) has integrated the functions for tunneling IPv6 to an IPv4 backbone, tunneling IPv4 to an IPv6 backbone, and can automatically detect which solution is required.
Not all customers of a given ISP must switch from IPv4 access to IPv6 access simultaneously; in fact, transition can be managed better by switching groups of customers (for example, all those connected to a single point of presence) on an incremental basis. Such an incremental approach should prove easier to plan, schedule, and execute than an across-the-board conversion.
Example 3: IPv4 Depletion for Mobile Networks
The complexity of mobile networks necessitates a flexible migration approach to ensure minimal disruption and maximum backward compatibility during transition. NAT64 can be used to enable IPv6 devices to communicate to IPv4 hosts without modifying the clients.