Deploying IPv6 in Broadband Access Networks by Asadullah Salman Ahmed Adeel & Salman Asadullah

Author:Asadullah, Salman, Ahmed, Adeel & Salman Asadullah
Language: eng
Format: epub
Publisher: John Wiley & Sons, Inc.
Published: 2011-08-22T16:00:00+00:00

5.1 IPv6 SUPPORT ON GATEWAY ROUTERS

If the SP does not offer IPv6 services to its customers, several options are available to end users to obtain IPv6 connectivity. Customers can begin by upgrading hosts and other devices to dual-stack mode. By upgrading the hosts to dual-stack status, customers can connect to other IPv6 networks, including the IPv6 Internet, by tunneling their IPv6 traffic over the existing IPv4 SP infrastructure. A dual-stack GWR deployed between their hosts and the device that connects them to the SP network can provide customers with multiple options for tunneling IPv6 traffic from the GWR to other IPv6 devices.

Figure 5.2 illustrates a typical IPv6 deployment scenario where the customer has deployed a dual-stack GWR to connect to the IPv6 Internet over an IPv4 infrastructure.

In the example above, the end customer has deployed a dual-stack GWR to connect to the IPv6 Internet by tunneling all IPv6 traffic over the SP IPv4 infrastructure. The GWR receives a public IPv4 address from the SP DHCP server on its WAN interface connected to the SP network. It acts as a DHCP client on its upstream (WAN) interface and acts as a DHCP server on its downstream (LAN) interface, as illustrated in Figure 5.1. The dual-stack host on the LAN receives its private IPv4 address from the GWR and uses the GWR as its default gateway for forwarding all IPv4 traffic.

The end customer can sign up for any of the IPv6 services available on the Internet to get IPv6 connectivity. Based on the type of IPv6 service the customer receives, the GWR can be configured accordingly to initiate a tunnel to the IPv6 service router to carry IPv6 traffic over the SP network. The tunnel is terminated on the IPv6 service router, which can route the customer’s IPv6 traffic to the IPv6 Internet, and vice versa. One thing to note is that both tunnel endpoints (source and destination) can be the IPv4 addresses of the GWR WAN interface and the dual-stack IPv6 service router. Once the tunnel comes up on IPv4, the GWR can receive an IPv6 address on its tunnel interface via either SLAAC or DHCPv6. For manual tunnels, the IPv6 address can also be statically assigned to the GWR. If the customer has multiple LAN segments connected to the GWR, the customer can request shorter than /64 prefixes from the IPv6 service provider. The GWR can act as a DHCP-PD requesting router (RR) and request a prefix to be delegated from the IPv6 service provider. The prefix can be assigned from a DHCP-PD delegating router (DR) acting as a DHCPv6 server or a DHCPv6 server located elsewhere in the SP network. Once the GWR receives the delegated prefix, it can subdivide the prefix into smaller chunks of /64 and send out RA messages on its LAN interfaces advertising the /64 IPv6 prefixes that can be used by the hosts to configure themselves with an IPv6 address. The hosts can use the GWR as their IPv6 default gateway. The GWR can forward traffic between the host and the IPv6 Service Router.

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