Eric - Fred has the model right. The CPE router (actually a gateway with
router/firewall/DHCP/DNS services) uses DHCPv6 PD (prefix delegation; RFC
3633) to obtain a prefix (either a /64 or shorter) and then assigns /64
prefixes to any downstream links. The devices in the home use either
autonomous address selection or DHCPv6 for address assignment and DHCPv6 for
other configuration information. Those devices use DDNS - either in the
gateway or provided by the ISP - to announce any publicly accessible
The net effect is that a customer can plug in a gateway and then devices on
the downstream links from the gateway without any hands-on configuration by
either the customer or the ISP. There seems to be pretty broad consensus
among ISPs that this model describes the initial version of IPv6 service.
Check out draft-vandevelde-v6ops-nap-00.txt for more thoughts about why NATs
are in use today and how IPv6 provides the same functions.
As Fred says, the IETF continues to identify specific needs - in this case,
the need for minimal overhead to both the customer and the ISP for IPv6
service - get buy-in from the interested parties and develop solutions and
standards for protocols that can meet those needs, such as the RFCs and
Internet Drafts we've referred to in this thread...
At 10:29 AM 11/22/2004 -0800, Fred Baker wrote:
At 12:35 PM 11/22/04 -0500, Eric A. Hall wrote:
One potentially technical hurdle here is the way that the device
discovers that a range/block of addresses is available to it. Some kind
of DHCP sub-lease, or maybe a collection of options (is it a range of
addresses or an actual subnet? how big is it, and does that include
net/bcast addresses?),is going to be required.
I think you're saying that the router/firewall/gateway thingie needs to
have some sequence like:
- initial boot or expiration of previous lease occurs
- CPE router has or forms link-local association with upstream router
(note that a non-link-local address on the upstream interface is optional)
- CPE router sends DHCP request for configuration
- upstream router replies with address of DHCP server, DNS Server, and a
prefix with a lease. It also configures itself with a local route to that
prefix via CPE router.
- CPE router configures interior interface with said prefix and starts some
combination of autoconfiguration and DHCP configuration of downstream
- If Dynamic DNS is in use, some hosts may advise the DNS server of their
new address. If there is a management contract (ISP knows about and does
something with the CPE router), supplying the router's address upstream is
one possible use of DDNS.
Note that in the case that DDNS is in use and we are triggering off lease
expiration, the process needs to take the concepts and issues of
I have added Ralph Droms to this. Ralph, your suggestion?
So it would obviously be useful that Linksys et al make sure that the
specs are there to help them continue providing the same kind of
high-value low-management experience. This is the kind of cross-industry
participation I'm talking about needing.
I'll argue that this is pretty much what the IETF has always done. It
comes down to "someone who sees the need propose a solution and make sure
the other folks who are likely to be interested buy into it". It is
fundamental to what we do.
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