• Router Discovery: used since there is no default gateway configuration:
• Every host must discover a router by sending out "Router Solicitation" messages.
• Routers will respond with a "Solicited Router Advertisement".
• Routers will also send out "Router Advertisements" at regular intervals.
• Router advertisements contain:
• The link-local address of the router;
• Info about the link (e.g. default hop limit);
• Router lifetime;
• What addresses exist on this link (e.g. global or ULA).

• SLAAC: StateLess Auto Address Configuration:

1. Generate interface ID and create link-local address (i.e. EUI-64);
2. Discover prefix on link through Router Advertisement messages;
3. Verify address uniqueness (DAD: Duplicate Address Detection).

• DHCPv6: is not mandatory:
• Stateful DHCPv6 keeps state of client address leases;
• Provides additional information (e.g. DNS server, domain, etc.);
• Similar to IPv4 DHCP (some message types have changed);
• Stateful DHCPv6 is not commonly available in IPv6 stacks.

• Address Resolution: IPv6 neighbour discovery:
• Send out "Neighbour Solicitation" message.
• Receive "Neighbour Advertisement" reply.

• Transition Phases:
• Phase 1 - Early Adopters: IPv6 in IPv4 tunnelling from the home.
• Phase 2 - Distributed IPv6 over Ethernet for unicast services.
• Phase 3 - IPv6 over Ethernet for unicast and multicast services.

• NAT444: (LSN - Large Scale NAT)

• No change required to CPE.
• Have to be careful of:
• Address overlaps between customer's RFC1918 addresses and the provider-assigned RFC1918 addresses.
• Routing between end subscribers -- can use:
• Hairpinning.
• SP shared addresses.

• NAT 64 + DNS64:

• NAT464:

• Is closer to a pure IPv6 network than NAT444.
• Eases the burden of having to assign and manage both IPv4 and IPv6 addresses on links.
• Because of translation between IPv4 and IPv6 address families:
• Is more complex than NAT444.
• Doesn't perform or scale as well as NAT444.

• DS Lite: (Dual Stack Lite)

• Uses IPv6-only links between the customer and the provider.
• Tunnels IPv4 traffic over IPv6.
• The LSN performing the NAT44 has to also track the source address of the encapsulating IPv6 packet.
• Disadvantage is that CPE needs to be upgraded (either software or hardware), but may not be a big problem:
• It is new customers who are creating demand for new IP addresses.
• Existing customers can be upgraded as part of normal hardware refresh or churn cycles.
• DS Lite can also run in the protocol stack on an individual end system -- useful for:
• Single PC, laptop, gaming systems connected to the Internet.
• Mobile broadband.

• NAT type comparison:

• Dual Stack: The only real problem with this is how can you dual stack if you've run out of IPv4 addresses?
• Therefore: must start to dual stack before running out of IPv4 addresses.

• Migration Options:
• Dual stack: network runs both stacks, effectively "ships in the night".
• 6over4: IPv6 tunneled over an IPv4 backbone.
• 6PE: IPv6 tunneled over an IPv4/MPLS backbone.
• 6VPE: same as 6PE, but additionally supports multiple VRFs on the PE routers.
• DS-Lite.
• 6RD.
• NAT64/DNS64.

Various IPv6-Related RFCs

• RFC5569: IPv6 Rapid Deployment on IPv4 Infrastructures (6rd)